It is possible in 2.2 and 2.4 to manipulate an interceptor stack at runtime using JMX :

http://fisheye.jboss.org/viewrep/~raw,r=1.10/JBoss/jboss-portal/server/src/main/org/jboss/portal/server/impl/invocation/JBossInterceptorStack.java

however that will probably not work in 3.x serie when we refactor around the microcontainer.

In addition to Julian's answer I can give a usage example.
This is a snippet of an interceptor that injects itself into the server interceptor chain:

/**
 * Injects the LocaleInterceptor into the Server InterceptorStack.
 * @throws Exception
 */
protected void startService() throws Exception {

 ObjectName name = getInterceptorStack();
 Object [] params = new Object[] {this.serviceName};
 String [] signature = new String [] {ObjectName.class.getName()};

 // Add the interceptor
 server.invoke(name, "addInterceptor", params, signature);

 // Rebuild the interceptor chain
 server.invoke(name, "rebuild", new Object[]{}, new String[]{});
}

/**
 * Removes the LocaleInterceptor from the Server InterceptorStack.
 * @throws Exception
 */
protected void stopService() throws Exception {

 ObjectName name = getInterceptorStack();
 Object [] params = new Object[] {this.serviceName};
 String [] signature = new String [] {ObjectName.class.getName()};

 // Remove the interceptor
 server.invoke(name, "removeInterceptor", params, signature);

 // Rebuild the interceptor chain
 server.invoke(name, "rebuild", new Object[]{}, new String[]{});
}

Hello,

My name is tom. I have some questions for you.I'm developing an interceptor to read the HttpSession for an attribute (e.g. thePortalLanguage )
from a portlet that changes the portal's language.

But when i access this attribute within the invoke method it is null. I observed that the session is accessed firstly from the interceptor an after from my servlet that sets the attribute. Why is that?

Secondly i would like to ask you about the snippet that injects itself. Obviously these are two extra methods inside the interceptor, right?

I cant figure out the methods getInterceptorStack() and your server variable, is it invocation.getRequest().getServer() ??

And what about serviceName variable?

Thank you!