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The Reactive MySQL Client is a client for MySQL with a straightforward API focusing on scalability and low overhead.

Features

  • Event driven

  • Lightweight

  • Built-in connection pooling

  • Prepared queries caching

  • Cursor support

  • Row streaming

  • RxJava 1 and RxJava 2

  • Direct memory to object without unnecessary copies

  • Java 8 Date and Time

  • Stored Procedures support

  • TLS/SSL support

  • MySQL utilities commands support

  • Working with MySQL and MariaDB

  • Rich collation and charset support

Usage

To use the Reactive MySQL Client add the following dependency to the dependencies section of your build descriptor:

  • Maven (in your pom.xml):

<dependency>
 <groupId>io.vertx</groupId>
 <artifactId>vertx-lang-kotlin</artifactId>
 <version>3.9.0</version>
</dependency>
  • Gradle (in your build.gradle file):

dependencies {
 compile 'io.vertx:vertx-lang-kotlin:3.9.0'
}

Getting started

Here is the simplest way to connect, query and disconnect

// Connect options
var connectOptions = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret")

// Pool options
var poolOptions = PoolOptions(
  maxSize = 5)

// Create the client pool
var client = MySQLPool.pool(connectOptions, poolOptions)

// A simple query
client.query("SELECT * FROM users WHERE id='julien'").execute({ ar ->
  if (ar.succeeded()) {
    var result = ar.result()
    println("Got ${result.size()} rows ")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }

  // Now close the pool
  client.close()
})

Connecting to MySQL

Most of the time you will use a pool to connect to MySQL:

// Connect options
var connectOptions = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret")

// Pool options
var poolOptions = PoolOptions(
  maxSize = 5)

// Create the pooled client
var client = MySQLPool.pool(connectOptions, poolOptions)

The pooled client uses a connection pool and any operation will borrow a connection from the pool to execute the operation and release it to the pool.

If you are running with Vert.x you can pass it your Vertx instance:

// Connect options
var connectOptions = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret")

// Pool options
var poolOptions = PoolOptions(
  maxSize = 5)
// Create the pooled client
var client = MySQLPool.pool(vertx, connectOptions, poolOptions)

You need to release the pool when you don’t need it anymore:

// Close the pool and all the associated resources
pool.close()

When you need to execute several operations on the same connection, you need to use a client connection.

You can easily get one from the pool:

// Connect options
var connectOptions = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret")

// Pool options
var poolOptions = PoolOptions(
  maxSize = 5)

// Create the pooled client
var client = MySQLPool.pool(vertx, connectOptions, poolOptions)

// Get a connection from the pool
client.getConnection({ ar1 ->

  if (ar1.succeeded()) {

    println("Connected")

    // Obtain our connection
    var conn = ar1.result()

    // All operations execute on the same connection
    conn.query("SELECT * FROM users WHERE id='julien'").execute({ ar2 ->
      if (ar2.succeeded()) {
        conn.query("SELECT * FROM users WHERE id='emad'").execute({ ar3 ->
          // Release the connection to the pool
          conn.close()
        })
      } else {
        // Release the connection to the pool
        conn.close()
      }
    })
  } else {
    println("Could not connect: ${ar1.cause().getMessage()}")
  }
})

Once you are done with the connection you must close it to release it to the pool, so it can be reused.

Configuration

There are several alternatives for you to configure the client.

Data Object

A simple way to configure the client is to specify a MySQLConnectOptions data object.

// Data object
var connectOptions = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret")

// Pool Options
var poolOptions = PoolOptions(
  maxSize = 5)

// Create the pool from the data object
var pool = MySQLPool.pool(vertx, connectOptions, poolOptions)

pool.getConnection({ ar ->
  // Handling your connection
})

collations and character sets

The Reactive MySQL client supports configuring collations or character sets and map them to a correlative java.nio.charset.Charset. For example, you can specify charset for a connection like

var connectOptions = MySQLConnectOptions()

// set connection character set to utf8 instead of the default charset utf8mb4
connectOptions.charset = "utf8"

The Reactive MySQL Client will take utf8mb4 as the default charset. String values like password and error messages are always decoded in UTF-8 charset.

characterEncoding option is used to determine which Java charset will be used to encode String values such as query string and parameter values, the charset is UTF-8 by default and if it’s set to null then the client will use the default Java charset instead.

You can also specify collation for a connection like

var connectOptions = MySQLConnectOptions()

// set connection collation to utf8_general_ci instead of the default collation utf8mb4_general_ci
// setting a collation will override the charset option
connectOptions.charset = "gbk"
connectOptions.collation = "utf8_general_ci"

Note setting a collation on the data object will override the charset and characterEncoding option.

You can execute SQL SHOW COLLATION; or SHOW CHARACTER SET; to get the supported collations and charsets by the server.

More information about MySQL charsets and collations can be found in the MySQL Reference Manual.

connection attributes

You can also configure the connection attributes with the setProperties or addProperty methods. Note setProperties will override the default client properties.

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More information about client connection attributes can be found in the MySQL Reference Manual.

useAffectedRows

You can configure the useAffectedRows option to decide whether to set CLIENT_FOUND_ROWS flag when connecting to the server. If the CLIENT_FOUND_ROWS flag is specified then the affected rows count is the numeric value of rows found rather than affected.

More information about this can be found in the MySQL Reference Manual

connection URI

Apart from configuring with a MySQLConnectOptions data object, We also provide you an alternative way to connect when you want to configure with a connection URI:

// Connection URI
var connectionUri = "mysql://dbuser:[email protected]:3211/mydb"

// Create the pool from the connection URI
var pool = MySQLPool.pool(connectionUri)

// Create the connection from the connection URI
MySQLConnection.connect(vertx, connectionUri, { res ->
  // Handling your connection
})

More information about connection string formats can be found in the MySQL Reference Manual.

Currently the client supports the following parameter key words in connection uri(keys are case-insensitive)

  • host

  • port

  • user

  • password

  • schema

  • socket

  • useAffectedRows

Unresolved directive in index.adoc - include::queries.adoc[]

MySQL LAST_INSERT_ID

You can get the auto incremented value if you insert a record into the table.

client.query("INSERT INTO test(val) VALUES ('v1')").execute({ ar ->
  if (ar.succeeded()) {
    var rows = ar.result()
    var lastInsertId = rows.property(MySQLClient.LAST_INSERTED_ID)
    println("Last inserted id is: ${lastInsertId}")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

More information can be found in How to Get the Unique ID for the Last Inserted Row.

Unresolved directive in index.adoc - include::connections.adoc[]

Unresolved directive in index.adoc - include::transactions.adoc[]

Unresolved directive in index.adoc - include::cursor.adoc[]

MySQL type mapping

Currently the client supports the following MySQL types

  • BOOL,BOOLEAN (java.lang.Byte)

  • TINYINT (java.lang.Byte)

  • TINYINT UNSIGNED(java.lang.Short)

  • SMALLINT (java.lang.Short)

  • SMALLINT UNSIGNED(java.lang.Integer)

  • MEDIUMINT (java.lang.Integer)

  • MEDIUMINT UNSIGNED(java.lang.Integer)

  • INT,INTEGER (java.lang.Integer)

  • INTEGER UNSIGNED(java.lang.Long)

  • BIGINT (java.lang.Long)

  • BIGINT UNSIGNED(io.vertx.sqlclient.data.Numeric)

  • FLOAT (java.lang.Float)

  • FLOAT UNSIGNED(java.lang.Float)

  • DOUBLE (java.lang.Double)

  • DOUBLE UNSIGNED(java.lang.Double)

  • BIT (java.lang.Long)

  • NUMERIC (io.vertx.sqlclient.data.Numeric)

  • NUMERIC UNSIGNED(io.vertx.sqlclient.data.Numeric)

  • DATE (java.time.LocalDate)

  • DATETIME (java.time.LocalDateTime)

  • TIME (java.time.Duration)

  • TIMESTAMP (java.time.LocalDateTime)

  • YEAR (java.lang.Short)

  • CHAR (java.lang.String)

  • VARCHAR (java.lang.String)

  • BINARY (io.vertx.core.buffer.Buffer)

  • VARBINARY (io.vertx.core.buffer.Buffer)

  • TINYBLOB (io.vertx.core.buffer.Buffer)

  • TINYTEXT (java.lang.String)

  • BLOB (io.vertx.core.buffer.Buffer)

  • TEXT (java.lang.String)

  • MEDIUMBLOB (io.vertx.core.buffer.Buffer)

  • MEDIUMTEXT (java.lang.String)

  • LONGBLOB (io.vertx.core.buffer.Buffer)

  • LONGTEXT (java.lang.String)

  • ENUM (java.lang.String)

  • SET (java.lang.String)

  • JSON (io.vertx.core.json.JsonObject, io.vertx.core.json.JsonArray, Number, Boolean, String, io.vertx.sqlclient.Tuple#JSON_NULL)

Tuple decoding uses the above types when storing values

Note: In Java there is no specific representations for unsigned numeric values, so this client will convert an unsigned value to the correlated Java type.

Implicit type conversion

The Reactive MySQL Client supports implicit type conversions when executing a prepared statement. Suppose you have a TIME column in your table, the two examples below will both work here.

client.preparedQuery("SELECT * FROM students WHERE updated_time = ?").execute(Tuple.of(java.time.LocalTime.of(19, 10, 25)), { ar ->
  // handle the results
})
// this will also work with implicit type conversion
client.preparedQuery("SELECT * FROM students WHERE updated_time = ?").execute(Tuple.of("19:10:25"), { ar ->
  // handle the results
})

The MySQL data type for encoding will be inferred from the parameter values and here is the type mapping

Parameter value type encoding MySQL type

null

MYSQL_TYPE_NULL

java.lang.Byte

MYSQL_TYPE_TINY

java.lang.Boolean

MYSQL_TYPE_TINY

java.lang.Short

MYSQL_TYPE_SHORT

java.lang.Integer

MYSQL_TYPE_LONG

java.lang.Long

MYSQL_TYPE_LONGLONG

java.lang.Double

MYSQL_TYPE_DOUBLE

java.lang.Float

MYSQL_TYPE_FLOAT

java.time.LocalDate

MYSQL_TYPE_DATE

java.time.Duration

MYSQL_TYPE_TIME

java.time.LocalTime

MYSQL_TYPE_TIME

io.vertx.core.buffer.Buffer

MYSQL_TYPE_BLOB

java.time.LocalDateTime

MYSQL_TYPE_DATETIME

default

MYSQL_TYPE_STRING

Handling BOOLEAN

In MySQL BOOLEAN and BOOL data types are synonyms for TINYINT(1). A value of zero is considered false, non-zero values are considered true. A BOOLEAN data type value is stored in Row or Tuple as java.lang.Byte type, you can call Row#getValue to retrieve it as a java.lang.Byte value, or you can call Row#getBoolean to retrieve it as java.lang.Boolean value.

client.query("SELECT graduated FROM students WHERE id = 0").execute({ ar ->
  if (ar.succeeded()) {
    var rowSet = ar.result()
    for (row in rowSet) {
      var pos = row.getColumnIndex("graduated")
      var value = row.get(Byte.`class`, pos)
      var graduated = row.getBoolean("graduated")
    }
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

When you want to execute a prepared statement with a param of a BOOLEAN value, you can simply add the java.lang.Boolean value to the params list.

client.preparedQuery("UPDATE students SET graduated = ? WHERE id = 0").execute(Tuple.of(true), { ar ->
  if (ar.succeeded()) {
    println("Updated with the boolean value")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

Handling JSON

MySQL JSON data type is represented by the following Java types:

  • String

  • Number

  • Boolean

  • io.vertx.core.json.JsonObject

  • io.vertx.core.json.JsonArray

  • io.vertx.sqlclient.Tuple#JSON_NULL for representing the JSON null literal

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Handling BIT

The BIT data type is mapped to java.lang.Long type, but Java has no notion of unsigned numeric values, so if you want to insert or update a record with the max value of BIT(64), you can do some tricks setting the parameter to -1L.

Handling TIME

MySQL TIME data type can be used to represent either time of a day or a time interval which ranges from -838:59:59 to 838:59:59. In Reactive MySQL client the TIME data type is mapped to java.time.Duration natively, but you can also retrieve it as a java.time.LocalTime via Row#getLocalTime accessor.

Handling NUMERIC

The Numeric Java type is used to represent the MySQL NUMERIC type.

var numeric = row.get(io.vertx.sqlclient.data.Numeric.`class`, 0)
if (numeric.isNaN()) {
  // Handle NaN
} else {
  var value = numeric.bigDecimalValue()
}

Collector queries

You can use Java collectors with the query API:

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The collector processing must not keep a reference on the Row as there is a single row used for processing the entire set.

The Java Collectors provides many interesting predefined collectors, for example you can create easily create a string directly from the row set:

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MySQL Stored Procedure

You can run stored procedures in queries. The result will be retrieved from the server following the MySQL protocol without any magic here.

client.query("CREATE PROCEDURE multi() BEGIN\n  SELECT 1;\n  SELECT 1;\n  INSERT INTO ins VALUES (1);\n  INSERT INTO ins VALUES (2);\nEND;").execute({ ar1 ->
  if (ar1.succeeded()) {
    // create stored procedure success
    client.query("CALL multi();").execute({ ar2 ->
      if (ar2.succeeded()) {
        // handle the result
        var result1 = ar2.result()
        var row1 = result1.iterator().next()
        println("First result: ${row1.getInteger(0)}")

        var result2 = result1.next()
        var row2 = result2.iterator().next()
        println("Second result: ${row2.getInteger(0)}")

        var result3 = result2.next()
        println("Affected rows: ${result3.rowCount()}")
      } else {
        println("Failure: ${ar2.cause().getMessage()}")
      }
    })
  } else {
    println("Failure: ${ar1.cause().getMessage()}")
  }
})

Note: Prepared statements binding OUT parameters is not supported for now.

MySQL LOCAL INFILE

This client supports for handling the LOCAL INFILE Request, if you want to load data from a local file into the server, you can use query LOAD DATA LOCAL INFILE '<filename>' INTO TABLE <table>;. More information can be found in the MySQL Reference Manual.

Authentication

MySQL 8.0 introduces a new authentication method named caching_sha2_password and it’s the default one to authenticate. In order to connect to the server using this new authentication method, you need either use a secure connection(i.e. enable TLS/SSL) or exchange the encrypted password using an RSA key pair to avoid leaks of password. The RSA key pair is automatically exchanged during the communication, but the server RSA public key may be hacked during the process since it’s transferred on a insecure connection. So if you’re on a insecure connection and want to avoid the risk of exposing the server RSA public key, you can set the server RSA public key like this:

var options1 = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret",
  serverRsaPublicKeyPath = "tls/files/public_key.pem")

var options2 = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret",
  serverRsaPublicKeyValue = Buffer.buffer("-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3yvG5s0qrV7jxVlp0sMj\nxP0a6BuLKCMjb0o88hDsJ3xz7PpHNKazuEAfPxiRFVAV3edqfSiXoQw+lJf4haEG\nHQe12Nfhs+UhcAeTKXRlZP/JNmI+BGoBduQ1rCId9bKYbXn4pvyS/a1ft7SwFkhx\naogCur7iIB0WUWvwkQ0fEj/Mlhw93lLVyx7hcGFq4FOAKFYr3A0xrHP1IdgnD8QZ\n0fUbgGLWWLOossKrbUP5HWko1ghLPIbfmU6o890oj1ZWQewj1Rs9Er92/UDj/JXx\n7ha1P+ZOgPBlV037KDQMS6cUh9vTablEHsMLhDZanymXzzjBkL+wH/b9cdL16LkQ\n5QIDAQAB\n-----END PUBLIC KEY-----\n"))

More information about the caching_sha2_password authentication method can be found in the MySQL Reference Manual.

Using SSL/TLS

To configure the client to use SSL connection, you can configure the MySQLConnectOptions like a Vert.x NetClient. All SSL modes are supported and you are able to configure sslmode. The client is in DISABLED SSL mode by default. ssl parameter is kept as a mere shortcut for setting sslmode. setSsl(true) is equivalent to setSslMode(VERIFY_CA) and setSsl(false) is equivalent to setSslMode(DISABLED).

var options = MySQLConnectOptions(
  port = 3306,
  host = "the-host",
  database = "the-db",
  user = "user",
  password = "secret",
  sslMode = SslMode.VERIFY_CA,
  pemTrustOptions = PemTrustOptions(
    certPaths = listOf("/path/to/cert.pem")))

MySQLConnection.connect(vertx, options, { res ->
  if (res.succeeded()) {
    // Connected with SSL
  } else {
    println("Could not connect ${res.cause()}")
  }
})

More information can be found in the Vert.x documentation.

MySQL utility command

Sometimes you want to use MySQL utility commands and we provide support for this. More information can be found in the MySQL utility commands.

COM_PING

You can use COM_PING command to check if the server is alive. The handler will be notified if the server responds to the PING, otherwise the handler will never be called.

connection.ping({ ar ->
  println("The server has responded to the PING")
})

COM_RESET_CONNECTION

You can reset the session state with COM_RESET_CONNECTION command, this will reset the connection state like: - user variables - temporary tables - prepared statements

connection.resetConnection({ ar ->
  if (ar.succeeded()) {
    println("Connection has been reset now")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

COM_CHANGE_USER

You can change the user of the current connection, this will perform a re-authentication and reset the connection state like COM_RESET_CONNECTION.

var authenticationOptions = MySQLAuthOptions(
  user = "newuser",
  password = "newpassword",
  database = "newdatabase")
connection.changeUser(authenticationOptions, { ar ->
  if (ar.succeeded()) {
    println("User of current connection has been changed.")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

COM_INIT_DB

You can use COM_INIT_DB command to change the default schema of the connection.

connection.specifySchema("newschema", { ar ->
  if (ar.succeeded()) {
    println("Default schema changed to newschema")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

COM_STATISTICS

You can use COM_STATISTICS command to get a human readable string of some internal status variables in MySQL server.

connection.getInternalStatistics({ ar ->
  if (ar.succeeded()) {
    println("Statistics: ${ar.result()}")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

COM_DEBUG

You can use COM_DEBUG command to dump debug info to the MySQL server’s STDOUT.

connection.debug({ ar ->
  if (ar.succeeded()) {
    println("Debug info dumped to server's STDOUT")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

COM_SET_OPTION

You can use COM_SET_OPTION command to set options for the current connection. Currently only CLIENT_MULTI_STATEMENTS can be set.

For example, you can disable CLIENT_MULTI_STATEMENTS with this command.

connection.setOption(MySQLSetOption.MYSQL_OPTION_MULTI_STATEMENTS_OFF, { ar ->
  if (ar.succeeded()) {
    println("CLIENT_MULTI_STATEMENTS is off now")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

MySQL and MariaDB version support matrix

MySQL MariaDB

Version

Supported

Version

Supported

5.5

10.1

5.6

10.2

5.7

10.3

8.0

10.4

Known issues:

  • Reset connection utility command does not work in MySQL 5.5, 5.6 and MariaDB 10.1

  • Change user utility command is not supported with MariaDB 10.2 and 10.3

Pitfalls & Good Practices

Here are some good practices for you to avoid common pitfalls when using the Reactive MySQL Client.

prepared statement count limit

Sometimes you might meet the notorious error Can’t create more than max_prepared_stmt_count statements (current value: 16382), this is because the server has reached the limit of total number of prepared statement.

You can adjust the server system variable max_prepared_stmt_count but it has an upper bound value so you can’t get rid of the error in this way.

The best way to alleviate this is enabling prepared statement caching, so the prepared statements with the same SQL string could be reused and the client does not have to create a brand new prepared statement for every request. The prepared statement will be automatically closed when it’s evicted from the cache. In this way the chances of reaching the limit could be greatly reduced though it could not be totally eliminated.

Note using SqlClient#preparedQuery without prepared statement caching enabled will not close the prepared statement after executing!

You can also manage the lifecycle of prepared statements manually by creating a PreparedQuery object via SqlConnection#prepare interface, or even use the SQL syntax prepared statement.

demystifying prepared batch

There is time when you want to batch insert data into the database, you can use SqlClient#preparedBatch which provides a simple API to handle this. Keep in mind that MySQL does not natively support batching protocol so the API is only a sugar by executing the prepared statement one after another, which means more network round trips are required comparing to inserting multiple rows by executing one prepared statement with a list of values.

tricky DATE & TIME data types

Handling MYSQL DATE and TIME data types especially with time zones is tricky therefore the Reactive MySQL Client does no magic transformation for those values.

  • MySQL DATETIME data type does not contain time zone info, so what you get is identical to what you set no matter what time zone is in the current session.

  • MySQL TIMESTAMP data type contains time zone info, so when you set or get the value it’s always transformed by the server with the timezone set in the current session.