Chapter 159. Websocket

Websocket Component

Available as of Camel 2.10
The websocket component provides websocket endpoints for communicating with clients using websocket. The component uses Eclipse Jetty Server which implements the IETF specification (drafts and RFC 6455). It supports the protocols ws:// and wss://. To use wss:// protocol, the SSLContextParameters must be defined.
Version currently supported
As Camel 2.10 uses Jetty 7.5.4.v20111024, only the D00 to D13 IETF implementations are available. Camel 2.11 uses Jetty 7.6.7.

URI format

websocket://hostname[:port][/resourceUri][?options]
You can append query options to the URI in the following format, ?option=value&option=value&...

Component Options

The WebsocketComponent can be configured prior to use, to setup host, to act as a websocket server.
Option Default Description
host 0.0.0.0 The hostname.
port 9292 The port number.
staticResources null Path for static resources such as index.html files etc. If this option has been configured, then a server is started on the given hostname and port, to service the static resources, eg such as an index.html file. If this option has not been configured, then no server is started.
sslContextParameters Reference to a org.apache.camel.util.jsse.SSLContextParameters in the Registry. This reference overrides any configured SSLContextParameters at the component level. See Using the JSSE Configuration Utility.
enableJmx false If this option is true, Jetty JMX support will be enabled for this endpoint.
sslKeyPassword null Consumer only: The password for the keystore when using SSL.
sslPassword null Consumer only: The password when using SSL.
sslKeystore null Consumer only: The path to the keystore.
minThreads null Consumer only: To set a value for minimum number of threads in server thread pool.
maxThreads null Consumer only: To set a value for maximum number of threads in server thread pool.
threadPool null Consumer only: To use a custom thread pool for the server.

Endpoint Options

The WebsocketEndpoint can be configured prior to use
Option Default Description
sslContextParametersRef Deprecated and will be removed in Camel 3.0: Reference to a org.apache.camel.util.jsse.SSLContextParameters in the Registry. This reference overrides any configured SSLContextParameters at the component level. See Using the JSSE Configuration Utility. Use the sslContextParameters option instead
sslContextParameters Camel 2.11.1: Reference to a org.apache.camel.util.jsse.SSLContextParameters in the Registry. This reference overrides any configured SSLContextParameters at the component level. See Using the JSSE Configuration Utility.
sendToAll null Producer only: To send to all websocket subscribers. Can be used to configure on endpoint level, instead of having to use the WebsocketConstants.SEND_TO_ALL header on the message.
staticResources null The root directory for the web resources or classpath. Use the protocol file: or classpath: depending if you want that the component loads the resource from file system or classpath.
sslContextParameters
Reference to a org.apache.camel.util.jsse.SSLContextParameters in the Registry. This reference overrides any configured SSLContextParameters at the component level. See Using the JSSE Configuration Utility.
enableJmx
false
If this option is true, Jetty JMX support will be enabled for this endpoint. See Jetty JMX support for more details.
sslKeyPassword
null
Consumer only: The password for the keystore when using SSL.
sslPassword
null
Consumer only: The password when using SSL.
sslKeystore
null
Consumer only: The path to the keystore.
minThreads
null
Consumer only: To set a value for minimum number of threads in server thread pool.
maxThreads
null
Consumer only: To set a value for maximum number of threads in server thread pool.
threadPool
null
Consumer only: To use a custom thread pool for the server.

Message Headers

The websocket component uses 2 headers to indicate to either send messages back to a single/current client, or to all clients.
Key Description
WebsocketConstants.SEND_TO_ALL Sends the message to all clients which are currently connected. You can use the sendToAll option on the endpoint instead of using this header.
WebsocketConstants.CONNECTION_KEY Sends the message to the client with the given connection key.

Usage

In this example we let Camel exposes a websocket server which clients can communicate with. The websocket server uses the default host and port, which would be 0.0.0.0:9292. The example will send back an echo of the input. To send back a message, we need to send the transformed message to the same endpoint "websocket://echo". This is needed because by default the messaging is InOnly.
// expose a echo websocket client, that sends back an echo
from("websocket://echo")
    .log(">>> Message received from WebSocket Client : ${body}")
    .transform().simple("${body}${body}")
    // send back to the client, by sending the message to the same endpoint
    // this is needed as by default messages is InOnly
    // and we will by default send back to the current client using the provided connection key
    .to("websocket://echo");
This example is part of an unit test, which you can find here. As a client we use the AHC library which offers support for web socket as well.
Here is another example where webapp resources location have been defined to allow the Jetty Application Server to not only register the WebSocket servlet but also to expose web resources for the browser. Resources should be defined under the webapp directory.
from("activemq:topic:newsTopic")
   .routeId("fromJMStoWebSocket")
   .to("websocket://localhost:8443/newsTopic?sendToAll=true&staticResources=classpath:webapp");

Setting up SSL for WebSocket Component

Using the JSSE Configuration Utility

As of Camel 2.10, the WebSocket component supports SSL/TLS configuration through the Camel JSSE Configuration Utility. This utility greatly decreases the amount of component specific code you need to write and is configurable at the endpoint and component levels. The following examples demonstrate how to use the utility with the Cometd component.

Programmatic configuration of the component

KeyStoreParameters ksp = new KeyStoreParameters();
ksp.setResource("/users/home/server/keystore.jks");
ksp.setPassword("keystorePassword");

KeyManagersParameters kmp = new KeyManagersParameters();
kmp.setKeyStore(ksp);
kmp.setKeyPassword("keyPassword");

TrustManagersParameters tmp = new TrustManagersParameters();
tmp.setKeyStore(ksp);

SSLContextParameters scp = new SSLContextParameters();
scp.setKeyManagers(kmp);
scp.setTrustManagers(tmp);

CometdComponent commetdComponent = getContext().getComponent("cometds", CometdComponent.class);
commetdComponent.setSslContextParameters(scp);

Spring DSL based configuration of endpoint

...
  <camel:sslContextParameters
      id="sslContextParameters">
    <camel:keyManagers
        keyPassword="keyPassword">
      <camel:keyStore
          resource="/users/home/server/keystore.jks"
          password="keystorePassword"/>
    </camel:keyManagers>
    <camel:trustManagers>
      <camel:keyStore
          resource="/users/home/server/keystore.jks"
          password="keystorePassword"/>
    </camel:trustManagers>
  </camel:sslContextParameters>...
...
  <to uri="websocket://127.0.0.1:8443/test?sslContextParameters=#sslContextParameters"/>...

Java DSL based configuration of endpoint

...
    protected RouteBuilder createRouteBuilder() throws Exception {
        return new RouteBuilder() {
            public void configure() {

                String uri = "websocket://127.0.0.1:8443/test?sslContextParameters=#sslContextParameters";

                from(uri)
                     .log(">>> Message received from WebSocket Client : ${body}")
                     .to("mock:client")
                     .loop(10)
                         .setBody().constant(">> Welcome on board!")
                         .to(uri);
...