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Chapter 24. 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 an org.apache.camel.util.jsse.SSLContextParameters object in the Registry. This reference overrides any configured SSLContextParameters at the component level. See chapter "Configuring Transport Security for Camel Components" in "Security Guide" and 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
|
false
|
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
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 example demonstrates a Spring DSL-based configuration of the endpoint. You need to configure SSL on the
CometdComponent class.
...
<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"/>...
