部署到weblogic时的Java LinkageError

Question

I am working on a big application and I just added a new web service generated by eclipse with the help of axis. The application runs fine in my development environment (where the application is hosted by jetty) but now I am having trouble when running my application in weblogic (where the application needs to be deployed). The error I am getting is:

java.lang.LinkageError: loader constraint violation in interface
itable initialization: when resolving method
"org.apache.axis.client.Service.getServiceName()Ljavax/xml/namespace/QName;"
the class loader (instance of
weblogic/utils/classloaders/ChangeAwareClassLoader) of the current
class, org/apache/axis/client/Service, and the class loader (instance
of sun/misc/Launcher$AppClassLoader) for interface
javax/xml/rpc/Service have different Class objects for the type
getServiceName used in the signature

This issue is delaying development for days already. As I understand from looking on the web:

• My Axis dependency contains the class: org.apache.axis.client.Service which follows the javax.xml.rpc.Service interface.
• My Weblogic provided the interface: javax.xml.rpc.Service
• Since they are in a different path (application and weblogic) they are loaded by different classloaders

1st question: Are my observations correct?

2nd question: What can I do/try to resolve this?

Extra information:

• Using Maven.
• To make sure all dependencies loaded by Weblogic are also available in our development environment we added the wlsfullclient.jar as a dependency (only in our dev env).
• Since our weblogic server is used by a lot of projects I can not just add the Axis jar to the weblogic path.
• I found a similar issue already on Stack: How to deal with LinkageErrors in Java? .
  • Their solution is not clear for me though I am interested in Alex Miller's reply, specifically: "That may mean removing it from the classpath and loading as a plugin".
    • Does this apply on the application side or is this the web logic side?
• If more information is required I will gladly provide it.

EDIT: I have a weblogic.xml in my project with the following content:

<?xml version='1.0' encoding='UTF-8'?>
  <weblogic-web-app >
    <container-descriptor>
      <prefer-web-inf-classes>true</prefer-web-inf-classes>
    </container-descriptor>
  <context-root>auditgui</context-root>
</weblogic-web-app>

The structure of my WAR file is as follows:

file.war
    |--crossdomain.xml
    |--robots.txt
    |--META-INF
    |   \--MANIFEST.MF
    |--WEB-INF
    |   |--classes
    |   |   |--com
    |   |   |   \--...
    |   |   |--spring
    |   |   |   |--main-context.xml
    |   |   |   \--security-context.xml
    |   |   \--environment-beans.xml
    |   |--lib
    |   |   \--multiplejars.jar
    |   |--spring
    |   |   |--raw-servlet-context.xml
    |   |   |--root-context.xml
    |   |   \--servlet-context.xml
    |   |--web.xml
    |   \--weblogic.xml
    |--css
    |   \--multipleCSSFiles.css
    |--js
    |   \--multipleJSFiles.js...
    |--img
    |   \--muultipleImages.png...
    \--multipleHTMLFiles.html...

Answer 1

Ok I solved the issue. I found the conflicting dependencies;

Recap:

Using the

weblogic-web-app/container-descriptor

did not work for me:

prefer-web-inf-classes = true

was already set and changing it to prefer application packages only caused more trouble since the project already depended on the prefer classes configuration.

Solution:

I used findjar for looking up in which jar's my QName resides and put these jar's in my memory.

Then by using

mvn dependency:tree

I got all the dependencies and sub dependencies of my project (wont post it because the POM is BIG).

I noticed that there were two dependencies with 'stax' in their name. One 'official' stax jar (sub dependency of xmlbeans) and one from genronimo (sub dependency of axiom). So I did some research and found out that the geronimo stax is an implementation/adaption on the original stax jar and therefore both contain QName. I removed the original stax from my dependency list:

    <dependency>
        <groupId>org.apache.xmlbeans</groupId>
        <artifactId>xmlbeans</artifactId>
        <version>2.5.0</version>
        <!-- Excluding XMLBean's STAX because we want to use axiom/geronimo-stax -->
        <exclusions>
            <exclusion>
                <groupId>stax</groupId>
                <artifactId>stax-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

Hope it helps :)

Answer 2

You can tell WebLogic to use your application classes by adding prefer-web-inf-classes to the weblogic.xml in your WAR file.

<weblogic-web-app>
<container-descriptor>
<prefer-web-inf-classes>true</prefer-web-inf-classes>
</container-descriptor>
</weblogic-web-app>

Answer 3

WebLogic will also let you specify which packages to use from your app vs. from the WLS classpath:

<weblogic-web-app>
  <container-descriptor>
    <prefer-application-packages>
      <package-name>org.apache.commons.*</package-name>
      <package-name>org.apache.log4j.*</package-name>
      <package-name>org.slf4j.*</package-name>
    </prefer-application-packages>
  </container-descriptor>
</weblogic-web-app>

prefer-web-inf-classes means that what's packaged in the app always takes precedence over WebLogic's settings, which may or may not be a good thing.