What's new in Vert.x 4.2

Vert.x 4.2 comes with plenty of new ex­cit­ing fea­tures.

Here is an overview of the most im­por­tant fea­tures sup­ported in Vert.x 4.2.

Java 17

Vert.x 4.2 comes with of­fi­cial sup­port of Java 17.

Our CI has been up­dated to test from our Java 8 base­line to the very re­cent Java 17 re­lease.

Reactive SQL Clients

Oracle client

The Re­ac­tive Or­a­cle Client joins the data­base clients fam­ily!

This client is in tech pre­view and we are eager to hear any feed­back you may have.

Microsoft SQL Server client


The Re­ac­tive SQL Server Client is able to ne­go­ti­ate the en­cryp­tion level when a con­nec­tion is es­tab­lished:

  • no en­cryp­tion
  • en­crypt login packet only
  • en­crypt en­tire con­nec­tion

Azure SQL Database

Our client is now able to con­nect to Azure SQL Data­base servers.

This was made pos­si­ble thanks to:

MQTT Server V5 support

The MQTT Server has been up­graded to sup­port the ver­sion 5 of the pro­to­col par­tially (the auth mes­sage re­mains to be im­ple­mented).

Cassandra Client

The Cas­san­dra Client can trace query ex­e­cu­tion when Vert.x has trac­ing en­abled.

The client re­ports the fol­low­ing client spans:

  • Query op­er­a­tion name
  • tags
    • peer.address: list of nodes known to the dri­ver, in the form [127_0_0_1:9042,localhost:9042,myhost_mydomain:9042]
    • span.kind: client
    • db.instance: the key­space
    • db.statement: the CQL query
    • db.type: cassandra

Web Client enhancements

Our Web Client sup­ports now Oauth2 au­to­mated token se­cu­rity man­age­ment.

WebClient client = WebClient.create(vertx);
OAuth2WebClient oauth2 = OAuth2WebClient.create(
    OAuth2Auth.create(vertx, new OAuth2Options(/* enter IdP config */)))

  // configure the initial credentials (needed to fetch if needed
  // the access_token
  .withCredentials(new TokenCredentials("some.jwt.token"));

To­kens are now fetched or re­freshed dur­ing the life­cy­cle of the client.

It also of­fers an HTTP re­sponse caching fa­cil­ity.

WebClient client = WebClient.create(vertx);
WebClient cachingWebClient = CachingWebClient.create(client);

Auth enhancements


We­bau­thn now sup­ports MDS3. The now “legacy” MDS2 is still avail­able as the ser­vice is ex­pected to be run­ning until Nov 2022. In terms of usage, noth­ing changed, the mod­ule can iden­tify the meta­data ver­sion from the pay­load and de­cide how to han­dle it in­ter­nally.


A new mod­ule and han­dler for 2nd fac­tor au­then­ti­ca­tion is now avail­able:

OtpAuthHandler otp = OtpAuthHandler.create(TotpAuth.create();

  // the issuer for the application
  .issuer("Vert.x Demo")
  // handle code verification responses
  // handle registration of authenticators
  // handle verification of authenticators

This mod­ule and han­dler are com­pat­i­ble with google au­then­ti­ca­tor and sim­i­lar apps.


When using Ope­nAPI and event­bus de­ployed ser­vices, when de­ploy­ing se­cure APIs, the HTTP Authorization header is now prop­a­gated along with the re­quest all the way with the re­quest on the event­bus. This paves the way to cre­ate a Zero Trust foun­da­tion for vert.x dis­trib­uted ap­pli­ca­tions.

Redis Client

Redis client now sup­port REPLICATION mode. This mode is com­monly used by cloud providers like Azure and AWS. The client will act just like in a clus­tered mode, with less over­head as the host­ing will per­form most of the clus­tered tasks, not the client.

      new RedisOptions()
      .onSuccess(conn -> {
        // this is a replication client.
        // write operations will end up in the master node
        // and read operations will end up in the replica nodes if available

Vert.x Web GraphQL

Context Management

Vert.x Web GraphQL has been up­graded to GraphQL-​Java ver­sion 17. In this ver­sion, the GraphQLContext ob­ject be­comes the stan­dard to share con­tex­tual data be­tween com­po­nents of a GraphQL Java ap­pli­ca­tion (see v17 Re­lease Notes).

Con­se­quently, we have:

GraphQL over Websockets protocol

The Apollo subscriptions-transport-ws li­brary is not being ac­tively main­tained. It is rec­om­mended that you use the graphql-ws in your client ap­pli­ca­tions li­brary in­stead.

For this pur­pose, Vert.x Web GraphQL sup­ports the GraphQL over Web­sock­ets pro­to­col.

For de­tails about it, please read the GraphQL over Web­Sock­ets an­nounce­ment.

Vert.x JUnit 5

By de­fault the thread in­vok­ing the test meth­ods is the JUnit thread. The io.vertx.junit5.RunTestOnContext ex­ten­sion can be used to alter this be­hav­ior by run­ning test meth­ods on a Vert.x event-​loop thread.

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