Release Notes


Java 11 Support

This release requires Java 11. JAXB has been pulled in as external dependency, since it's no longer part of the JDK.

Transport Connectors

Transport Connectors now let you chose among multiple implementations for a given connection method, e.g. for TCP binding you can choose between JDK's Socket or Netty's Channel.

See Basic Concepts


New Project Structure and Modularization

The following artifacts have been renamed:

  • xmpp-core => xmpp-core-common
  • xmpp-extensions => xmpp-extensions-common
  • xmpp-websocket => xmpp-websocket-common + xmpp-websocket-client

Experimental work on a server implementation has revealed, that it's useful to have a “common” module of -let's say- the WebSocket implementation, which now includes codecs, which can be used likewise by a client and server implementation. The “common” artifacts therefore contain code, which could be shared by clients and servers.

Jid is now an interface


  1. The old Jid class always constructed a new instance with every call of asBareJid(). The interface now allows to reference the enclosing class' fields and returning only a “bare” view of the enclosing Jid instead of creating new instances. This is a performance improvement to avoid creating too many objects and decreases GC pressure.

  2. Jid being an interface allows for more flexibility. E.g. there's now a package-private MalformedJid implementation, which is internally used during parsing and allows to send a malformed-jid stanza error.

Update PRECIS to RFC 8264

The XMPP Address Format uses PRECIS for internationalizing the local part. The previous Jid implementation used RFC 7564, which case folded the Jid's local part. The updated PRECIS specification RFC 8264 only lower cases it. This has the following impact:

Old Jid behavior:

Jid jid = Jid.of('fußball@domain');
// jid.toString() == "fussball@domain"

New Jid behavior:

Jid jid = Jid.of('fußball@domain');
// jid.toString() == "fußball@domain"

Java NIO Support

There's a new artifact xmpp-nio-netty-client, which enables you to use Java NIO for TCP connections using the Netty framework.

Background: The current (and default) implementation (see TcpConnectionConfiguration) uses two threads per connection, one for reading, one for writing. This is required, because it uses internally, which uses blocking IO. For most client applications this is not an issue and totally acceptable, because clients rarely open multiple connections.

However, the advantage of NIO is that it doesn't use blocking IO, so now you can use only one (!) thread for a large number of connections:

NioEventLoopGroup eventLoopGroup = new NioEventLoopGroup(1);

NettyTcpConnectionConfiguration tcpConnectionConfiguration = NettyTcpConnectionConfiguration.builder()

for (int i = 0; i < 100; i++) {
    XmppClient xmppClient = XmppClient.create("localhost", configuration, tcpConnectionConfiguration);

As you can see, you can reuse the same NioEventLoopGroup for multiple connection configurations.

XEP-0392: Consistent Color Generation

Sample usage:

ConsistentColor color = ConsistentColor.generate(input);
float red = color.getRed();
float green = color.getGreen();
float blue = color.getBlue();

(float is used for easier integration with java.awt.Color.)

Custom ThreadFactory

For all threads being started you can now specify a custom thread factory. This might be useful when using this library in Java EE with a ManagedThreadFactory:

private ManagedThreadFactory mtf;
XmppSessionConfiguration configuration = XmppSessionConfiguration.builder()

Major API changes

  • new rocks.xmpp.core.Text class to represent texts in XMPP (Message, Subjects, Errors). The affected classes use the new class now.
  • class rocks.xmpp.core.session.Connection became an interface
  • rocks.xmpp.core.session.ConnectionConfiguration became
  • new enum ChannelEncryption to set the behavior, if, how and when a channel should be encrypted (e.g. direct or via StartTLS)
  • rocks.xmpp.websocket.WebSocketConnection became
  • rocks.xmpp.websocket.WebSocketConnectionConfiguration became