Jean-Francois Arcand's Blog

Extending GlassFish's WebContainer

The GlassFish WebContainer is based on the Tomcat Servlet implementation called Catalina. The Catalina architecture, introduced in Tomcat 4.x, was designed to easily allow developer to extends it. There is several interception point in Catalina that can be extended:

• Valve: A Valve is a request processing component associated with a particular virtual-server(host) or web-module (servlet). A series of Valves are generally associated with each other into a Pipeline. Developer will usually inject their valves in order to have access to the Catalina internal objects, and manipulate the request/response object before filters or servlets are invoked. As an example, the access logging mechanism in GlassFish is implemented as a Valve.
• ContainerListener: A listener for significant Container generated events. As an example, every time a WAR is deployed, a ContainerListener implementation will be notified for every new created Servlet, TagLib or Filter.
• InstanceListener: A listener for significant events related to a specific servlet instance. An implementation of this interface will get notified everytime a Servlet is about to be invoked or when some operations are made on the Servlet (like when calling its ServletContextListeners).
• LifecycleListener: A listener for significant events (including "virtual server start" and "web module stop") generated by a component that implements the Lifecycle interface. An implementation of this interface will get notified by mostly all internal objects when an it is started|stopped (like when a new virtual-server is created). As an example, we are using this interface internally to notify the other GlassFish's containers.

Virtual server supports the injection of Valve, ContainerListener and LifecycleListener. Web module supports the same as the virtual server with the addition of the InstanceListener.

Once you have your extension implemented, you need to install it in GlassFish. To install an extension:

For virtual-server

• Add your classes into a jar file (ex: glassfish-ext.jar)
• Place your jar under ${glassfish.home}/lib
• Edit ${glassfish.home}/domains/domain1/config/domain.xml, locate the virtual-server element, and add <property name="type" value="fully qualified class name"> where type can be valve_ or listener_, with a unique number allowing you to define more than one type.

  Ex: <property name="valve_1" value="org.apache.catalina.valves.RequestDumperValve"/>

For web-module

• Same as for virtual-server, but under the web-module element of domain.xml. Except you can bundle your implementation under WEB-INF/lib or WEB-INF/classes (easier to deploy to several GlassFish installations)

  Ex: <property name="listener_1" value="org.glassfish.MyServletListener"/>

Very easy, is it :-). This is supported starting in GlassFish v2 build 17.

technorati: web container glassfish

Comments

• Hi Jean-Francois,

  You should check out the trace and jvm insight extensions we have created specifically for Tomcat which could easily be integrated into Glassfish as we do for JBoss AS / Apache Tomcat today. The benefit of our integration is that you get an awarding winning management console to analysis the performance profile and perform on-demand runtime object state inspections.

  JXInsight 4.2.2 - Apache Tomcat Monitoring
  http://blog.jinspired.com/?p=16

  JXInsight 4.2.2 - Inspecting WebApps
  http://blog.jinspired.com/?p=17

  
  Regards,

  William Louth
  JXInsight Product Architect
  JInspired

  "Java EE tuning, testing, tracing, and monitoring with JXInsight"
  http://www.jinspired.com

  Posted by: williamlouth on September 11, 2006 at 11:57 AM

• Hi William, this is interesting :-) Our Valve API is a little different than the one in Tomcat, so you might need to change your API a little. -- Jeanfrancois

  Posted by: jfarcand on September 11, 2006 at 01:30 PM

• Hello Jean ,

  How would you include the Remote Address Filter?

  
  
  
  
  
  

  -->
  

  
  -Fret

  Posted by: fret on June 29, 2007 at 08:12 AM

• I am trying to use Valves, and I am a little confused a few things.

  1. by the versioning terminology of Glassfish. I am using Sun Java System Application Server 9.1 (build b50g-beta3) - it seems like that would have the support for Valves, but I can't seem to get Valves to work.

  2. I noticed that the Valve API (as you point out in the comment above) is different from Catalina's. Is there documentation (beyond the JavaDoc linked above) on the version used in Glassfish, and a discussion of the motivations and implications?

  Question 1 is there because I cannot get the Valve to load or work. I don't know how to verify that a Valve was loaded, and certainly it isn't doing its job as far as add headers is concerned.

  Thanks!
  Benjamin

  Posted by: br_31 on August 28, 2007 at 04:18 AM

• Never mind my previous posting.

  I figured it out - the importance of the property naming ("valve_XXX") escaped me the first time.

  Another question regarding this:

  If the user is deploying a J2EE application (EAR) there is no web-module entry in domain.xml. Is there a way to configure a valve at the web-module level then?

  Thanks,
  Benjamin

  Posted by: br_31 on August 28, 2007 at 04:58 AM

• Hi Benjamin,

  can we continue the discussion on users@glassfish.dev.java.net so more people can reply (and more faster response :-)). Can you elaborate on what you want to do? I suspect you may want to read this. as I suspect it may help. See you on the users list :-)

  Thanks! -- Jeanfrancois

  Posted by: jfarcand on August 28, 2007 at 07:16 AM

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