JBoss ClassLoading Parent-Last loading

Question

I wanted to understand parent-last loading in an application JBoss application server. We have a legacy application deployed in JBoss 4.2.1 GA. For which we are trying the parent-last loading.

I am referring to the this link. I wanted to learn a parent last loading. So had created simple maven jar package application with maven-jar-plugin and configuration -> addDefaultImplementationEntries = true. I have created 2 jar versions 1.0.0 and 1.0.1 from the same jar creation maven application. The jar has single class TestClass and a simple String return method that returns the version of the jar the class is loaded from. what I wanted to experience the use of java2ClassLoadingCompliance. I have packaged the version 1.0.0 jar in the server/deploy/MyApplication/WEB-INF/lib (My web application is a simple servlet application that calls the method of the class thus printing the version number from which jar it was called from.) and version 1.0.1 jar in server/lib.

Note : Logically it does not make sense to use an older version of jar in application and overriding it with the newer version present in server lib, but just wanted to experience the class loading.

I have tried the following

Without any jboss-web.xml in the meta-inf folder.
I tried introduction jboss-we.xml in META-INF and doing the same with java2ClassLoadingCompliance = false.
With java2ClassLoadingCompliance = true.

All the time class from the application lib would get loaded by the application.

My jboss-web.xml looks like reference

<jboss-web>
   <class-loading java2ClassLoadingCompliance="true">
      <loader-repository>
         com.example:archive=JBossClassLoadingTestServlet-0.0.1-SNAPSHOT.ear
         <loader-repository-config>java2ParentDelegation=true</loader-repository-config>
      </loader-repository>
   </class-loading>
</jboss-web>

Can someone help me understanding parent-last configuration in JBoss? What is the mistake I am doing here that always class from application lib gets loaded?

Oh god JBoss 4.2, what is wrong with you? :-o – Aaron Mar 04 '17 at 14:18 — Aaron, Mar 04 '17 at 14:18

score 0 · Answer 1 · edited May 23 '17 at 11:53

I am afraid that your link is not so related to your experiment. It is more related about the EAR deployments, in which there exists multi-module deployments and need multiple versions of the lib to isolate.

In your case, you just override lib in one Jar.

The following is from Servlet Spec:

It is recommended also that the application class loader is implemented so that classes and resources packaged within the WAR are loaded in preference to classes and resources residing in container-wide library JARs.

So, JBoss follow the spec and it always loads application lib first.

I didn't find such old version doc, but it should similar as AS7:

In order of highest priority to lowest priority

System Dependencies - These are dependencies that are added to the module automatically by the container, including the Java EE APIs.

User Dependencies - These are dependencies that are added through JBoss-deployment-structure.xml or through the Dependencies: manifest entry.

Local Resource - Class files packaged up inside the deployment itself, e.g. class files from WEB-INF/classes or WEB-INF/lib of a war.

Inter-deployment dependencies - These are dependencies on other deployments in an ear deployment. This can include classes in an ear's lib directory, or classes defined in other EJB jars.

a similar jetty classloading problem

JBoss ClassLoading Parent-Last loading

1 Answers1