Java API Manual

Writing Verticles


As was described in the main manual, a verticle is the execution unit of Vert.x.

To recap, Vert.x is a container which executes packages of code called Verticles, and it ensures that the code in the verticle is never executed concurrently by more than one thread. You can write your verticles in any of the languages that Vert.x supports, and Vert.x supports running many verticle instances concurrently in the same Vert.x instance.

All the code you write in a Vert.x application runs inside a Verticle instance.

For simple prototyping and trivial tasks you can write raw verticles and run them directly on the command line, but in most cases you will always wrap your verticles inside Vert.x modules.

For now, let's try writing a simple raw verticle.

As an example we'll write a simple TCP echo server. The server just accepts connections and any data received by it is echoed back on the connection.

Copy the following into a text editor and save it as Server.java

import org.vertx.java.core.Handler;
import org.vertx.java.core.net.NetSocket;
import org.vertx.java.core.streams.Pump;
import org.vertx.java.platform.Verticle;

public class Server extends Verticle {

  public void start() {
    vertx.createNetServer().connectHandler(new Handler<NetSocket>() {
      public void handle(final NetSocket socket) {
        Pump.createPump(socket, socket).start();
      }
    }).listen(1234);
  }
}

Now run it:

vertx run Server.java

The server will now be running. Connect to it using telnet:

telnet localhost 1234

And notice how data you send (and hit enter) is echoed back to you.

Congratulations! You've written your first verticle.

Notice how you didn't have to first compile the .java file to a .class file. Vert.x understands how to run .java files directly - internally doing the compilation on the fly. (It also supports running .class files too if you prefer)

Every Java verticle must extend the class org.vertx.java.deploy.Verticle. You must override the start method - this is called by Vert.x when the verticle is started.

In the rest of this manual we'll assume the code snippets are running inside a verticle.

Asynchronous start


In some cases your Verticle has to do some other stuff asynchronously in its start() method, e.g. start other verticles, and the verticle shouldn't be considered started until those other actions are complete.

If this is the case for your verticle you can implement the asynchronous version of the start() method:

public void start(final Future<Void> startedResult) {
  // For example - deploy some other verticle
  container.deployVerticle("foo.js", new AsyncResultHandler<String>() {
    public void handle(AsyncResult<String> deployResult) {
      if (deployResult.succeeded()) {
        startedResult.setResult(null);
      } else {
        startedResult.setFailure(deployResult.cause());
      }
    }
  });
}

Verticle clean-up


Servers, clients, event bus handlers and timers will be automatically closed / cancelled when the verticle is stopped. However, if you have any other clean-up logic that you want to execute when the verticle is stopped, you can implement a stop method which will be called when the verticle is undeployed.

The container object


Each verticle instance has a member variable called container. This represents the Verticle's view of the container in which it is running.

The container object contains methods for deploying and undeploying verticle and modules, and also allows config, environment variables and a logger to be accessed.

The vertx object


Each verticle instance has a member variable called vertx. This provides access to the Vert.x core API. You'll use the Core API to do most things in Vert.x including TCP, HTTP, file system access, event bus, timers etc.

Getting Configuration in a Verticle


You can pass configuration to a module or verticle from the command line using the -conf option, for example:

vertx runmod com.mycompany~my-mod~1.0 -conf myconf.json

or for a raw verticle

vertx run foo.js -conf myconf.json

The argument to -conf is the name of a text file containing a valid JSON object.

That configuration is available inside your verticle by calling the config() method on the container member variable of the verticle:

JsonObject config = container.config();

System.out.println("Config is " + config);

The config returned is an instance of org.vertx.java.core.json.JsonObject, which is a class which represents JSON objects (unsurprisingly!). You can use this object to configure the verticle.

Allowing verticles to be configured in a consistent way like this allows configuration to be easily passed to them irrespective of the language that deploys the verticle.

Logging from a Verticle


Each verticle is given its own logger. To get a reference to it invoke the logger() method on the container instance:

Logger logger = container.logger();

logger.info("I am logging something");

The logger is an instance of the class org.vertx.java.core.logging.Logger and has the following methods;

  • trace
  • debug
  • info
  • warn
  • error
  • fatal

Which have the normal meanings you would expect.

The log files by default go in a file called vertx.log in the system temp directory. On my Linux box this is \tmp.

For more information on configuring logging, please see the main manual.

Accessing environment variables from a Verticle


You can access the map of environment variables from a Verticle with the env() method on the container object.

Causing the container to exit


You can call the exit() method of the container to cause the Vert.x instance to make a clean shutdown.

Deploying and Undeploying Verticles Programmatically


You can deploy and undeploy verticles programmatically from inside another verticle. Any verticles deployed this way will be able to see resources (classes, scripts, other files) of the main verticle.

Deploying a simple verticle


To deploy a verticle programmatically call the function deployVerticle on the container variable.

To deploy a single instance of a verticle :

container.deployVerticle(main);

Where main is the name of the Verticle (i.e. the name of the Java file or FQCN of the class).

See the chapter on "running Vert.x" in the main manual for a description of what a main is.

Deploying Worker Verticles


The deployVerticle method deploys standard (non worker) verticles. If you want to deploy worker verticles use the deployWorkerVerticle method. This method takes the same parameters as deployVerticle with the same meanings.

Deploying a module programmatically


You should use deployModule to deploy a module, for example:

container.deployModule("io.vertx~mod-mailer~2.0.0-beta1", config);

Would deploy an instance of the io.vertx~mod-mailer~2.0.0-beta1 module with the specified configuration. Please see the modules manual for more information about modules.

Passing configuration to a verticle programmatically


JSON configuration can be passed to a verticle that is deployed programmatically. Inside the deployed verticle the configuration is accessed with the config() method. For example:

JsonObject config = new JsonObject();
config.putString("foo", "wibble");
config.putBoolean("bar", false);
container.deployVerticle("foo.ChildVerticle", config);

Then, in ChildVerticle you can access the config via config() as previously explained.

Using a Verticle to co-ordinate loading of an application


If you have an appplication that is composed of multiple verticles that all need to be started at application start-up, then you can use another verticle that maintains the application configuration and starts all the other verticles. You can think of this as your application starter verticle.

For example, you could create a verticle AppStarter as follows:

// Application config

JsonObject appConfig = container.config();

JsonObject verticle1Config = appConfig.getObject("verticle1_conf");
JsonObject verticle2Config = appConfig.getObject("verticle2_conf");
JsonObject verticle3Config = appConfig.getObject("verticle3_conf");
JsonObject verticle4Config = appConfig.getObject("verticle4_conf");
JsonObject verticle5Config = appConfig.getObject("verticle5_conf");

// Start the verticles that make up the app

container.deployVerticle("verticle1.js", verticle1Config);
container.deployVerticle("verticle2.rb", verticle2Config);
container.deployVerticle("foo.Verticle3", verticle3Config);
container.deployWorkerVerticle("foo.Verticle4", verticle4Config);
container.deployWorkerVerticle("verticle5.js", verticle5Config, 10);

Then create a file 'config.json" with the actual JSON config in it

{
    "verticle1_conf": {
        "foo": "wibble"
    },
    "verticle2_conf": {
        "age": 1234,
        "shoe_size": 12,
        "pi": 3.14159
    },
    "verticle3_conf": {
        "strange": true
    },
    "verticle4_conf": {
        "name": "george"
    },
    "verticle5_conf": {
        "tel_no": "123123123"
    }
}

Then set the AppStarter as the main of your module and then you can start your entire application by simply running:

vertx runmod com.mycompany~my-mod~1.0 -conf config.json

If your application is large and actually composed of multiple modules rather than verticles you can use the same technique.

More commonly you'd probably choose to write your starter verticle in a scripting language such as JavaScript, Groovy, Ruby or Python - these languages have much better JSON support than Java, so you can maintain the whole JSON config nicely in the starter verticle itself.

Specifying number of instances


By default, when you deploy a verticle only one instance of the verticle is deployed. Verticles instances are strictly single threaded so this means you will use at most one core on your server.

Vert.x scales by deploying many verticle instances concurrently.

If you want more than one instance of a particular verticle or module to be deployed, you can specify the number of instances as follows:

container.deployVerticle("foo.ChildVerticle", 10);

Or

container.deployModule("io.vertx~some-mod~1.0", 10);

The above examples would deploy 10 instances.

Getting Notified when Deployment is complete


The actual verticle deployment is asynchronous and might not complete until some time after the call to deployVerticle or deployModule has returned. If you want to be notified when the verticle has completed being deployed, you can pass a handler as the final argument to deployVerticle or deployModule:

container.deployVerticle("foo.ChildVerticle", new AsyncResultHandler<String>() {
    public void handle(AsyncResult<String> asyncResult) {
        if (asyncResult.succeeded()) {
            System.out.println("The verticle has been deployed, deployment ID is " + asyncResult.result());
        } else {
            asyncResult.cause().printStackTrace();
        }
    }
});

The handler will get passed an instance of AsyncResult when it completes. You can use the methods succeeded() and failed() on AsyncResult to see if the operation completed ok.

The method result() provides the result of the async operation (if any) which in this case is the deployment ID - you will need this if you need to subsequently undeploy the verticle / module.

The method cause() provides the Throwable if the action failed.

Undeploying a Verticle or Module


Any verticles or modules that you deploy programmatically from within a verticle, and all of their children are automatically undeployed when the parent verticle is undeployed, so in many cases you will not need to undeploy a verticle manually, however if you do need to do this, it can be done by calling the method undeployVerticle or undeployModule passing in the deployment id.

container.undeployVerticle(deploymentID);

You can also provide a handler to the undeploy method if you want to be informed when undeployment is complete.

Scaling your application


A verticle instance is almost always single threaded (the only exception is multi-threaded worker verticles which are an advanced feature), this means a single instance can at most utilise one core of your server.

In order to scale across cores you need to deploy more verticle instances. The exact numbers depend on your application - how many verticles there are and of what type.

You can deploy more verticle instances programmatically or on the command line when deploying your module using the -instances command line option.

The Event Bus


The event bus is the nervous system of Vert.x.

It allows verticles to communicate with each other irrespective of what language they are written in, and whether they're in the same Vert.x instance, or in a different Vert.x instance.

It even allows client side JavaScript running in a browser to communicate on the same event bus. (More on that later).

The event bus forms a distributed peer-to-peer messaging system spanning multiple server nodes and multiple browsers.

The event bus API is incredibly simple. It basically involves registering handlers, unregistering handlers and sending and publishing messages.

First some theory:

The Theory


Addressing


Messages are sent on the event bus to an address.

Vert.x doesn't bother with any fancy addressing schemes. In Vert.x an address is simply a string, any string is valid. However it is wise to use some kind of scheme, e.g. using periods to demarcate a namespace.

Some examples of valid addresses are europe.news.feed1, acme.games.pacman, sausages, and X.

Handlers


A handler is a thing that receives messages from the bus. You register a handler at an address.

Many different handlers from the same or different verticles can be registered at the same address. A single handler can be registered by the verticle at many different addresses.

Publish / subscribe messaging


The event bus supports publishing messages. Messages are published to an address. Publishing means delivering the message to all handlers that are registered at that address. This is the familiar publish/subscribe messaging pattern.

Point to point and Request-Response messaging


The event bus supports point to point messaging. Messages are sent to an address. Vert.x will then route it to just one of the handlers registered at that address. If there is more than one handler registered at the address, one will be chosen using a non-strict round-robin algorithm.

With point to point messaging, an optional reply handler can be specified when sending the message. When a message is received by a recipient, and has been handled, the recipient can optionally decide to reply to the message. If they do so that reply handler will be called.

When the reply is received back at the sender, it too can be replied to. This can be repeated ad-infinitum, and allows a dialog to be set-up between two different verticles. This is a common messaging pattern called the Request-Response pattern.

Transient


All messages in the event bus are transient, and in case of failure of all or parts of the event bus, there is a possibility messages will be lost. If your application cares about lost messages, you should code your handlers to be idempotent, and your senders to retry after recovery.

If you want to persist your messages you can use a persistent work queue module for that.

Types of messages


Messages that you send on the event bus can be as simple as a string, a number or a boolean. You can also send Vert.x buffers or JSON messages.

It's highly recommended you use JSON messages to communicate between verticles. JSON is easy to create and parse in all the languages that Vert.x supports.

Event Bus API


Let's jump into the API.

Registering and Unregistering Handlers


To set a message handler on the address test.address, you do something like the following:

EventBus eb = vertx.eventBus();

Handler<Message> myHandler = new Handler<Message>() {
    public void handle(Message message) {
        System.out.println("I received a message " + message.body);
    }
};

eb.registerHandler("test.address", myHandler);

It's as simple as that. The handler will then receive any messages sent to that address.

The class Message is a generic type and specific Message types include Message<Boolean>, Message<Buffer>, Message<byte[]>, Message<Byte>, Message<Character>, Message<Double>, Message<Float>, Message<Integer>, Message<JsonObject>, Message<JsonArray>, Message<Long>, Message<Short> and Message<String>.

If you know you'll always be receiving messages of a particular type you can use the specific type in your handler, e.g:

Handler<Message<String>> myHandler = new Handler<Message<String>>() {
    public void handle(Message<String> message) {
        String body = message.body;
    }
};

The return value of registerHandler is the Event Bus itself, i.e. we provide a fluent API so you can chain multiple calls together.

When you register a handler on an address and you're in a cluster it can take some time for the knowledge of that new handler to be propagated across the entire cluster. If you want to be notified when that has completed you can optionally specify another handler to the registerHandler method as the third argument. This handler will then be called once the information has reached all nodes of the cluster. E.g. :

eb.registerHandler("test.address", myHandler, new AsyncResultHandler<Void>() {
    public void handle(AsyncResult<Void> asyncResult) {
        System.out.println("The handler has been registered across the cluster ok? " + asyncResult.succeeded());
    }
});

To unregister a handler it's just as straightforward. You simply call unregisterHandler passing in the address and the handler:

eb.unregisterHandler("test.address", myHandler);

A single handler can be registered multiple times on the same, or different, addresses so in order to identify it uniquely you have to specify both the address and the handler.

As with registering, when you unregister a handler and you're in a cluster it can also take some time for the knowledge of that unregistration to be propagated across the entire to cluster. If you want to be notified when that has completed you can optionally specify another function to the registerHandler as the third argument. E.g. :

eb.unregisterHandler("test.address", myHandler, new AsyncResultHandler<Void>() {
    public void handle(AsyncResult<Void> asyncResult) {
        System.out.println("The handler has been unregistered across the cluster ok? " + asyncResult.succeeded());
    }
});

If you want your handler to live for the full lifetime of your verticle there is no need to unregister it explicitly - Vert.x will automatically unregister any handlers when the verticle is stopped.

Publishing messages


Publishing a message is also trivially easy. Just publish it specifying the address, for example:

eb.publish("test.address", "hello world");

That message will then be delivered to all handlers registered against the address "test.address".

Sending messages


Sending a message will result in only one handler registered at the address receiving the message. This is the point to point messaging pattern. The handler is chosen in a non strict round-robin fashion.

eb.send("test.address", "hello world");

Replying to messages


Sometimes after you send a message you want to receive a reply from the recipient. This is known as the request-response pattern.

To do this you send a message, and specify a reply handler as the third argument. When the receiver receives the message they can reply to it by calling the reply method on the message.. When this method is invoked it causes a reply to be sent back to the sender where the reply handler is invoked. An example will make this clear:

The receiver:

Handler<Message<String>> myHandler = new Handler<Message<String>>() {
    public void handle(Message<String> message) {
        System.out.println("I received a message " + message.body);

        // Do some stuff

        // Now reply to it

        message.reply("This is a reply");
    }
};

eb.registerHandler("test.address", myHandler);

The sender:

eb.send("test.address", "This is a message", new Handler<Message<String>>() {
    public void handle(Message<String> message) {
        System.out.println("I received a reply " + message.body);
    }
});

It is legal also to send an empty reply or a null reply.

The replies themselves can also be replied to so you can create a dialog between two different verticles consisting of multiple rounds.

Specifying timeouts for replies


If you send a message specifying a reply handler, and the reply never comes, then, by default, you'll be left with a handler that never gets unregistered.

To remedy this you can also specify a Handler<AsyncResult<Message>> as a reply handler and a timeout in ms. If a reply is received before timeout your handler will be called with an AsyncResult containing the message, but if no reply is received before timeout, the handler will be automatically unregistered and your handler will be called with a failed result so you can deal with it in your code.

Here's an example:

eb.sendWithTimeout("test.address", "This is a message", 1000, new Handler<AsyncResult<Message<String>>>() {
    public void handle(AsyncResult<Message<String>> result) {
        if (result.succeeded()) {
            System.out.println("I received a reply " + message.body);
        } else {

            System.err.println("No reply was received before the 1 second timeout!");
        }
    }
});

If the send times out, the exception it is available with the cause() method of the AsyncResult is of type ReplyException. The return value failureType() on the ReplyException instance is ReplyFailure.TIMEOUT.

You can also set a default timeout on the event bus itself - this timeout will be used if you are using the send(...) method on the event bus to send messages with a reply handler. The default value of the default timeout is -1 which means that reply handlers will never timeout (this is for backward compatibility reasons with earlier versions of Vert.x).

eb.setDefaultReplyTimeout(5000);

eb.send("test.address", "This is a message", new Handler<Message<String>>() {
    public void handle(Message<String> message) {
        System.out.println("I received a reply before the timeout of 5 seconds");
    }
});

When replying to messages you can also provide a timeout and a Handler<AsyncResult<Message>> to get replies to the replies within a timeout. The API used is similar to before:

message.replyWithTimeout("This is a reply", 1000, new Handler<AsyncResult<Message<String>>>() {
    public void handle(AsyncResult<Message<String>> result) {
        if (result.succeeded()) {
            System.out.println("I received a reply to the reply" + message.body);
        } else {
            System.err.println("No reply to the reply was received before the 1 second timeout!");
        }
    }
});

Getting notified of reply failures


If you send a message with a timeout and result handler, and there are no handlers available to send the message to, the handler will be called with a failed AsyncResult where the cause() is a ReplyException. The return value failureType() on the ReplyException instance is ReplyFailure.NO_HANDLERS.

If you send a message with a timeout and result handler, and the recipent of the message responds by calling Message.fail(..), the handler will be called with a failed AsyncResult where the cause() is a ReplyException. The return value failureType() on the ReplyException instance is ReplyFailure.RECIPIENT_FAILURE.

For example

eb.registerHandler("test.address", new Handler<Message<String>>() {
    public void handle(Message<String> message) {
        message.fail(123, "Not enough aardvarks");
    }
});

eb.sendWithTimeout("test.address", "This is a message", 1000, new Handler<AsyncResult<Message<String>>>() {
    public void handle(AsyncResult<Message<String>> result) {
        if (result.succeeded()) {
            System.out.println("I received a reply " + message.body);
        } else {
            ReplyException ex = (ReplyException)result.cause();
            System.err.println("Failure type: " + ex.failureType();
            System.err.println("Failure code: " + ex.failureCode();
            System.err.println("Failure message: " + ex.message();
        }
    }
});

Message types


The message you send can be any of the following types (or their matching boxed type):

  • boolean
  • byte[]
  • byte
  • char
  • double
  • float
  • int
  • long
  • short
  • java.lang.String
  • org.vertx.java.core.json.JsonObject
  • org.vertx.java.core.json.JsonArray
  • org.vertx.java.core.buffer.Buffer

Vert.x buffers and JSON objects and arrays are copied before delivery if they are delivered in the same JVM, so different verticles can't access the exact same object instance which could lead to race conditions.

Here are some more examples:

Send some numbers:

eb.send("test.address", 1234);
eb.send("test.address", 3.14159);

Send a boolean:

eb.send("test.address", true);

Send a JSON object:

JsonObject obj = new JsonObject();
obj.putString("foo", "wibble");
eb.send("test.address", obj);

Null messages can also be sent:

eb.send("test.address", null);

It's a good convention to have your verticles communicating using JSON - this is because JSON is easy to generate and parse for all the languages that Vert.x supports.

Distributed event bus


To make each Vert.x instance on your network participate on the same event bus, start each Vert.x instance with the -cluster command line switch.

See the chapter in the main manual on running Vert.x for more information on this.

Once you've done that, any Vert.x instances started in cluster mode will merge to form a distributed event bus.

Shared Data


Sometimes it makes sense to allow different verticles instances to share data in a safe way. Vert.x allows simple java.util.concurrent.ConcurrentMap and java.util.Set data structures to be shared between verticles.

There is a caveat: To prevent issues due to mutable data, Vert.x only allows simple immutable types such as number, boolean and string or Buffer to be used in shared data. With a Buffer, it is automatically copied when retrieved from the shared data, so different verticle instances never see the same object instance.

Currently data can only be shared between verticles in the same Vert.x instance. In later versions of Vert.x we aim to extend this to allow data to be shared by all Vert.x instances in the cluster.

Shared Maps


To use a shared map to share data between verticles first we get a reference to the map, and then use it like any other instance of java.util.concurrent.ConcurrentMap

ConcurrentMap<String, Integer> map = vertx.sharedData().getMap("demo.mymap");

map.put("some-key", 123);

And then, in a different verticle you can access it:

ConcurrentMap<String, Integer> map = vertx.sharedData().getMap("demo.mymap");

// etc

Shared Sets


To use a shared set to share data between verticles first we get a reference to the set.

Set<String> set = vertx.sharedData().getSet("demo.myset");

set.add("some-value");

And then, in a different verticle:

Set<String> set = vertx.sharedData().getSet("demo.myset");

// etc

Buffers


Most data in Vert.x is shuffled around using instances of org.vertx.java.core.buffer.Buffer.

A Buffer represents a sequence of zero or more bytes that can be written to or read from, and which expands automatically as necessary to accomodate any bytes written to it. You can perhaps think of a buffer as smart byte array.

Creating Buffers


Create a new empty buffer:

Buffer buff = new Buffer();

Create a buffer from a String. The String will be encoded in the buffer using UTF-8.

Buffer buff = new Buffer("some-string");

Create a buffer from a String: The String will be encoded using the specified encoding, e.g:

Buffer buff = new Buffer("some-string", "UTF-16");

Create a buffer from a byte[]

byte[] bytes = new byte[] { ... };
new Buffer(bytes);

Create a buffer with an initial size hint. If you know your buffer will have a certain amount of data written to it you can create the buffer and specify this size. This makes the buffer initially allocate that much memory and is more efficient than the buffer automatically resizing multiple times as data is written to it.

Note that buffers created this way are empty. It does not create a buffer filled with zeros up to the specified size.

Buffer buff = new Buffer(100000);

Writing to a Buffer


There are two ways to write to a buffer: appending, and random access. In either case buffers will always expand automatically to encompass the bytes. It's not possible to get an IndexOutOfBoundsException with a buffer.

Appending to a Buffer


To append to a buffer, you use the appendXXX methods. Append methods exist for appending other buffers, byte[], String and all primitive types.

The return value of the appendXXX methods is the buffer itself, so these can be chained:

Buffer buff = new Buffer();

buff.appendInt(123).appendString("hello\n");

socket.write(buff);

Random access buffer writes


You can also write into the buffer at a specific index, by using the setXXX methods. Set methods exist for other buffers, byte[], String and all primitive types. All the set methods take an index as the first argument - this represents the position in the buffer where to start writing the data.

The buffer will always expand as necessary to accomodate the data.

Buffer buff = new Buffer();

buff.setInt(1000, 123);
buff.setBytes(0, "hello");

Reading from a Buffer


Data is read from a buffer using the getXXX methods. Get methods exist for byte[], String and all primitive types. The first argument to these methods is an index in the buffer from where to get the data.

Buffer buff = ...;
for (int i = 0; i < buff.length(); i += 4) {
    System.out.println("int value at " + i + " is " + buff.getInt(i));
}

Other buffer methods:


  • length(). To obtain the length of the buffer. The length of a buffer is the index of the byte in the buffer with the largest index + 1.
  • copy(). Copy the entire buffer

See the JavaDoc for more detailed method level documentation.

JSON


Whereas JavaScript has first class support for JSON, and Ruby has Hash literals which make representing JSON easy within code, things aren't so easy in Java.

For this reason, if you want to use JSON from within your Java verticles, we provide some simple JSON classes which represent a JSON object and a JSON array. These classes provide methods for setting and getting all types supported in JSON on an object or array.

A JSON object is represented by instances of org.vertx.java.core.json.JsonObject. A JSON array is represented by instances of org.vertx.java.core.json.JsonArray.

A usage example would be using a Java verticle to send or receive JSON messages from the event bus.

EventBus eb = vertx.eventBus();

JsonObject obj = new JsonObject().putString("foo", "wibble")
                                 .putNumber("age", 1000);

eb.send("some-address", obj);

// ....
// And in a handler somewhere:

public void handle(Message<JsonObject> message) {
    System.out.println("foo is " + message.body.getString("foo");
    System.out.println("age is " + message.body.getNumber("age");
}

Methods also existing for converting this objects to and from their JSON serialized forms.

Please see the JavaDoc for the full Java Json API.

Delayed and Periodic Tasks


It's very common in Vert.x to want to perform an action after a delay, or periodically.

In standard verticles you can't just make the thread sleep to introduce a delay, as that will block the event loop thread.

Instead you use Vert.x timers. Timers can be one-shot or periodic. We'll discuss both

One-shot Timers


A one shot timer calls an event handler after a certain delay, expressed in milliseconds.

To set a timer to fire once you use the setTimer method passing in the delay and a handler

long timerID = vertx.setTimer(1000, new Handler<Long>() {
    public void handle(Long timerID) {
        log.info("And one second later this is printed");
    }
});

log.info("First this is printed");

The return value is a unique timer id which can later be used to cancel the timer. The handler is also passed the timer id.

Periodic Timers


You can also set a timer to fire periodically by using the setPeriodic method. There will be an initial delay equal to the period. The return value of setPeriodic is a unique timer id (long). This can be later used if the timer needs to be cancelled. The argument passed into the timer event handler is also the unique timer id:

long timerID = vertx.setPeriodic(1000, new Handler<Long>() {
    public void handle(Long timerID) {
        log.info("And every second this is printed");
    }
});

log.info("First this is printed");

Cancelling timers


To cancel a periodic timer, call the cancelTimer method specifying the timer id. For example:

long timerID = vertx.setPeriodic(1000, new Handler<Long>() {
    public void handle(Long timerID) {
    }
});

// And immediately cancel it

vertx.cancelTimer(timerID);

Or you can cancel it from inside the event handler. The following example cancels the timer after it has fired 10 times.

long timerID = vertx.setPeriodic(1000, new Handler<Long>() {
    int count;
    public void handle(Long timerID) {
        log.info("In event handler " + count);
        if (++count == 10) {
            vertx.cancelTimer(timerID);
        }
    }
});

Writing TCP Servers and Clients


Creating TCP servers and clients is very easy with Vert.x.

Net Server


Creating a Net Server


To create a TCP server you call the createNetServer method on your vertx instance.

NetServer server = vertx.createNetServer();

Start the Server Listening


To tell that server to listen for connections we do:

NetServer server = vertx.createNetServer();

server.listen(1234, "myhost");

The first parameter to listen is the port. A wildcard port of 0 can be specified which means a random available port will be chosen to actually listen at. Once the server has completed listening you can then call the port() method of the server to find out the real port it is using.

The second parameter is the hostname or ip address. If it is omitted it will default to 0.0.0.0 which means it will listen at all available interfaces.

The actual bind is asynchronous so the server might not actually be listening until some time after the call to listen has returned. If you want to be notified when the server is actually listening you can provide a handler to the listen call. For example:

server.listen(1234, "myhost", new AsyncResultHandler<Void>() {
    public void handle(AsyncResult<NetServer> asyncResult) {
        log.info("Listen succeeded? " + asyncResult.succeeded());
    }
});

Getting Notified of Incoming Connections


To be notified when a connection occurs we need to call the connectHandler method of the server, passing in a handler. The handler will then be called when a connection is made:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(NetSocket sock) {
        log.info("A client has connected!");
    }
});

server.listen(1234, "localhost");

That's a bit more interesting. Now it displays 'A client has connected!' every time a client connects.

The return value of the connectHandler method is the server itself, so multiple invocations can be chained together. That means we can rewrite the above as:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(NetSocket sock) {
        log.info("A client has connected!");
    }
}).listen(1234, "localhost");

or

vertx.createNetServer().connectHandler(new Handler<NetSocket>() {
    public void handle(NetSocket sock) {
        log.info("A client has connected!");
    }
}).listen(1234, "localhost");

This is a common pattern throughout the Vert.x API.

Closing a Net Server


To close a net server just call the close function.

server.close();

The close is actually asynchronous and might not complete until some time after the close method has returned. If you want to be notified when the actual close has completed then you can pass in a handler to the close method.

This handler will then be called when the close has fully completed.

server.close(new AsyncResultHandler<Void>() {
    public void handle(AsyncResult<Void> asyncResult) {
        log.info("Close succeeded? " + asyncResult.succeeded());
    }
});

If you want your net server to last the entire lifetime of your verticle, you don't need to call close explicitly, the Vert.x container will automatically close any servers that you created when the verticle is undeployed.

NetServer Properties


NetServer has a set of properties you can set which affect its behaviour. Firstly there are bunch of properties used to tweak the TCP parameters, in most cases you won't need to set these:

  • setTCPNoDelay(tcpNoDelay) If true then Nagle's Algorithm is disabled. If false then it is enabled.

  • setSendBufferSize(size) Sets the TCP send buffer size in bytes.

  • setReceiveBufferSize(size) Sets the TCP receive buffer size in bytes.

  • setTCPKeepAlive(keepAlive) if keepAlive is true then TCP keep alive is enabled, if false it is disabled.

  • setReuseAddress(reuse) if reuse is true then addresses in TIME_WAIT state can be reused after they have been closed.

  • setSoLinger(linger)

  • setTrafficClass(trafficClass)

NetServer has a further set of properties which are used to configure SSL. We'll discuss those later on.

Handling Data


So far we have seen how to create a NetServer, and accept incoming connections, but not how to do anything interesting with the connections. Let's remedy that now.

When a connection is made, the connect handler is called passing in an instance of NetSocket. This is a socket-like interface to the actual connection, and allows you to read and write data as well as do various other things like close the socket.

Reading Data from the Socket


To read data from the socket you need to set the dataHandler on the socket. This handler will be called with an instance of org.vertx.java.core.buffer.Buffer every time data is received on the socket. You could try the following code and telnet to it to send some data:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(NetSocket sock) {
        sock.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                log.info("I received " + buffer.length() + " bytes of data");
            }
        });
    }
}).listen(1234, "localhost");

Writing Data to a Socket


To write data to a socket, you invoke the write function. This function can be invoked in a few ways:

With a single buffer:

Buffer myBuffer = new Buffer(...);
sock.write(myBuffer);

A string. In this case the string will encoded using UTF-8 and the result written to the wire.

sock.write("hello");

A string and an encoding. In this case the string will encoded using the specified encoding and the result written to the wire.

sock.write("hello", "UTF-16");

The write function is asynchronous and always returns immediately after the write has been queued.

Let's put it all together.

Here's an example of a simple TCP echo server which simply writes back (echoes) everything that it receives on the socket:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {
        sock.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                sock.write(buffer);
            }
        });
    }
}).listen(1234, "localhost");

Socket Remote Address


You can find out the remote address of the socket (i.e. the address of the other side of the TCP IP connection) by calling remoteAddress().

Socket Local Address


You can find out the local address of the socket (i.e. the address of this side of the TCP IP connection) by calling localAddress().

Closing a socket


You can close a socket by invoking the close method. This will close the underlying TCP connection.

Closed Handler


If you want to be notified when a socket is closed, you can set the `closedHandler':

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {
        sock.closedHandler(new VoidHandler() {
            public void handle() {
                log.info("The socket is now closed");
            }
        });
    }
}).listen(1234, "localhost");

The closed handler will be called irrespective of whether the close was initiated by the client or server.

Exception handler


You can set an exception handler on the socket that will be called if an exception occurs asynchronously on the connection:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {
        sock.exceptionHandler(new Handler<Throwable>() {
            public void handle(Throwable t) {
                log.info("Oops, something went wrong", t);
            }
        });
    }
}).listen(1234, "localhost");

Event Bus Write Handler


Every NetSocket automatically registers a handler on the event bus, and when any buffers are received in this handler, it writes them to itself. This enables you to write data to a NetSocket which is potentially in a completely different verticle or even in a different Vert.x instance by sending the buffer to the address of that handler.

The address of the handler is given by the writeHandlerID() method.

For example to write some data to the NetSocket from a completely different verticle you could do:

String writeHandlerID = ... // E.g. retrieve the ID from shared data

vertx.eventBus().send(writeHandlerID, buffer);

Read and Write Streams


NetSocket also implements org.vertx.java.core.streams.ReadStream and org.vertx.java.core.streams.WriteStream. This allows flow control to occur on the connection and the connection data to be pumped to and from other object such as HTTP requests and responses, WebSockets and asynchronous files.

This will be discussed in depth in the chapter on streams and pumps.

Scaling TCP Servers


A verticle instance is strictly single threaded.

If you create a simple TCP server and deploy a single instance of it then all the handlers for that server are always executed on the same event loop (thread).

This means that if you are running on a server with a lot of cores, and you only have this one instance deployed then you will have at most one core utilised on your server!

To remedy this you can simply deploy more instances of the module in the server, e.g.

vertx runmod com.mycompany~my-mod~1.0 -instances 20

Or for a raw verticle

vertx run foo.MyApp -instances 20

The above would run 20 instances of the module/verticle in the same Vert.x instance.

Once you do this you will find the echo server works functionally identically to before, but, as if by magic, all your cores on your server can be utilised and more work can be handled.

At this point you might be asking yourself 'Hold on, how can you have more than one server listening on the same host and port? Surely you will get port conflicts as soon as you try and deploy more than one instance?'

Vert.x does a little magic here.

When you deploy another server on the same host and port as an existing server it doesn't actually try and create a new server listening on the same host/port.

Instead it internally maintains just a single server, and, as incoming connections arrive it distributes them in a round-robin fashion to any of the connect handlers set by the verticles.

Consequently Vert.x TCP servers can scale over available cores while each Vert.x verticle instance remains strictly single threaded, and you don't have to do any special tricks like writing load-balancers in order to scale your server on your multi-core machine.

NetClient


A NetClient is used to make TCP connections to servers.

Creating a Net Client


To create a TCP client you call the createNetClient method on your vertx instance.

NetClient client = vertx.createNetClient();

Making a Connection


To actually connect to a server you invoke the connect method:

NetClient client = vertx.createNetClient();

client.connect(1234, "localhost", new AsyncResultHandler<NetSocket>() {
    public void handle(AsyncResult<NetSocket> asyncResult) {
        if (asyncResult.succeeded()) {
          log.info("We have connected! Socket is " + asyncResult.result());
    } else {
          asyncResult.cause().printStackTrace();
        }
    }
});

The connect method takes the port number as the first parameter, followed by the hostname or ip address of the server. The third parameter is a connect handler. This handler will be called when the connection actually occurs.

The argument passed into the connect handler is an AsyncResult<NetSocket>, and the NetSocket can be retrieved from the result() method. You can read and write data from the socket in exactly the same way as you do on the server side.

You can also close it, set the closed handler, set the exception handler and use it as a ReadStream or WriteStream exactly the same as the server side NetSocket.

Configuring Reconnection


A NetClient can be configured to automatically retry connecting or reconnecting to the server in the event that it cannot connect or has lost its connection. This is done by invoking the methods setReconnectAttempts and setReconnectInterval:

NetClient client = vertx.createNetClient();

client.setReconnectAttempts(1000);

client.setReconnectInterval(500);

ReconnectAttempts determines how many times the client will try to connect to the server before giving up. A value of -1 represents an infinite number of times. The default value is 0. I.e. no reconnection is attempted.

ReconnectInterval detemines how long, in milliseconds, the client will wait between reconnect attempts. The default value is 1000.

NetClient Properties


Just like NetServer, NetClient also has a set of TCP properties you can set which affect its behaviour. They have the same meaning as those on NetServer.

NetClient also has a further set of properties which are used to configure SSL. We'll discuss those later on.

SSL Servers


Net servers can also be configured to work with Transport Layer Security (previously known as SSL).

When a NetServer is working as an SSL Server the API of the NetServer and NetSocket is identical compared to when it working with standard sockets. Getting the server to use SSL is just a matter of configuring the NetServer before listen is called.

To enabled SSL the function setSSL(true) must be called on the Net Server.

The server must also be configured with a key store and an optional trust store.

These are both Java keystores which can be managed using the keytool utility which ships with the JDK.

The keytool command allows you to create keystores, and import and export certificates from them.

The key store should contain the server certificate. This is mandatory - the client will not be able to connect to the server over SSL if the server does not have a certificate.

The key store is configured on the server using the setKeyStorePath() and setKeyStorePassword() methods.

The trust store is optional and contains the certificates of any clients it should trust. This is only used if client authentication is required.

To configure a server to use server certificates only:

NetServer server = vertx.createNetServer()
               .setSSL(true)
               .setKeyStorePath("/path/to/your/keystore/server-keystore.jks")
               .setKeyStorePassword("password");

Making sure that server-keystore.jks contains the server certificate.

To configure a server to also require client certificates:

NetServer server = vertx.createNetServer()
               .setSSL(true)
               .setKeyStorePath("/path/to/your/keystore/server-keystore.jks")
               .setKeyStorePassword("password")
               .setTrustStorePath("/path/to/your/truststore/server-truststore.jks")
               .setTrustStorePassword("password")
               .setClientAuthRequired(true);

Making sure that server-truststore.jks contains the certificates of any clients who the server trusts.

If clientAuthRequired is set to true and the client cannot provide a certificate, or it provides a certificate that the server does not trust then the connection attempt will not succeed.

SSL Clients


Net Clients can also be easily configured to use SSL. They have the exact same API when using SSL as when using standard sockets.

To enable SSL on a NetClient the function setSSL(true) is called.

If the setTrustAll(true) is invoked on the client, then the client will trust all server certificates. The connection will still be encrypted but this mode is vulnerable to 'man in the middle' attacks. I.e. you can't be sure who you are connecting to. Use this with caution. Default value is false.

If setTrustAll(true) has not been invoked then a client trust store must be configured and should contain the certificates of the servers that the client trusts.

The client trust store is just a standard Java key store, the same as the key stores on the server side. The client trust store location is set by using the function setTrustStorePath() on the NetClient. If a server presents a certificate during connection which is not in the client trust store, the connection attempt will not succeed.

If the server requires client authentication then the client must present its own certificate to the server when connecting. This certificate should reside in the client key store. Again it's just a regular Java key store. The client keystore location is set by using the function setKeyStorePath() on the NetClient.

To configure a client to trust all server certificates (dangerous):

NetClient client = vertx.createNetClient()
               .setSSL(true)
               .setTrustAll(true);

To configure a client to only trust those certificates it has in its trust store:

NetClient client = vertx.createNetClient()
               .setSSL(true)
               .setTrustStorePath("/path/to/your/client/truststore/client-truststore.jks")
               .setTrustStorePassword("password");

To configure a client to only trust those certificates it has in its trust store, and also to supply a client certificate:

NetClient client = vertx.createNetClient()
               .setSSL(true)
               .setTrustStorePath("/path/to/your/client/truststore/client-truststore.jks")
               .setTrustStorePassword("password")
               .setClientAuthRequired(true)
               .setKeyStorePath("/path/to/keystore/holding/client/cert/client-keystore.jks")
               .setKeyStorePassword("password");

User Datagram Protocol (UDP)


Using User Datagram Protocol (UDP) with Vert.x is a piece of cake.

UDP is a connection-less transport which basically means you have no persistent connection to a remote peer.

Instead you can send and receive packages and the remote address is contained in each of them.

Beside this UDP is not as safe as TCP to use, which means there are no guarantees that a send Datagram packet will receive it's endpoint at all.

The only guarantee is that it will either receive complete or not at all.

Also you usually can't send data which is bigger then the MTU size of your network interface, this is because each packet will be send as one packet.

But be aware even if the packet size is smaller then the MTU it may still fail.

At which size it will fail depends on the Operating System etc. So rule of thumb is to try to send small packets.

Because of the nature of UDP it is best fit for Applications where you are allowed to drop packets (like for example a monitoring application).

The benefits are that it has a lot less overhead compared to TCP, which can be handled by the NetServer and NetClient (see above).

Creating a DatagramSocket


To use UDP you first need t create a DatagramSocket. It does not matter here if you only want to send data or send and receive.

DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);

The returned DatagramSocket will not be bound to a specific port.

This is not a problem if you only want to send data (like a client), but more on this in the next section.

Sending Datagram packets


As mentioned before, User Datagram Protocol (UDP) sends data in packets to remote peers but is not connected to them in a persistent fashion.

This means each packet can be sent to a different remote peer.

Sending packets is as easy as shown here:

DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);
Buffer buffer = new Buffer("content");
// Send a Buffer
socket.send(buffer, "10.0.0.1", 1234, new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        log.info("Send succeeded? " + asyncResult.succeeded());
    }
});
// Send a String
socket.send("A string used as content", "10.0.0.1", 1234, new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        log.info("Send succeeded? " + asyncResult.succeeded());
    }
});

Receiving Datagram packets


If you want to receive packets you need to bind the DatagramSocket by calling listen(...) on it.

This way you will be able to receive DatagramPackets that were sent to the address and port on which the DatagramSocket listens.

Beside this you also want to set a Handler which will be called for each received DatagramPacket.

The DatagramPacket has the following methods:

  • sender(): The InetSocketAddress which represent the sender of the packet
  • data(): The Buffer which holds the data which was received.

So to listen on a specific address and port you would do something like shown here:

final DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);
socket.listen("0.0.0.0", 1234, new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        if (asyncResult.succeeded()) {
           socket.dataHandler(new Handler<DatagramPacket>() {
                public void handle(DatagramPacket packet) {
                    // Do something with the packet
                }
            });
        } else {
            log.warn("Listen failed", asyncResult.cause());
        }
    }
});

Be aware that even if the AsyncResult is successed it only means it might be written on the network stack, but gives no guarantee that it ever reached or will reach the remote peer at all.

If you need such a guarantee then you want to use TCP with some handshaking logic build on top.

Multicast


Sending Multicast packets


Multicast allows multiple sockets to receive the same packets. This works by have same join a multicast group to which you can send packets.

We will look at how you can joint a Multicast Group and so receive packets in the next section.

For now let us focus on how to send those. Sending multicast packets is not different to send normal Datagram Packets.

The only difference is that you would pass in a multicast group address to the send method.

This is show here:

DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);
Buffer buffer = new Buffer("content");
// Send a Buffer to a multicast address
socket.send(buffer, "230.0.0.1", 1234, new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        log.info("Send succeeded? " + asyncResult.succeeded());
    }
});

All sockets that have joined the multicast group 230.0.0.1 will receive the packet.

Receiving Multicast packets


If you want to receive packets for specific Multicast group you need to bind the DatagramSocket by calling

listen(...) on it and join the Multicast group.

This way you will be able to receive DatagramPackets that were sent to the address and port on which the DatagramSocket listens and also to those sent to the Multicast group.

Beside this you also want to set a Handler which will be called for each received DatagramPacket.

The DatagramPacket has the following methods:

  • sender(): The InetSocketAddress which represent the sender of the packet
  • data(): The Buffer which holds the data which was received.

So to listen on a specific address and port and also receive packets for the Multicast group 230.0.0.1 you would do something like shown here:

final DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);
socket.listen("0.0.0.0", 1234, new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        if (asyncResult.succeeded()) {
            socket.dataHandler(new Handler<DatagramPacket>() {
                public void handle(DatagramPacket packet) {
                    // Do something with the packet
                }
            });

            // join the multicast group
            socket.listenMulticastGroup("230.0.0.1", new AsyncResultHandler<DatagramSocket>() {
                public void handle(AsyncResult<DatagramSocket> asyncResult) {
                    log.info("Listen succeeded? " + asyncResult.succeeded());
                }
            });
        } else {
            log.warn("Listen failed", asyncResult.cause());
        }
    }
});

Unlisten / leave a Multicast group


There are sometimes situations where you want to receive packets for a Multicast group for a limited time.

In this situations you can first start to listen for them and then later unlisten.

This is shown here:

final DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);
socket.listen("0.0.0.0", 1234, new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        if (asyncResult.succeeded()) {
            socket.dataHandler(new Handler<DatagramPacket>() {
                public void handle(DatagramPacket packet) {
                    // Do something with the packet
                }
            });

            // join the multicast group
            socket.listenMulticastGroup("230.0.0.1", new AsyncResultHandler<DatagramSocket>() {
                public void handle(AsyncResult<DatagramSocket> asyncResult) {
                    if (asyncResult.successed()) {

                        // will now receive packets for group
                        ...
                        ...
                        // do some work
                        ..
                        ..
                        socket.unlisten("230.0.0.1", new AsyncResultHandler<DatagramSocket>() {
                            public void handle(AsyncResult<DatagramSocket> asyncResult) {
                                log.info("Unlisten succeeded? " + asyncResult.succeeded());
                            }
                        });

                    } elseĀ {
                       log.warn("Listen failed", asyncResult.cause());
                    }

                }
            });
        } else {
            log.warn("Listen failed", asyncResult.cause());
        }
    }
});

Blocking multicast


Beside unlisten a Multicast address it's also possible to just block multicast for a specific sender address.

Be aware this only work on some Operating Systems and kernel versions. So please check the Operating System documentation if it's supported.

This an expert feature.

To block multicast from a specic address you can call blockMulticastGroup(...) on the DatagramSocket like shown here:

final DatagramSocket socket = vertx.createDatagramSocket(InternetProtocolFamily.IPV4);
...
...
// This would block packets which are send from 10.0.0.2
socket.blockMulticastGroup("230.0.0.1", "10.0.0.2", new AsyncResultHandler<DatagramSocket>() {
    public void handle(AsyncResult<DatagramSocket> asyncResult) {
        log.info("block succeeded? " + asyncResult.succeeded());
    }
});

DatagramSocket properties


When using the DatagramSocket there are multiple properties you can set to change it's behaviour. Those are listed here:

  • setSendBufferSize(size) Sets the send buffer size in bytes.

  • setReceiveBufferSize(size) Sets the TCP receive buffer size in bytes.

  • setReuseAddress(reuse) if reuse is true then addresses in TIME_WAIT state can be reused after they have been closed.

  • setTrafficClass(trafficClass)

  • setBroadcast(broadcast) Sets or clears the SO_BROADCAST socket option. When this option is set, Datagram (UDP) packets may be sent to a local interface's broadcast address.

  • setMulticastLoopbackMode(loopbackModeDisabled) Sets or clears the IP_MULTICAST_LOOP socket option. When this option is set, multicast packets will also be received on the local interface.

  • setMulticastTimeToLive(int ttl) Sets the IP_MULTICAST_TTL socket option. TTL stands for "Time to Live," but in this context it specifies the number of IP hops that a packet is allowed to go through, specifically for multicast traffic. Each router or gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded.

DatagramSocket Local Address


You can find out the local address of the socket (i.e. the address of this side of the UDP Socket) by calling localAddress(). This will only return an InetSocketAddressif you bound theDatagramSocketwithlisten(...)` before, otherwise it will return null.

Closing a DatagramSocket


You can close a socket by invoking the close method. This will close the socket and release all resources

Flow Control - Streams and Pumps


There are several objects in Vert.x that allow data to be read from and written to in the form of Buffers.

In Vert.x, calls to write data return immediately and writes are internally queued.

It's not hard to see that if you write to an object faster than it can actually write the data to its underlying resource then the write queue could grow without bound - eventually resulting in exhausting available memory.

To solve this problem a simple flow control capability is provided by some objects in the Vert.x API.

Any flow control aware object that can be written-to implements org.vertx.java.core.streams.ReadStream, and any flow control object that can be read-from is said to implement org.vertx.java.core.streams.WriteStream.

Let's take an example where we want to read from a ReadStream and write the data to a WriteStream.

A very simple example would be reading from a NetSocket on a server and writing back to the same NetSocket - since NetSocket implements both ReadStream and WriteStream, but you can do this between any ReadStream and any WriteStream, including HTTP requests and response, async files, WebSockets, etc.

A naive way to do this would be to directly take the data that's been read and immediately write it to the NetSocket, for example:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {

        sock.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                // Write the data straight back
                sock.write(buffer);
            }
        });

    }
}).listen(1234, "localhost");

There's a problem with the above example: If data is read from the socket faster than it can be written back to the socket, it will build up in the write queue of the NetSocket, eventually running out of RAM. This might happen, for example if the client at the other end of the socket wasn't reading very fast, effectively putting back-pressure on the connection.

Since NetSocket implements WriteStream, we can check if the WriteStream is full before writing to it:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {

        sock.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                if (!sock.writeQueueFull()) {
                    sock.write(buffer);
                }
            }
        });

    }
}).listen(1234, "localhost");

This example won't run out of RAM but we'll end up losing data if the write queue gets full. What we really want to do is pause the NetSocket when the write queue is full. Let's do that:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {

        sock.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                sock.write(buffer);
                if (sock.writeQueueFull()) {
                    sock.pause();
                }
            }
        });

    }
}).listen(1234, "localhost");

We're almost there, but not quite. The NetSocket now gets paused when the file is full, but we also need to unpause it when the write queue has processed its backlog:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(final NetSocket sock) {

        sock.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                sock.write(buffer);
                if (sock.writeQueueFull()) {
                    sock.pause();
                    sock.drainHandler(new VoidHandler() {
                        public void handle() {
                            sock.resume();
                        }
                    });
                }
            }
        });

    }
}).listen(1234, "localhost");

And there we have it. The drainHandler event handler will get called when the write queue is ready to accept more data, this resumes the NetSocket which allows it to read more data.

It's very common to want to do this when writing Vert.x applications, so we provide a helper class called Pump which does all this hard work for you. You just feed it the ReadStream and the WriteStream and it tell it to start:

NetServer server = vertx.createNetServer();

server.connectHandler(new Handler<NetSocket>() {
    public void handle(NetSocket sock) {
        Pump.create(sock, sock).start();
    }
}).listen(1234, "localhost");

Which does exactly the same thing as the more verbose example.

Let's look at the methods on ReadStream and WriteStream in more detail:

ReadStream


ReadStream is implemented by HttpClientResponse, HttpServerRequest, WebSocket, NetSocket, SockJSSocket and AsyncFile.

Functions:

  • dataHandler(handler): set a handler which will receive data from the ReadStream. As data arrives the handler will be passed a Buffer.
  • pause(): pause the handler. When paused no data will be received in the dataHandler.
  • resume(): resume the handler. The handler will be called if any data arrives.
  • exceptionHandler(handler): Will be called if an exception occurs on the ReadStream.
  • endHandler(handler): Will be called when end of stream is reached. This might be when EOF is reached if the ReadStream represents a file, or when end of request is reached if it's an HTTP request, or when the connection is closed if it's a TCP socket.

WriteStream


WriteStream is implemented by , HttpClientRequest, HttpServerResponse, WebSocket, NetSocket, SockJSSocket and AsyncFile.

Functions:

  • write(buffer): write a Buffer to the WriteStream. This method will never block. Writes are queued internally and asynchronously written to the underlying resource.
  • setWriteQueueMaxSize(size): set the number of bytes at which the write queue is considered full, and the method writeQueueFull() returns true. Note that, even if the write queue is considered full, if write is called the data will still be accepted and queued.
  • writeQueueFull(): returns true if the write queue is considered full.
  • exceptionHandler(handler): Will be called if an exception occurs on the WriteStream.
  • drainHandler(handler): The handler will be called if the WriteStream is considered no longer full.

Pump


Instances of Pump have the following methods:

  • start(): Start the pump.
  • stop(): Stops the pump. When the pump starts it is in stopped mode.
  • setWriteQueueMaxSize(): This has the same meaning as setWriteQueueMaxSize on the WriteStream.
  • bytesPumped(): Returns total number of bytes pumped.

A pump can be started and stopped multiple times.

When a pump is first created it is not started. You need to call the start() method to start it.

Writing HTTP Servers and Clients


Writing HTTP servers


Vert.x allows you to easily write full featured, highly performant and scalable HTTP servers.

Creating an HTTP Server


To create an HTTP server you call the createHttpServer method on your vertx instance.

HttpServer server = vertx.createHttpServer();

Start the Server Listening


To tell that server to listen for incoming requests you use the listen method:

HttpServer server = vertx.createHttpServer();

server.listen(8080, "myhost");

The first parameter to listen is the port.

The second parameter is the hostname or ip address. If it is omitted it will default to 0.0.0.0 which means it will listen at all available interfaces.

The actual bind is asynchronous so the server might not actually be listening until some time after the call to listen has returned. If you want to be notified when the server is actually listening you can provide a handler to the listen call. For example:

server.listen(8080, "myhost", new AsyncResultHandler<Void>() {
    public void handle(AsyncResult<HttpServer> asyncResult) {
        log.info("Listen succeeded? " + asyncResult.succeeded());
    }
});

Getting Notified of Incoming Requests


To be notified when a request arrives you need to set a request handler. This is done by calling the requestHandler method of the server, passing in the handler:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        log.info("A request has arrived on the server!");
        request.response().end();
    }
});

server.listen(8080, "localhost");

Every time a request arrives on the server the handler is called passing in an instance of org.vertx.java.core.http.HttpServerRequest.

You can try it by running the verticle and pointing your browser at http://localhost:8080.

Similarly to NetServer, the return value of the requestHandler method is the server itself, so multiple invocations can be chained together. That means we can rewrite the above with:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        log.info("A request has arrived on the server!");
        request.response().end();
    }
}).listen(8080, "localhost");

Or:

vertx.createHttpServer().requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        log.info("A request has arrived on the server!");
        request.response().end();
    }
}).listen(8080, "localhost");

Handling HTTP Requests


So far we have seen how to create an HttpServer and be notified of requests. Lets take a look at how to handle the requests and do something useful with them.

When a request arrives, the request handler is called passing in an instance of HttpServerRequest. This object represents the server side HTTP request.

The handler is called when the headers of the request have been fully read. If the request contains a body, that body may arrive at the server some time after the request handler has been called.

It contains functions to get the URI, path, request headers and request parameters. It also contains a response() method which returns a reference to an object that represents the server side HTTP response for the object.

Request Method


The request object has a method method() which returns a string representing what HTTP method was requested. Possible return values for method() are: GET, PUT, POST, DELETE, HEAD, OPTIONS, CONNECT, TRACE, PATCH.

Request Version


The request object has a method version() which returns an enum representing the HTTP version.

Request URI


The request object has a method uri() which returns the full URI (Uniform Resource Locator) of the request. For example, if the request URI was:

/a/b/c/page.html?param1=abc&param2=xyz

Then request.uri() would return the string /a/b/c/page.html?param1=abc&param2=xyz.

Request URIs can be relative or absolute (with a domain) depending on what the client sent. In most cases they will be relative.

The request uri contains the value as defined in Section 5.1.2 of the HTTP specification - Request-URI

Request Path


The request object has a method path() which returns the path of the request. For example, if the request URI was:

a/b/c/page.html?param1=abc&param2=xyz

Then request.path() would return the string /a/b/c/page.html

Request Query


The request object has a method query() which contains the query of the request. For example, if the request URI was:

a/b/c/page.html?param1=abc&param2=xyz

Then request.query() would return the string param1=abc&param2=xyz

Request Headers


The request headers are available using the headers() method on the request object.

The returned object is an instance of org.vertx.java.core.MultiMap. A MultiMap allows multiple values for the same key, unlike a normal Map.

Here's an example that echoes the headers to the output of the response. Run it and point your browser at http://localhost:8080 to see the headers.

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        StringBuilder sb = new StringBuilder();
        for (Map.Entry<String, String> header: request.headers().entries()) {
            sb.append(header.getKey()).append(": ").append(header.getValue()).append("\n");
        }
        request.response().putHeader("content-type", "text/plain");
        request.response().end(sb.toString());
    }
}).listen(8080, "localhost");

Request params


Similarly to the headers, the request parameters are available using the params() method on the request object.

The returned object is an instance of org.vertx.java.core.MultiMap.

Request parameters are sent on the request URI, after the path. For example if the URI was:

/page.html?param1=abc&param2=xyz

Then the params multimap would contain the following entries:

param1: 'abc'
param2: 'xyz

Remote Address


Use the method remoteAddress() to find out the address of the other side of the HTTP connection.

Absolute URI


Use the method absoluteURI() to return the absolute URI corresponding to the request.

Reading Data from the Request Body


Sometimes an HTTP request contains a request body that we want to read. As previously mentioned the request handler is called when only the headers of the request have arrived so the HttpServerRequest object does not contain the body. This is because the body may be very large and we don't want to create problems with exceeding available memory.

To receive the body, you set the dataHandler on the request object. This will then get called every time a chunk of the request body arrives. Here's an example:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        request.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                log.info('I received ' + buffer.length() + ' bytes');
            }
        });

    }
}).listen(8080, "localhost");

The dataHandler may be called more than once depending on the size of the body.

You'll notice this is very similar to how data from NetSocket is read.

The request object implements the ReadStream interface so you can pump the request body to a WriteStream. See the chapter on streams and pumps for a detailed explanation.

In many cases, you know the body is not large and you just want to receive it in one go. To do this you could do something like the following:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {

        final Buffer body = new Buffer(0);

        request.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer buffer) {
                body.appendBuffer(buffer);
            }
        });
        request.endHandler(new VoidHandler() {
            public void handle() {
              // The entire body has now been received
              log.info("The total body received was " + body.length() + " bytes");
            }
        });

    }
}).listen(8080, "localhost");

Like any ReadStream the end handler is invoked when the end of stream is reached - in this case at the end of the request.

If the HTTP request is using HTTP chunking, then each HTTP chunk of the request body will correspond to a single call of the data handler.

It's a very common use case to want to read the entire body before processing it, so Vert.x allows a bodyHandler to be set on the request object.

The body handler is called only once when the entire request body has been read.

Beware of doing this with very large requests since the entire request body will be stored in memory.

Here's an example using bodyHandler:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        request.bodyHandler(new Handler<Buffer>() {
            public void handle(Buffer body) {
              // The entire body has now been received
              log.info("The total body received was " + body.length() + " bytes");
            }
        });
    }
}).listen(8080, "localhost");

Handling Multipart Form Uploads


Vert.x understands file uploads submitted from HTML forms in browsers. In order to handle file uploads you should set the uploadHandler on the request. The handler will be called once for each upload in the form.

request.expectMultiPart(true);

request.uploadHandler(new Handler<HttpServerFileUpload>() {
    public void handle(HttpServerFileUpload upload) {
    }
});

The HttpServerFileUpload class implements ReadStream so you read the data and stream it to any object that implements WriteStream using a Pump, as previously discussed.

You can also stream it directly to disk using the convenience method streamToFileSystem().

request.expectMultiPart(true);

request.uploadHandler(new Handler<HttpServerFileUpload>() {
    public void handle(HttpServerFileUpload upload) {
        upload.streamToFileSystem("uploads/" + upload.filename());
    }
});

Handling Multipart Form Attributes


If the request corresponds to an HTML form that was submitted you can use the method formAttributes to retrieve a Multi Map of the form attributes. This should only be called after all of the request has been read - this is because form attributes are encoded in the request body not in the request headers.

request.endHandler(new VoidHandler() {
    public void handle() {
        // The request has been all ready so now we can look at the form attributes
        MultiMap attrs = request.formAttributes();
        // Do something with them
    }
});

HTTP Server Responses


As previously mentioned, the HTTP request object contains a method response(). This returns the HTTP response for the request. You use it to write the response back to the client.

Setting Status Code and Message


To set the HTTP status code for the response use the setStatusCode() method, e.g.

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest request) {
        request.response().setStatusCode(739).setStatusMessage("Too many gerbils").end();
    }
}).listen(8080, "localhost");

You can also use the setStatusMessage() method to set the status message. If you do not set the status message a default message will be used.

The default value for statusCode is 200.

Writing HTTP responses


To write data to an HTTP response, you invoke the write function. This function can be invoked multiple times before the response is ended. It can be invoked in a few ways:

With a single buffer:

Buffer myBuffer = ...
request.response().write(myBuffer);

A string. In this case the string will encoded using UTF-8 and the result written to the wire.

request.response().write("hello");

A string and an encoding. In this case the string will encoded using the specified encoding and the result written to the wire.

request.response().write("hello", "UTF-16");

The write function is asynchronous and always returns immediately after the write has been queued.

If you are just writing a single string or Buffer to the HTTP response you can write it and end the response in a single call to the end method.

The first call to write results in the response header being being written to the response.

Consequently, if you are not using HTTP chunking then you must set the Content-Length header before writing to the response, since it will be too late otherwise. If you are using HTTP chunking you do not have to worry.

Ending HTTP responses


Once you have finished with the HTTP response you must call the end() function on it.

This function can be invoked in several ways:

With no arguments, the response is simply ended.

request.response().end();

The function can also be called with a string or Buffer in the same way write is called. In this case it's just the same as calling write with a string or Buffer followed by calling end with no arguments. For example:

request.response().end("That's all folks");

Closing the underlying connection


You can close the underlying TCP connection of the request by calling the close method.

request.response().close();

Response headers


HTTP response headers can be added to the response by adding them to the multimap returned from the headers() method:

request.response().headers().set("Cheese", "Stilton");
request.response().headers().set("Hat colour", "Mauve");

Individual HTTP response headers can also be written using the putHeader method. This allows a fluent API since calls to putHeader can be chained:

request.response().putHeader("Some-Header", "elephants").putHeader("Pants", "Absent");

Response headers must all be added before any parts of the response body are written.

Chunked HTTP Responses and Trailers


Vert.x supports HTTP Chunked Transfer Encoding. This allows the HTTP response body to be written in chunks, and is normally used when a large response body is being streamed to a client, whose size is not known in advance.

You put the HTTP response into chunked mode as follows:

req.response().setChunked(true);

Default is non-chunked. When in chunked mode, each call to response.write(...) will result in a new HTTP chunk being written out.

When in chunked mode you can also write HTTP response trailers to the response. These are actually written in the final chunk of the response.

To add trailers to the response, add them to the multimap returned from the trailers() method:

request.response().trailers().add("Philosophy", "Solipsism");
request.response().trailers().add("Favourite-Shakin-Stevens-Song", "Behind the Green Door");

Like headers, individual HTTP response trailers can also be written using the putTrailer() method. This allows a fluent API since calls to putTrailer can be chained:

request.response().putTrailer("Cat-Food", "Whiskas").putTrailer("Eye-Wear", "Monocle");

Serving files directly from disk


If you were writing a web server, one way to serve a file from disk would be to open it as an AsyncFile and pump it to the HTTP response. Or you could load it it one go using the file system API and write that to the HTTP response.

Alternatively, Vert.x provides a method which allows you to serve a file from disk to an HTTP response in one operation. Where supported by the underlying operating system this may result in the OS directly transferring bytes from the file to the socket without being copied through userspace at all.

Using sendFile is usually more efficient for large files, but may be slower for small files than using readFile to manually read the file as a buffer and write it directly to the response.

To do this use the sendFile function on the HTTP response. Here's a simple HTTP web server that serves static files from the local web directory:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest req) {
      String file = "";
      if (req.path().equals("/")) {
        file = "index.html";
      } else if (!req.path().contains("..")) {
        file = req.path();
      }
      req.response().sendFile("web/" + file);
    }
}).listen(8080, "localhost");

There's also a version of sendFile which takes the name of a file to serve if the specified file cannot be found:

req.response().sendFile("web/" + file, "handler_404.html");

Note: If you use sendFile while using HTTPS it will copy through userspace, since if the kernel is copying data directly from disk to socket it doesn't give us an opportunity to apply any encryption.

If you're going to write web servers using Vert.x be careful that users cannot exploit the path to access files outside the directory from which you want to serve them.

Pumping Responses


Since the HTTP Response implements WriteStream you can pump to it from any ReadStream, e.g. an AsyncFile, NetSocket, WebSocket or HttpServerRequest.

Here's an example which echoes HttpRequest headers and body back in the HttpResponse. It uses a pump for the body, so it will work even if the HTTP request body is much larger than can fit in memory at any one time:

HttpServer server = vertx.createHttpServer();

server.requestHandler(new Handler<HttpServerRequest>() {
    public void handle(final HttpServerRequest req) {
      req.response().headers().set(req.headers());
      Pump.createPump(req, req.response()).start();
      req.endHandler(new VoidHandler() {
        public void handle() {
            req.response().end();
        }
      });
    }
}).listen(8080, "localhost");

HTTP Compression


Vert.x comes with support for HTTP Compression out of the box. Which means you are able to automatically compress the body of the responses before they are sent back to the Client. If the client does not support HTTP Compression the responses are sent back without compressing the body. This allows to handle Client that support HTTP Compression and those that not support it at the same time.

To enable compression you only need to do:

HttpServer server = vertx.createHttpServer();
server.setCompressionSupported(true);

The default is false.

When HTTP Compression is enabled the HttpServer will check if the client did include an 'Accept-Encoding' header which includes the supported compressions. Common used are deflate and gzip. Both are supported by Vert.x. Once such a header is found the HttpServer will automatically compress the body of the response with one of the supported compressions and send it back to the client.

Be aware that compression may be able to reduce network traffic but is more cpu-intensive.

Writing HTTP Clients


Creating an HTTP Client


To create an HTTP client you call the createHttpClient method on your vertx instance:

HttpClient client = vertx.createHttpClient();

You set the port and hostname (or ip address) that the client will connect to using the setHost and setPort functions:

HttpClient client = vertx.createHttpClient();
client.setPort(8181);
client.setHost("foo.com");

This, of course, can be chained:

HttpClient client = vertx.createHttpClient()
    .setPort(8181)
    .setHost("foo.com");

A single HTTPClient always connects to the same host and port. If you want to connect to different servers, create more instances.

The default port is 80 and the default host is localhost. So if you don't explicitly set these values that's what the client will attempt to connect to.

Pooling and Keep Alive


By default the HTTPClient pools HTTP connections. As you make requests a connection is borrowed from the pool and returned when the HTTP response has ended.

If you do not want connections to be pooled you can call setKeepAlive with false:

HttpClient client = vertx.createHttpClient()
               .setPort(8181)
               .setHost("foo.com").
               .setKeepAlive(false);

In this case a new connection will be created for each HTTP request and closed once the response has ended.

You can set the maximum number of connections that the client will pool as follows:

HttpClient client = vertx.createHttpClient()
               .setPort(8181)
               .setHost("foo.com").
               .setMaxPoolSize(10);

The default value is 1.

Closing the client


Any HTTP clients created in a verticle are automatically closed for you when the verticle is stopped, however if you want to close it explicitly you can:

client.close();

Making Requests


To make a request using the client you invoke one the methods named after the HTTP method that you want to invoke.

For example, to make a POST request:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

HttpClientRequest request = client.post("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        log.info("Got a response: " + resp.statusCode());
    }
});

request.end();

To make a PUT request use the put method, to make a GET request use the get method, etc.

Legal request methods are: get, put, post, delete, head, options, connect, trace and patch.

The general modus operandi is you invoke the appropriate method passing in the request URI as the first parameter, the second parameter is an event handler which will get called when the corresponding response arrives. The response handler is passed the client response object as an argument.

The value specified in the request URI corresponds to the Request-URI as specified in Section 5.1.2 of the HTTP specification. In most cases it will be a relative URI.

Please note that the domain/port that the client connects to is determined by setPort and setHost, and is not parsed from the uri.

The return value from the appropriate request method is an instance of org.vertx.java.core.http.HTTPClientRequest. You can use this to add headers to the request, and to write to the request body. The request object implements WriteStream.

Once you have finished with the request you must call the end() method.

If you don't know the name of the request method in advance there is a general request method which takes the HTTP method as a parameter:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

HttpClientRequest request = client.request("POST", "/some-path/",
    new Handler<HttpClientResponse>() {
        public void handle(HttpClientResponse resp) {
            log.info("Got a response: " + resp.statusCode());
        }
    });

request.end();

There is also a method called getNow which does the same as get, but automatically ends the request. This is useful for simple GETs which don't have a request body:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

client.getNow("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        log.info("Got a response: " + resp.statusCode());
    }
});

Handling exceptions


You can set an exception handler on the HttpClient class and it will receive all exceptions for the client unless a specific exception handler has been set on a specific HttpClientRequest object.

Writing to the request body


Writing to the client request body has a very similar API to writing to the server response body.

To write data to an HttpClientRequest object, you invoke the write function. This function can be called multiple times before the request has ended. It can be invoked in a few ways:

With a single buffer:

Buffer myBuffer = ...
request.write(myBuffer);

A string. In this case the string will encoded using UTF-8 and the result written to the wire.

request.write("hello");

A string and an encoding. In this case the string will encoded using the specified encoding and the result written to the wire.

request.write("hello", "UTF-16");

The write function is asynchronous and always returns immediately after the write has been queued. The actual write might complete some time later.

If you are just writing a single string or Buffer to the HTTP request you can write it and end the request in a single call to the end function.

The first call to write will result in the request headers being written to the request. Consequently, if you are not using HTTP chunking then you must set the Content-Length header before writing to the request, since it will be too late otherwise. If you are using HTTP chunking you do not have to worry.

Ending HTTP requests


Once you have finished with the HTTP request you must call the end function on it.

This function can be invoked in several ways:

With no arguments, the request is simply ended.

request.end();

The function can also be called with a string or Buffer in the same way write is called. In this case it's just the same as calling write with a string or Buffer followed by calling end with no arguments.

Writing Request Headers


To write headers to the request, add them to the multi-map returned from the headers() method:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

HttpClientRequest request = client.post("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        log.info("Got a response: " + resp.statusCode());
    }
});

request.headers().set("Some-Header", "Some-Value");
request.end();

You can also adds them using the putHeader method. This enables a more fluent API since calls can be chained, for example:

request.putHeader("Some-Header", "Some-Value").putHeader("Some-Other", "Blah");

These can all be chained together as per the common Vert.x API pattern:

client.setHost("foo.com").post("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        log.info("Got a response: " + resp.statusCode());
    }
}).putHeader("Some-Header", "Some-Value").end();

Request timeouts


You can set a timeout for specific Http Request using the setTimeout() method. If the request does not return any data within the timeout period an exception will be passed to the exception handler (if provided) and the request will be closed.

HTTP chunked requests


Vert.x supports HTTP Chunked Transfer Encoding for requests. This allows the HTTP request body to be written in chunks, and is normally used when a large request body is being streamed to the server, whose size is not known in advance.

You put the HTTP request into chunked mode as follows:

request.setChunked(true);

Default is non-chunked. When in chunked mode, each call to request.write(...) will result in a new HTTP chunk being written out.

HTTP Client Responses


Client responses are received as an argument to the response handler that is passed into one of the request methods on the HTTP client.

The response object implements ReadStream, so it can be pumped to a WriteStream like any other ReadStream.

To query the status code of the response use the statusCode() method. The statusMessage() method contains the status message. For example:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

client.getNow("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        log.info('server returned status code: ' + resp.statusCode());
        log.info('server returned status message: ' + resp.statusMessage());
    }
});

Reading Data from the Response Body


The API for reading an HTTP client response body is very similar to the API for reading a HTTP server request body.

Sometimes an HTTP response contains a body that we want to read. Like an HTTP request, the client response handler is called when all the response headers have arrived, not when the entire response body has arrived.

To receive the response body, you set a dataHandler on the response object which gets called as parts of the HTTP response arrive. Here's an example:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

client.getNow("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        resp.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer data) {
                log.info('I received ' + buffer.length() + ' bytes');
            }
        });
    }
});

The response object implements the ReadStream interface so you can pump the response body to a WriteStream. See the chapter on streams and pump for a detailed explanation.

The dataHandler can be called multiple times for a single HTTP response.

As with a server request, if you wanted to read the entire response body before doing something with it you could do something like the following:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

client.getNow("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {

        final Buffer body = new Buffer(0);

        resp.dataHandler(new Handler<Buffer>() {
            public void handle(Buffer data) {
                body.appendBuffer(data);
            }
        });
        resp.endHandler(new VoidHandler() {
            public void handle() {
               // The entire response body has been received
               log.info('The total body received was ' + body.length() + ' bytes');
            }
        });
    }
});

Like any ReadStream the end handler is invoked when the end of stream is reached - in this case at the end of the response.

If the HTTP response is using HTTP chunking, then each chunk of the response body will correspond to a single call to the dataHandler.

It's a very common use case to want to read the entire body in one go, so Vert.x allows a bodyHandler to be set on the response object.

The body handler is called only once when the entire response body has been read.

Beware of doing this with very large responses since the entire response body will be stored in memory.

Here's an example using bodyHandler:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

client.getNow("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        resp.bodyHandler(new Handler<Buffer>() {
            public void handle(Buffer body) {
               // The entire response body has been received
               log.info("The total body received was " + body.length() + " bytes");
            }
        });
    }
});

Reading cookies


You can read the list of cookies from the response using the method cookies().

100-Continue Handling


According to the HTTP 1.1 specification a client can set a header Expect: 100-Continue and send the request header before sending the rest of the request body.

The server can then respond with an interim response status Status: 100 (Continue) to signify the client is ok to send the rest of the body.

The idea here is it allows the server to authorise and accept/reject the request before large amounts of data is sent. Sending large amounts of data if the request might not be accepted is a waste of bandwidth and ties up the server in reading data that it will just discard.

Vert.x allows you to set a continueHandler on the client request object. This will be called if the server sends back a Status: 100 (Continue) response to signify it is ok to send the rest of the request.

This is used in conjunction with the sendHead function to send the head of the request.

An example will illustrate this:

HttpClient client = vertx.createHttpClient().setHost("foo.com");

final HttpClientRequest request = client.put("/some-path/", new Handler<HttpClientResponse>() {
    public void handle(HttpClientResponse resp) {
        log.info("Got a response " + resp.statusCode());
    }
});

request.putHeader("Expect", "100-Continue");

request.continueHandler(new VoidHandler() {
    public void handle() {

        // OK to send rest of body
        request.write("Some data").end();
    }
});

request.sendHead();

HTTP Compression


Vert.x comes with support for HTTP Compression out of the box. Which means the HTTPClient can let the remote Http server know that it supports compression, and so will be able to handle compressed response bodies. A Http server is free to either compress with one of the supported compression algorithm or send the body back without compress it at all. So this is only a hint for the Http server which it may ignore at all.

To tell the Http server which compression is supported by the HttpClient it will include a 'Accept-Encoding' header with the supported compression algorithm as value. Multiple compression algorithms are supported. In case of Vert.x this will result in have the following header added:

Accept-Encoding: gzip, deflate

The Http Server will choose then from one of these. You can detect if a HttpServer did compress the body by checking for the 'Content-Encoding' header in the response sent back from it.

If the body of the response was compressed via gzip it will include for example the following header:

Content-Encoding: gzip

To enable compression you only need to do:

HttpClient client = vertx.createHttpClient();
client.setTryUseCompression(true);

The default is false.

Pumping Requests and Responses


The HTTP client and server requests and responses all implement either ReadStream or WriteStream. This means you can pump between them and any other read and write streams.

HTTPS Servers


HTTPS servers are very easy to write using Vert.x.

An HTTPS server has an identical API to a standard HTTP server. Getting the server to use HTTPS is just a matter of configuring the HTTP Server before listen is called.

Configuration of an HTTPS server is done in exactly the same way as configuring a NetServer for SSL. Please see SSL server chapter for detailed instructions.

HTTPS Clients


HTTPS clients can also be very easily written with Vert.x

Configuring an HTTP client for HTTPS is done in exactly the same way as configuring a NetClient for SSL. Please see SSL client chapter for detailed instructions.

Scaling HTTP servers


Scaling an HTTP or HTTPS server over multiple cores is as simple as deploying more instances of the verticle. For example:

vertx runmod com.mycompany~my-mod~1.0 -instance 20

Or, for a raw verticle:

vertx run foo.MyServer -instances 20

The scaling works in the same way as scaling a NetServer. Please see the chapter on scaling Net Servers for a detailed explanation of how this works.

Routing HTTP requests with Pattern Matching


Vert.x lets you route HTTP requests to different handlers based on pattern matching on the request path. It also enables you to extract values from the path and use them as parameters in the request.

This is particularly useful when developing REST-style web applications.

To do this you simply create an instance of org.vertx.java.core.http.RouteMatcher and use it as handler in an HTTP server. See the chapter on HTTP servers for more information on setting HTTP handlers. Here's an example:

HttpServer server = vertx.createHttpServer();

RouteMatcher routeMatcher = new RouteMatcher();

server.requestHandler(routeMatcher).listen(8080, "localhost");

Specifying matches.


You can then add different matches to the route matcher. For example, to send all GET requests with path /animals/dogs to one handler and all GET requests with path /animals/cats to another handler you would do:

HttpServer server = vertx.createHttpServer();

RouteMatcher routeMatcher = new RouteMatcher();

routeMatcher.get("/animals/dogs", new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest req) {
        req.response().end("You requested dogs");
    }
});
routeMatcher.get("/animals/cats", new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest req) {
        req.response().end("You requested cats");
    }
});

server.requestHandler(routeMatcher).listen(8080, "localhost");

Corresponding methods exist for each HTTP method - get, post, put, delete, head, options, trace, connect and patch.

There's also an all method which applies the match to any HTTP request method.

The handler specified to the method is just a normal HTTP server request handler, the same as you would supply to the requestHandler method of the HTTP server.

You can provide as many matches as you like and they are evaluated in the order you added them, the first matching one will receive the request.

A request is sent to at most one handler.

Extracting parameters from the path


If you want to extract parameters from the path, you can do this too, by using the : (colon) character to denote the name of a parameter. For example:

HttpServer server = vertx.createHttpServer();

RouteMatcher routeMatcher = new RouteMatcher();

routeMatcher.put("/:blogname/:post", new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest req) {
        String blogName = req.params().get("blogname");
        String post = req.params().get("post");
        req.response().end("blogname is " + blogName + ", post is " + post);
    }
});

server.requestHandler(routeMatcher).listen(8080, "localhost");

Any params extracted by pattern matching are added to the map of request parameters.

In the above example, a PUT request to /myblog/post1 would result in the variable blogName getting the value myblog and the variable post getting the value post1.

Valid parameter names must start with a letter of the alphabet and be followed by any letters of the alphabet or digits or the underscore character.

Extracting params using Regular Expressions


Regular Expressions can be used to extract more complex matches. In this case capture groups are used to capture any parameters.

Since the capture groups are not named they are added to the request with names param0, param1, param2, etc.

Corresponding methods exist for each HTTP method - getWithRegEx, postWithRegEx, putWithRegEx, deleteWithRegEx, headWithRegEx, optionsWithRegEx, traceWithRegEx, connectWithRegEx and patchWithRegEx.

There's also an allWithRegEx method which applies the match to any HTTP request method.

For example:

HttpServer server = vertx.createHttpServer();

RouteMatcher routeMatcher = new RouteMatcher();

routeMatcher.allWithRegEx("\\/([^\\/]+)\\/([^\\/]+)", new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest req) {
        String first = req.params().get("param0");
        String second = req.params().get("param1");
        req.response.end("first is " + first + " and second is " + second);
    }
});

server.requestHandler(routeMatcher).listen(8080, "localhost");

Run the above and point your browser at http://localhost:8080/animals/cats.

Handling requests where nothing matches


You can use the noMatch method to specify a handler that will be called if nothing matches. If you don't specify a no match handler and nothing matches, a 404 will be returned.

routeMatcher.noMatch(new Handler<HttpServerRequest>() {
    public void handle(HttpServerRequest req) {
        req.response().end("Nothing matched");'
    }
});

WebSockets


WebSockets are a web technology that allows a full duplex socket-like connection between HTTP servers and HTTP clients (typically browsers).

WebSockets on the server


To use WebSockets on the server you create an HTTP server as normal, but instead of setting a requestHandler you set a websocketHandler on the server.

HttpServer server = vertx.createHttpServer();

server.websocketHandler(new Handler<ServerWebSocket>() {
    public void handle(ServerWebSocket ws) {
        // A WebSocket has connected!
    }
}).listen(8080, "localhost");

Reading from and Writing to WebSockets


The websocket instance passed into the handler implements both ReadStream and WriteStream, so you can read and write data to it in the normal ways. I.e by setting a dataHandler and calling the write method.

See the chapter on streams and pumps for more information.

For example, to echo all data received on a WebSocket:

HttpServer server = vertx.createHttpServer();

server.websocketHandler(new Handler<ServerWebSocket>() {
    public void handle(ServerWebSocket ws) {
        Pump.createPump(ws, ws).start();
    }
}).listen(8080, "localhost");

The websocket instance also has method writeBinaryFrame for writing binary data. This has the same effect as calling write.

Another method writeTextFrame also exists for writing text data. This is equivalent to calling

websocket.write(new Buffer("some-string"));

Rejecting WebSockets


Sometimes you may only want to accept WebSockets which connect at a specific path.

To check the path, you can query the path() method of the websocket. You can then call the reject() method to reject the websocket.

HttpServer server = vertx.createHttpServer();

server.websocketHandler(new Handler<ServerWebSocket>() {
    public void handle(ServerWebSocket ws) {
        if (ws.path().equals("/services/echo")) {
            Pump.createPump(ws, ws).start();
        } else {
            ws.reject();
        }
    }
}).listen(8080, "localhost");

Headers on the websocket


You can use the headers() method to retrieve the headers passed in the Http Request from the client that caused the upgrade to websockets.

WebSockets on the HTTP client


To use WebSockets from the HTTP client, you create the HTTP client as normal, then call the connectWebsocket function, passing in the URI that you wish to connect to at the server, and a handler.

The handler will then get called if the WebSocket successfully connects. If the WebSocket does not connect - perhaps the server rejects it - then any exception handler on the HTTP client will be called.

Here's an example of WebSocket connection;

HttpClient client = vertx.createHttpClient().setHost("foo.com");

client.connectWebsocket("/some-uri", new Handler<WebSocket>() {
    public void handle(WebSocket ws) {
        // Connected!
    }
});

Note that the host (and port) is set on the HttpClient instance, and the uri passed in the connect is typically a relative URI.

Again, the client side WebSocket implements ReadStream and WriteStream, so you can read and write to it in the same way as any other stream object.

WebSockets in the browser


To use WebSockets from a compliant browser, you use the standard WebSocket API. Here's some example client side JavaScript which uses a WebSocket.

<script>

    var socket = new WebSocket("ws://foo.com/services/echo");

    socket.onmessage = function(event) {
        alert("Received data from websocket: " + event.data);
    }

    socket.onopen = function(event) {
        alert("Web Socket opened");
        socket.send("Hello World");
    };

    socket.onclose = function(event) {
        alert("Web Socket closed");
    };

</script>

For more information see the WebSocket API documentation

SockJS


WebSockets are a new technology, and many users are still using browsers that do not support them, or which support older, pre-final, versions.

Moreover, WebSockets do not work well with many corporate proxies. This means that's it's not possible to guarantee a WebSockets connection is going to succeed for every user.

Enter SockJS.

SockJS is a client side JavaScript library and protocol which provides a simple WebSocket-like interface to the client side JavaScript developer irrespective of whether the actual browser or network will allow real WebSockets.

It does this by supporting various different transports between browser and server, and choosing one at runtime according to browser and network capabilities. All this is transparent to you - you are simply presented with the WebSocket-like interface which just works.

Please see the SockJS website for more information.

SockJS Server


Vert.x provides a complete server side SockJS implementation.

This enables Vert.x to be used for modern, so-called real-time (this is the modern meaning of real-time, not to be confused by the more formal pre-existing definitions of soft and hard real-time systems) web applications that push data to and from rich client-side JavaScript applications, without having to worry about the details of the transport.

To create a SockJS server you simply create a HTTP server as normal and then call the createSockJSServer method of your vertx instance passing in the Http server:

HttpServer httpServer = vertx.createHttpServer();

SockJSServer sockJSServer = vertx.createSockJSServer(httpServer);

Each SockJS server can host multiple applications.

Each application is defined by some configuration, and provides a handler which gets called when incoming SockJS connections arrive at the server.

For example, to create a SockJS echo application:

HttpServer httpServer = vertx.createHttpServer();

SockJSServer sockJSServer = vertx.createSockJSServer(httpServer);

JsonObject config = new JsonObject().putString("prefix", "/echo");

sockJSServer.installApp(config, new Handler<SockJSSocket>() {
    public void handle(SockJSSocket sock) {
        Pump.createPump(sock, sock).start();
    }
});

httpServer.listen(8080);

The configuration is an instance of org.vertx.java.core.json.JsonObject, which takes the following fields:

  • prefix: A url prefix for the application. All http requests whose paths begins with selected prefix will be handled by the application. This property is mandatory.
  • insert_JSESSIONID: Some hosting providers enable sticky sessions only to requests that have JSESSIONID cookie set. This setting controls if the server should set this cookie to a dummy value. By default setting JSESSIONID cookie is enabled. More sophisticated beaviour can be achieved by supplying a function.
  • session_timeout: The server sends a close event when a client receiving connection have not been seen for a while. This delay is configured by this setting. By default the close event will be emitted when a receiving connection wasn't seen for 5 seconds.
  • heartbeat_period: In order to keep proxies and load balancers from closing long running http requests we need to pretend that the connecion is active and send a heartbeat packet once in a while. This setting controlls how often this is done. By default a heartbeat packet is sent every 5 seconds.
  • max_bytes_streaming: Most streaming transports save responses on the client side and don't free memory used by delivered messages. Such transports need to be garbage-collected once in a while. max_bytes_streaming sets a minimum number of bytes that can be send over a single http streaming request before it will be closed. After that client needs to open new request. Setting this value to one effectively disables streaming and will make streaming transports to behave like polling transports. The default value is 128K.
  • library_url: Transports which don't support cross-domain communication natively ('eventsource' to name one) use an iframe trick. A simple page is served from the SockJS server (using its foreign domain) and is placed in an invisible iframe. Code run from this iframe doesn't need to worry about cross-domain issues, as it's being run from domain local to the SockJS server. This iframe also does need to load SockJS javascript client library, and this option lets you specify its url (if you're unsure, point it to the latest minified SockJS client release, this is the default). The default value is http://cdn.sockjs.org/sockjs-0.3.4.min.js

Reading and writing data from a SockJS server


The SockJSSocket object passed into the SockJS handler implements ReadStream and WriteStream much like NetSocket or WebSocket. You can therefore use the standard API for reading and writing to the SockJS socket or using it in pumps.

See the chapter on Streams and Pumps for more information.

SockJS client


For full information on using the SockJS client library please see the SockJS website. A simple example:

<script>
   var sock = new SockJS('http://mydomain.com/my_prefix');

   sock.onopen = function() {
       console.log('open');
   };

   sock.onmessage = function(e) {
       console.log('message', e.data);
   };

   sock.onclose = function() {
       console.log('close');
   };
</script>

As you can see the API is very similar to the WebSockets API.

SockJS - EventBus Bridge


Setting up the Bridge


By connecting up SockJS and the Vert.x event bus we create a distributed event bus which not only spans multiple Vert.x instances on the server side, but can also include client side JavaScript running in browsers.

We can therefore create a huge distributed bus encompassing many browsers and servers. The browsers don't have to be connected to the same server as long as the servers are connected.

On the server side we have already discussed the event bus API.

We also provide a client side JavaScript library called vertxbus.js which provides the same event bus API, but on the client side.

This library internally uses SockJS to send and receive data to a SockJS Vert.x server called the SockJS bridge. It's the bridge's responsibility to bridge data between SockJS sockets and the event bus on the server side.

Creating a Sock JS bridge is simple. You just call the bridge method on the SockJS server.

You will also need to secure the bridge (see below).

The following example bridges the event bus to client side JavaScript:

HttpServer server = vertx.createHttpServer();

JsonObject config = new JsonObject().putString("prefix", "/eventbus");

JsonArray noPermitted = new JsonArray();
noPermitted.add(new JsonObject());

vertx.createSockJSServer(server).bridge(config, noPermitted, noPermitted);

server.listen(8080);

To let all messages through you can specify two JSON array with a single empty JSON object which will match all messages.

Be very careful!

Using the Event Bus from client side JavaScript


Once you've set up a bridge, you can use the event bus from the client side as follows:

In your web page, you need to load the script vertxbus.js, then you can access the Vert.x event bus API. Here's a rough idea of how to use it. For a full working examples, please consult the vert.x examples.

<script src="http://cdn.sockjs.org/sockjs-0.3.4.min.js"></script>
<script src='vertxbus.js'></script>

<script>

    var eb = new vertx.EventBus('http://localhost:8080/eventbus');

    eb.onopen = function() {

      eb.registerHandler('some-address', function(message) {

        console.log('received a message: ' + JSON.stringify(message);

      });

      eb.send('some-address', {name: 'tim', age: 587});

    }

</script>

You can find vertxbus.js in the client directory of the Vert.x distribution.

The first thing the example does is to create a instance of the event bus

var eb = new vertx.EventBus('http://localhost:8080/eventbus');

The parameter to the constructor is the URI where to connect to the event bus. Since we create our bridge with the prefix eventbus we will connect there.

You can't actually do anything with the bridge until it is opened. When it is open the onopen handler will be called.

The client side event bus API for registering and unregistering handlers and for sending messages is the same as the server side one. Please consult the chapter on the event bus for full information.

There is one more thing to do before getting this working, please read the following section....

Securing the Bridge


If you started a bridge like in the above example without securing it, and attempted to send messages through it you'd find that the messages mysteriously disappeared. What happened to them?

For most applications you probably don't want client side JavaScript being able to send just any message to any verticle on the server side or to all other browsers.

For example, you may have a persistor verticle on the event bus which allows data to be accessed or deleted. We don't want badly behaved or malicious clients being able to delete all the data in your database! Also, we don't necessarily want any client to be able to listen in on any topic.

To deal with this, a SockJS bridge will, by default refuse to let through any messages. It's up to you to tell the bridge what messages are ok for it to pass through. (There is an exception for reply messages which are always allowed through).

In other words the bridge acts like a kind of firewall which has a default deny-all policy.

Configuring the bridge to tell it what messages it should pass through is easy. You pass in two Json arrays that represent matches, as arguments to bridge.

The first array is the inbound list and represents the messages that you want to allow through from the client to the server. The second array is the outbound list and represents the messages that you want to allow through from the server to the client.

Each match can have up to three fields:

  1. address: This represents the exact address the message is being sent to. If you want to filter messages based on an exact address you use this field.
  2. address_re: This is a regular expression that will be matched against the address. If you want to filter messages based on a regular expression you use this field. If the address field is specified this field will be ignored.
  3. match: This allows you to filter messages based on their structure. Any fields in the match must exist in the message with the same values for them to be passed. This currently only works with JSON messages.

When a message arrives at the bridge, it will look through the available permitted entries.

  • If an address field has been specified then the address must match exactly with the address of the message for it to be considered matched.

  • If an address field has not been specified and an address_re field has been specified then the regular expression in address_re must match with the address of the message for it to be considered matched.

  • If a match field has been specified, then also the structure of the message must match.

Here is an example:

HttpServer server = vertx.createHttpServer();

JsonObject config = new JsonObject().putString("prefix", "/echo");

JsonArray inboundPermitted = new JsonArray();

// Let through any messages sent to 'demo.orderMgr'
JsonObject inboundPermitted1 = new JsonObject().putString("address", "demo.orderMgr");
inboundPermitted.add(inboundPermitted1);

// Allow calls to the address 'demo.persistor' as long as the messages
// have an action field with value 'find' and a collection field with value
// 'albums'
JsonObject inboundPermitted2 = new JsonObject().putString("address", "demo.persistor")
    .putObject("match", new JsonObject().putString("action", "find")
                                        .putString("collection", "albums"));
inboundPermitted.add(inboundPermitted2);

// Allow through any message with a field `wibble` with value `foo`.
JsonObject inboundPermitted3 = new JsonObject().putObject("match", new JsonObject().putString("wibble", "foo"));
inboundPermitted.add(inboundPermitted3);

JsonArray outboundPermitted = new JsonArray();

// Let through any messages coming from address 'ticker.mystock'
JsonObject outboundPermitted1 = new JsonObject().putString("address", "ticker.mystock");
outboundPermitted.add(outboundPermitted1);

// Let through any messages from addresses starting with "news." (e.g. news.europe, news.usa, etc)
JsonObject outboundPermitted2 = new JsonObject().putString("address_re", "news\\..+");
outboundPermitted.add(outboundPermitted2);

vertx.createSockJSBridge(server).bridge(config, inboundPermitted, outboundPermitted);

server.listen(8080);

Messages that require authorisation


The bridge can also refuse to let certain messages through if the user is not authorised.

To enable this you need to make sure an instance of the vertx.auth-mgr module is available on the event bus. (Please see the modules manual for a full description of modules).

To tell the bridge that certain messages require authorisation before being passed, you add the field requires_auth with the value of true in the match. The default value is false. For example, the following match:

{
  address : 'demo.persistor',
  match : {
    action : 'find',
    collection : 'albums'
  },
  requires_auth: true
}

This tells the bridge that any messages to save orders in the orders collection, will only be passed if the user is successful authenticated (i.e. logged in ok) first.

File System


Vert.x lets you manipulate files on the file system. File system operations are asynchronous and take a handler function as the last argument. This function will be called when the operation is complete, or an error has occurred.

The argument passed into the handler is an instance of org.vertx.java.core.AsyncResult.

Synchronous forms


For convenience, we also provide synchronous forms of most operations. It's highly recommended the asynchronous forms are always used for real applications.

The synchronous form does not take a handler as an argument and returns its results directly. The name of the synchronous function is the same as the name as the asynchronous form with Sync appended.

copy


Copies a file.

This function can be called in two different ways:

  • copy(source, destination, handler)

Non recursive file copy. source is the source file name. destination is the destination file name.

Here's an example:

vertx.fileSystem().copy("foo.dat", "bar.dat", new AsyncResultHandler<Void>() {
    public void handle(AsyncResult ar) {
        if (ar.succeeded()) {
            log.info("Copy was successful");
        } else {
            log.error("Failed to copy", ar.cause());
        }
    }
});
  • copy(source, destination, recursive, handler)

Recursive copy. source is the source file name. destination is the destination file name. recursive is a boolean flag - if true and source is a directory, then a recursive copy of the directory and all its contents will be attempted.

move


Moves a file.

move(source, destination, handler)

source is the source file name. destination is the destination file name.

truncate


Truncates a file.

truncate(file, len, handler)

file is the file name of the file to truncate. len is the length in bytes to truncate it to.

chmod


Changes permissions on a file or directory.

This function can be called in two different ways:

  • chmod(file, perms, handler).

Change permissions on a file.

file is the file name. perms is a Unix style permissions string made up of 9 characters. The first three are the owner's permissions. The second three are the group's permissions and the third three are others permissions. In each group of three if the first character is r then it represents a read permission. If the second character is w it represents write permission. If the third character is x it represents execute permission. If the entity does not have the permission the letter is replaced with -. Some examples:

rwxr-xr-x
r--r--r--
  • chmod(file, perms, dirPerms, handler).

Recursively change permissionson a directory. file is the directory name. perms is a Unix style permissions to apply recursively to any files in the directory. dirPerms is a Unix style permissions string to apply to the directory and any other child directories recursively.

props


Retrieve properties of a file.

props(file, handler)

file is the file name. The props are returned in the handler. The results is an object with the following methods:

  • creationTime(): Time of file creation.
  • lastAccessTime(): Time of last file access.
  • lastModifiedTime(): Time file was last modified.
  • isDirectory(): This will have the value true if the file is a directory.
  • isRegularFile(): This will have the value true if the file is a regular file (not symlink or directory).
  • isSymbolicLink(): This will have the value true if the file is a symbolic link.
  • isOther(): This will have the value true if the file is another type.

Here's an example:

vertx.fileSystem().props("foo.dat", "bar.dat", new AsyncResultHandler<FileProps>() {
    public void handle(AsyncResult<FileProps> ar) {
        if (ar.succeeded()) {
            log.info("File props are:");
            log.info("Last accessed: " + ar.result().lastAccessTime());
            // etc
        } else {
            log.error("Failed to get props", ar.cause());
        }
    }
});

lprops


Retrieve properties of a link. This is like props but should be used when you want to retrieve properties of a link itself without following it.

It takes the same arguments and provides the same results as props.


Create a hard link.

link(link, existing, handler)

link is the name of the link. existing is the exsting file (i.e. where to point the link at).


Create a symbolic link.

symlink(link, existing, handler)

link is the name of the symlink. existing is the exsting file (i.e. where to point the symlink at).


Unlink (delete) a link.

unlink(link, handler)

link is the name of the link to unlink.


Reads a symbolic link. I.e returns the path representing the file that the symbolic link specified by link points to.

readSymLink(link, handler)

link is the name of the link to read. An usage example would be:

vertx.fileSystem().readSymLink("somelink", new AsyncResultHandler<String>() {
    public void handle(AsyncResult<String> ar) {
        if (ar.succeeded()) {
            log.info("Link points at  " + ar.result());
        } else {
            log.error("Failed to read", ar.cause());
        }
    }
});

delete


Deletes a file or recursively deletes a directory.

This function can be called in two ways:

  • delete(file, handler)

Deletes a file. file is the file name.

  • delete(file, recursive, handler)

If recursive is true, it deletes a directory with name file, recursively. Otherwise it just deletes a file.

mkdir


Creates a directory.

This function can be called in three ways:

  • mkdir(dirname, handler)

Makes a new empty directory with name dirname, and default permissions `

  • mkdir(dirname, createParents, handler)

If createParents is true, this creates a new directory and creates any of its parents too. Here's an example

vertx.fileSystem().mkdir("a/b/c", true, new AsyncResultHandler<Void>() {
    public void handle(AsyncResult ar) {
        if (ar.suceeded()) {
            log.info("Directory created ok");
        } else {
            log.error("Failed to mkdir", ar.cause());
        }
    }
});
  • mkdir(dirname, createParents, perms, handler)

Like mkdir(dirname, createParents, handler), but also allows permissions for the newly created director(ies) to be specified. perms is a Unix style permissions string as explained earlier.

readDir


Reads a directory. I.e. lists the contents of the directory.

This function can be called in two ways:

  • readDir(dirName)

Lists the contents of a directory

  • readDir(dirName, filter)

List only the contents of a directory which match the filter. Here's an example which only lists files with an extension txt in a directory.

vertx.fileSystem().readDir("mydirectory", ".*\\.txt", new AsyncResultHandler<String[]>() {
    public void handle(AsyncResult<String[]> ar) {
        if (ar.succeeded() {
            log.info("Directory contains these .txt files");
            for (int i = 0; i < ar.result().length; i++) {
              log.info(ar.result()[i]);
            }
        } else {
            log.error("Failed to read", ar.cause());
        }
    }
});

The filter is a regular expression.

readFile


Read the entire contents of a file in one go. Be careful if using this with large files since the entire file will be stored in memory at once.

readFile(file). Where file is the file name of the file to read.

The body of the file will be returned as an instance of org.vertx.java.core.buffer.Buffer in the handler.

Here is an example:

vertx.fileSystem().readFile("myfile.dat", new AsyncResultHandler<Buffer>() {
    public void handle(AsyncResult<Buffer> ar) {
        if (ar.succeeded()) {
            log.info("File contains: " + ar.result().length() + " bytes");
        } else {
            log.error("Failed to read", ar.cause());
        }
    }
});

writeFile


Writes an entire Buffer or a string into a new file on disk.

writeFile(file, data, handler) Where file is the file name. data is a Buffer or string.

createFile


Creates a new empty file.

createFile(file, handler). Where file is the file name.

exists


Checks if a file exists.

exists(file, handler). Where file is the file name.

The result is returned in the handler.

vertx.fileSystem().exists("some-file.txt", new AsyncResultHandler<Boolean>() {
    public void handle(AsyncResult<Boolean> ar) {
        if (ar.succeeded()) {
            log.info("File " + (ar.result() ? "exists" : "does not exist"));
        } else {
            log.error("Failed to check existence", ar.cause());
        }
    }
});

fsProps


Get properties for the file system.

fsProps(file, handler). Where file is any file on the file system.

The result is returned in the handler. The result object is an instance of org.vertx.java.core.file.FileSystemProps has the following methods:

  • totalSpace(): Total space on the file system in bytes.
  • unallocatedSpace(): Unallocated space on the file system in bytes.
  • usableSpace(): Usable space on the file system in bytes.

Here is an example:

vertx.fileSystem().fsProps("mydir", new AsyncResultHandler<FileSystemProps>() {
    public void handle(AsyncResult<FileSystemProps> ar) {
        if (ar.succeeded()) {
            log.info("total space: " + ar.result().totalSpace());
            // etc
        } else {
            log.error("Failed to check existence", ar.cause());
        }
    }
});

open


Opens an asynchronous file for reading \ writing.

This function can be called in four different ways:

  • open(file, handler)

Opens a file for reading and writing. file is the file name. It creates it if it does not already exist.

  • open(file, perms, handler)

Opens a file for reading and writing. file is the file name. It creates it if it does not already exist and assigns it the permissions as specified by perms.

  • open(file, perms, createNew, handler)

Opens a file for reading and writing. file is the file name. It createNew is true it creates it if it does not already exist.

  • open(file, perms, read, write, createNew, handler)

Opens a file. file is the file name. If read is true it is opened for reading. If write is true it is opened for writing. It createNew is true it creates it if it does not already exist.

  • open(file, perms, read, write, createNew, flush, handler)

Opens a file. file is the file name. If read is true it is opened for reading. If write is true it is opened for writing. It createNew is true it creates it if it does not already exist. If flush is true all writes are immediately flushed through the OS cache (default value of flush is false).

When the file is opened, an instance of org.vertx.java.core.file.AsyncFile is passed into the result handler:

vertx.fileSystem().open("some-file.dat", new AsyncResultHandler<AsyncFile>() {
    public void handle(AsyncResult<AsyncFile> ar) {
        if (ar.succeeded()) {
            log.info("File opened ok!");
            // etc
        } else {
            log.error("Failed to open file", ar.cause());
        }
    }
});

AsyncFile


Instances of org.vertx.java.core.file.AsyncFile are returned from calls to open and you use them to read from and write to files asynchronously. They allow asynchronous random file access.

AsyncFile implementsReadStream and WriteStream so you can pump files to and from other stream objects such as net sockets, http requests and responses, and WebSockets.

They also allow you to read and write directly to them.

Random access writes


To use an AsyncFile for random access writing you use the write method.

write(buffer, position, handler).

The parameters to the method are:

  • buffer: the buffer to write.
  • position: an integer position in the file where to write the buffer. If the position is greater or equal to the size of the file, the file will be enlarged to accomodate the offset.

Here is an example of random access writes:

vertx.fileSystem().open("some-file.dat", new AsyncResultHandler<AsyncFile>() {
    public void handle(AsyncResult<AsyncFile> ar) {
        if (ar.succeeded()) {
            AsyncFile asyncFile = ar.result();
            // File open, write a buffer 5 times into a file
            Buffer buff = new Buffer("foo");
            for (int i = 0; i < 5; i++) {
                asyncFile.write(buff, buff.length() * i, new AsyncResultHandler<Void>() {
                    public void handle(AsyncResult ar) {
                        if (ar.succeeded()) {
                            log.info("Written ok!");
                            // etc
                        } else {
                            log.error("Failed to write", ar.cause());
                        }
                    }
                });
            }
        } else {
            log.error("Failed to open file", ar.cause());
        }
    }
});

Random access reads


To use an AsyncFile for random access reads you use the read method.

read(buffer, offset, position, length, handler).

The parameters to the method are:

  • buffer: the buffer into which the data will be read.
  • offset: an integer offset into the buffer where the read data will be placed.
  • position: the position in the file where to read data from.
  • length: the number of bytes of data to read

Here's an example of random access reads:

vertx.fileSystem().open("some-file.dat", new AsyncResultHandler<AsyncFile>() {
    public void handle(AsyncResult<AsyncFile> ar) {
        if (ar.succeeded()) {
            AsyncFile asyncFile = ar.result();
            Buffer buff = new Buffer(1000);
            for (int i = 0; i < 10; i++) {
                asyncFile.read(buff, i * 100, i * 100, 100, new AsyncResultHandler<Buffer>() {
                    public void handle(AsyncResult<Buffer> ar) {
                        if (ar.succeeded()) {
                            log.info("Read ok!");
                            // etc
                        } else {
                            log.error("Failed to write", ar.cause());
                        }
                    }
                });
            }
        } else {
            log.error("Failed to open file", ar.cause());
        }
    }
});

If you attempt to read past the end of file, the read will not fail but it will simply read zero bytes.

Flushing data to underlying storage.


If the AsyncFile was not opened with flush = true, then you can manually flush any writes from the OS cache by calling the flush() method.

This method can also be called with an handler which will be called when the flush is complete.

Using AsyncFile as ReadStream and WriteStream


AsyncFile implements ReadStream and WriteStream. You can then use them with a pump to pump data to and from other read and write streams.

Here's an example of pumping data from a file on a client to a HTTP request:

final HttpClient client = vertx.createHttpClient.setHost("foo.com");

vertx.fileSystem().open("some-file.dat", new AsyncResultHandler<AsyncFile>() {
    public void handle(AsyncResult<AsyncFile> ar) {
        if (ar.succeeded()) {
            final HttpClientRequest request = client.put("/uploads", new Handler<HttpClientResponse>() {
                public void handle(HttpClientResponse resp) {
                    log.info("Received response: " + resp.statusCode());
                }
            });
            AsyncFile asyncFile = ar.result();
            request.setChunked(true);
            Pump.createPump(asyncFile, request).start();
            asyncFile.endHandler(new VoidHandler() {
                public void handle() {
                    // File sent, end HTTP requuest
                    request.end();
                }
            });
        } else {
            log.error("Failed to open file", ar.cause());
        }
    }
});

Closing an AsyncFile


To close an AsyncFile call the close() method. Closing is asynchronous and if you want to be notified when the close has been completed you can specify a handler function as an argument.

DNS Client


Often you will find yourself in situations where you need to obtain DNS informations in an asynchronous fashion. Unfortunally this is not possible with the API that is shipped with Java itself. Because of this Vert.x offers it's own API for DNS resolution which is fully asynchronous.

To obtain a DnsClient instance you will create a new via the Vertx instance.

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53), new InetSocketAddress("10.0.0.2", 53));

Be aware that you can pass in a varargs of InetSocketAddress arguments to specifiy more then one DNS Server to try to query for DNS resolution. The DNS Servers will be queried in the same order as specified here. Where the next will be used once the first produce an error while be used.

lookup


Try to lookup the A (ipv4) or AAAA (ipv6) record for a given name. The first which is returned will be used, so it behaves the same way as you may be used from when using "nslookup" on your operation system.

To lookup the A / AAAA record for "vertx.io" you would typically use it like:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.lookup("vertx.io", new AsyncResultHandler<InetAddress>() {
    public void handle(AsyncResult<InetAddress> ar) {
        if (ar.succeeded()) {
            System.out.println(ar.result());
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

Be aware that it either would use an Inet4Address or Inet6Address in the AsyncResult depending on if an A or AAAA record was resolved.

lookup4


Try to lookup the A (ipv4) record for a given name. The first which is returned will be used, so it behaves the same way as you may be used from when using "nslookup" on your operation system.

To lookup the A record for "vertx.io" you would typically use it like:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.lookup4("vertx.io", new AsyncResultHandler<Inet4Address>() {
    public void handle(AsyncResult<Inet4Address> ar) {
        if (ar.succeeded()) {
            System.out.println(ar.result());
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

As it only resolves A records and so is ipv4 only it will use Inet4Address as result.

lookup6


Try to lookup the AAAA (ipv5) record for a given name. The first which is returned will be used, so it behaves the same way as you may be used from when using "nslookup" on your operation system.

To lookup the A record for "vertx.io" you would typically use it like:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.lookup6("vertx.io", new AsyncResultHandler<Inet6Address>() {
    public void handle(AsyncResult<Inet6Address> ar) {
        if (ar.succeeded()) {
            System.out.println(ar.result());
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

As it only resolves AAAA records and so is ipv6 only it will use Inet6Address as result.

resolveA


Try to resolve all A (ipv4) records for a given name. This is quite similar to using "dig" on unix like operation systems.

To lookup all the A records for "vertx.io" you would typically do:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveA("vertx.io", new AsyncResultHandler<List<Inet4Address>>() {
    public void handle(AsyncResult<List<Inet4Address>> ar) {
        if (ar.succeeded()) {
            List<Inet4Address> records = ar.result());
            for (Inet4Address record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

As it only resolves A records and so is ipv4 only it will use Inet4Address as result.

resolveAAAA


Try to resolve all AAAA (ipv6) records for a given name. This is quite similar to using "dig" on unix like operation systems.

To lookup all the AAAAA records for "vertx.io" you would typically do:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveAAAA("vertx.io", new AsyncResultHandler<List<Inet6Address>>() {
    public void handle(AsyncResult<List<Inet6Address>> ar) {
        if (ar.succeeded()) {
            List<Inet6Address> records = ar.result());
            for (Inet6Address record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

As it only resolves AAAA records and so is ipv6 only it will use Inet6Address as result.

resolveCNAME


Try to resolve all CNAME records for a given name. This is quite similar to using "dig" on unix like operation systems.

To lookup all the CNAME records for "vertx.io" you would typically do:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveCNAME("vertx.io", new AsyncResultHandler<List<String>>() {
    public void handle(AsyncResult<List<String>> ar) {
        if (ar.succeeded()) {
            List<String> records = ar.result());
            for (String record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

resolveMX


Try to resolve all MX records for a given name. The MX records are used to define which Mail-Server accepts emails for a given domain.

To lookup all the MX records for "vertx.io" you would typically do:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveMX("vertx.io", new AsyncResultHandler<List<MxRecord>>() {
    public void handle(AsyncResult<List<MxRecord>> ar) {
        if (ar.succeeded()) {
            List<MxRecord> records = ar.result());
            for (MxRecord record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

Be aware that the List will contain the MxRecords sorted by the priority of them, which means MxRecords with smaller priority coming first in the List.

The MxRecord allows you to access the priority and the name of the MX record by offer methods for it like:

MxRecord record = ...
record.priority();
record.name();

resolveTXT


Try to resolve all TXT records for a given name. TXT records are often used to define extra informations for a domain.

To resolve all the TXT records for "vertx.io" you could use something along these lines:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveTXT("vertx.io", new AsyncResultHandler<List<String>>() {
    public void handle(AsyncResult<List<String>> ar) {
        if (ar.succeeded()) {
            List<String> records = ar.result());
            for (String record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

resolveNS


Try to resolve all NS records for a given name. The NS records specify which DNS Server hosts the DNS informations for a given domain.

To resolve all the NS records for "vertx.io" you could use something along these lines:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveNS("vertx.io", new AsyncResultHandler<List<String>>() {
    public void handle(AsyncResult<List<String>> ar) {
        if (ar.succeeded()) {
            List<String> records = ar.result());
            for (String record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

resolveSRV


Try to resolve all SRV records for a given name. The SRV records are used to define extra informations like port and hostname of services. Some protocols need this extra informations.

To lookup all the SRV records for "vertx.io" you would typically do:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveMX("vertx.io", new AsyncResultHandler<List<SrvRecord>>() {
    public void handle(AsyncResult<List<SrvRecord>> ar) {
        if (ar.succeeded()) {
            List<SrvRecord> records = ar.result());
            for (SrvRecord record: records) {
                System.out.println(record);
            }
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

Be aware that the List will contain the SrvRecords sorted by the priority of them, which means SrvRecords with smaller priority coming first in the List.

The SrvRecord allows you to access all informations contained in the SRV record itself:

SrvRecord record = ...
record.priority();
record.name();
record.priority();
record.weight();
record.port();
record.protocol();
record.service();
record.target();

Please refer to the API docs for the exact details.

resolvePTR


Try to resolve the PTR record for a given name. The PTR record maps an ipaddress to a name.

To resolve the PTR record for the ipaddress 10.0.0.1 you would use the PTR notion of "1.0.0.10.in-addr.arpa"

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.resolveTXT("1.0.0.10.in-addr.arpa", new AsyncResultHandler<String>() {
    public void handle(AsyncResult<String> ar) {
        if (ar.succeeded()) {
            String record = ar.result());
            System.out.println(record);
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

reverseLookup


Try to do a reverse lookup for an ipaddress. This is basically the same as resolve a PTR record, but allows you to just pass in the ipaddress and not a valid PTR query string.

To do a reverse lookup for the ipaddress 10.0.0.1 do something similar like this:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.reverseLookup("10.0.0.1", new AsyncResultHandler<String>() {
    public void handle(AsyncResult<String> ar) {
        if (ar.succeeded()) {
            String record = ar.result());
            System.out.println(record);
        } else {
            log.error("Failed to resolve entry", ar.cause());
        }
    }
});

Error handling


As you saw in previous sections the DnsClient allows you to pass in a Handler which will be notified with an AsyncResult once the query was complete. In case of an error it will be notified with a DnsException which will hole a DnsResponseCode that indicate why the resolution failed. This DnsResponseCode can be used to inspect the cause in more detail.

Possible DnsResponseCodes are:

NOERROR


No record was found for a given query

FORMERROR


Format error

SERVFAIL


Server failure

NXDOMAIN


Name error

NOTIMPL


Not implemented by DNS Server

REFUSED


DNS Server refused the query

YXDOMAIN


Domain name should not exist

YXRRSET


Resource record should not exist

NXRRSET


RRSET does not exist

NOTZONE


Name not in zone

BADVER


Bad extension mechanism for version

BADSIG


Bad signature

BADKEY


Bad key

BADTIME


Bad timestamp

All of those errors are "generated" by the DNS Server itself.

You can obtain the DnsResponseCode from the DnsException like:

DnsClient client = vertx.createDnsClient(new InetSocketAddress("10.0.0.1", 53));
client.lookup("nonexisting.vert.xio", new AsyncResultHandler<InetAddress>() {
    public void handle(AsyncResult<InetAddress> ar) {
        if (ar.succeeded()) {
            InetAddress record = ar.result());
            System.out.println(record);
        } else {
            Throwable cause = ar.cause();
            if (cause instanceof DnsException) {
                DnsException exception = (DnsException) cause;
                DnsResponseCode code = exception.code();
                ...
            } else {
                log.error("Failed to resolve entry", ar.cause());
            }
        }
    }
});