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CometD 2 & Servlet Containers

CometD 2 Configuration in Servlet Containers

CometD relies on Jetty Continuations, a library that is portable among servlet containers.

While CometD 2 runs natively in Jetty 7 and in Servlet 3 compliant servlet containers, it requires additional configuration for other servlet containers such as Jetty 6 or Tomcat 6.

These other servlet containers need a ContinuationFilter to be configured for the paths that make use of Jetty Continuations (in CometD this path is usually "/cometd/*"), for example:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
         version="2.5">

    <servlet>
        <servlet-name>cometd</servlet-name>
        <servlet-class>org.cometd.server.CometdServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>cometd</servlet-name>
        <url-pattern>/cometd/*</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>continuation</filter-name>
        <filter-class>org.eclipse.jetty.continuation.ContinuationFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>continuation</filter-name>
        <url-pattern>/cometd/*</url-pattern>
    </filter-mapping>
</web-app>

In this example, the CometdServlet, which makes use of Jetty Continuations, is mapped to /cometd/*, and therefore the ContinuationFilter must also be mapped on that path.