On May 28, 2010, at 3:22 PM, SunSeaAndPalms wrote:
>
> Technologies that are used in my application requires classloader with
> 'addTransformer(ClassFileTransformer)' method and claims that Geronimo's
> default org.apache.geronimo.kernel.config.MultiParentClassLoader , doesn't
> have it. So I need to setup my special class loader for my application
> (war). I use Geronimo with Tomcat. I was told that specifying classloader is
> a very simple process on Tomcat. Following example shows how to do it (The
> file is named "context.xml"):
>
> <Context path="/myWebApp" docBase="/my/webApp/location">
> <Loader
>
> loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader"/>
> </Context>
>
> The alternative for Geronimo is using "geronimo-tomcat.xml" in deployment
> plan (I read about it from
> http://www.ibm.com/developerworks/java/library/os-ag-tomcat/ this doc ). The
> problem is that there isn't a classloader property specified.
>
> So my question is: How can I change default classloader with a special one
> for my web application deployed on Geronimo?
You can't change what classloader geronimo uses for your web app. However, you
can register a ClassTransformer quite easily. We do this for jpa. Here's the
code we use, from 2.2
plugins/openjpa/geronimo-persistence-jpa10/src/main/java/org/apache/geronimo/persistence/PersistenceUnitGBean.java:
public void addTransformer(ClassTransformer classTransformer) {
TransformerWrapper transformer = new
TransformerWrapper(classTransformer, classLoader);
transformers.add(transformer);
TransformerAgent.addTransformer(transformer);
}
public class TransformerWrapper implements ClassFileTransformer {
private final ClassTransformer classTransformer;
private final ClassLoader classLoader;
public TransformerWrapper(ClassTransformer classTransformer, ClassLoader
classLoader) {
this.classTransformer = classTransformer;
this.classLoader = classLoader;
}
public byte[] transform(ClassLoader loader, String className, Class<?>
classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer)
throws IllegalClassFormatException {
if (loader != classLoader) {
return null;
}
try {
return classTransformer.transform(loader, className,
classBeingRedefined, protectionDomain, classfileBuffer);
} catch (IllegalClassFormatException e) {
throw e;
} catch (RuntimeException e) {
return null;
}
}
}
If you don't care whether all classes, not just the ones in your app, are fed
to your ClassTransformer, you can leave out the TransformerWrapper.
This code should go in a gbean with priority PRIORITY_CLASSLOADER to make sure
it is installed before other components are started and perhaps load your
classes untransformed. See the PersistenceUnitGBean for more details.
Hope this helps
david jencks
>
>
> --
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