Chapter 21. Cometd

Cometd Component

The cometd: component is a transport for working with the jetty implementation of the cometd/bayeux protocol. Using this component in combination with the dojo toolkit library it's possible to push Apache Camel messages directly into the browser using an AJAX based mechanism.

URI format

cometd://host:port/channelName[?options]
The channelName represents a topic that can be subscribed to by the Apache Camel endpoints.

Examples

cometd://localhost:8080/service/mychannel
cometds://localhost:8443/service/mychannel
where cometds: represents an SSL configured endpoint.

Options

Name Default Value Description
resourceBase 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. Classpath is required for OSGI deployment where the resources are packaged in the jar
baseResource Camel 2.7: 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. Classpath is required for OSGI deployment where the resources are packaged in the jar
timeout 240000 The server side poll timeout in milliseconds. This is how long the server will hold a reconnect request before responding.
interval 0 The client side poll timeout in milliseconds. How long a client will wait between reconnects
maxInterval 30000 The max client side poll timeout in milliseconds. A client will be removed if a connection is not received in this time.
multiFrameInterval 1500 The client side poll timeout, if multiple connections are detected from the same browser.
jsonCommented true If true, the server will accept JSON wrapped in a comment and will generate JSON wrapped in a comment. This is a defence against Ajax Hijacking.
logLevel 1 0=none, 1=info, 2=debug.
sslContextParameters Camel 2.9: 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.
crossOriginFilterOn false Camel 2.10: If true, the server will support for cross-domain filtering
allowedOrigins * Camel 2.10: The origins domain that support to cross, if the crosssOriginFilterOn is true
filterPath Camel 2.10: The filterPath will be used by the CrossOriginFilter, if the crosssOriginFilterOn is true
disconnectLocalSession true Camel 2.10.5/2.11.1: (Producer only): Whether to disconnect local sessions after publishing a message to its channel. Disconnecting local session is needed as they are not swept by default by CometD, and therefore you can run out of memory.
You can append query options to the URI in the following format, ?option=value&option=value&...
Here is some examples of how to pass the parameters.
For file (when the Webapp resources are located in the Web Application directory) cometd://localhost:8080?resourceBase=file./webapp. For classpath (when the web resources are packaged inside the Webapp folder) cometd://localhost:8080?resourceBase=classpath:webapp.

Authentication

Available as of Camel 2.8
You can configure custom SecurityPolicy and Extension's to the CometdComponent which allows you to use authentication as documented here

Setting up SSL for Cometd Component

Using the JSSE Configuration Utility

As of Camel 2.9, the Cometd 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. You need to configure SSL on the CometdComponent class.

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:keyManagers>
  </camel:sslContextParameters>

  <bean id="cometd" class="org. apache. camel. component.cometd.CometdComponent">
    <property name="sslContextParameters" ref="sslContextParameters"/>
  </bean>
  ...
  <to uri="cometds://127.0.0.1:443/service/test?baseResource=file:./target/test-classes/webapp&timeout=240000&interval=0&maxInterval=30000&multiFrameInterval=1500&jsonCommented=true&logLevel=2&sslContextParameters=#sslContextParameters"/>...