Custom Loaders

[webmaster <we...@michaelmcgrady.com>]

I am trying to use a custom loader for a utility class for an Action 
class.  This is not working.  The utility tests fine off the net.  When I 
get it on the net and in Tomcat, it breaks.  The loader is for a hot 
deploy.  The following is the code.  Can anyone tell me why this 
breaks?  It returns a good Class object but when initializing a variable 
for Class with Tomcat and Struts, it throws a null pointer exception.  That 
is an odd thing, since nothing is null.  But, I suspect it must be because 
of some classloader conflict.  ANyone know?

The code for the classloading hot deploy factory is:

   public static synchronized ResourceRetriever 
createResourceRetriever(ResourceRetriever template) {
     if(resourceClass == null) {
       reloadImpl();
     }
     ResourceRetriever newResourceRetriever = null;
     try {
       newResourceRetriever = (ResourceRetriever)resourceClass.newInstance();
     } catch (InstantiationException ie) {
       LogFactory.getLog(ResourceRetriever.class).error(ie.getMessage());
     } catch (IllegalAccessException iae) {
       LogFactory.getLog(ResourceRetriever.class).error(iae.getMessage());
     }
     return newResourceRetriever;
   }

   public static synchronized void reloadImpl() {
     URL [] serverURLs = null;

     try {
       serverURLs = new URL[] { new URL("file:../hot_deploy/") };
     } catch (java.net.MalformedURLException mue) {
       LogFactory.getLog(ResourceRetriever.class).error(mue.getMessage());
     }

     classLoader = new URLClassLoader(serverURLs);
     try {
       resourceClass = 
classLoader.loadClass("com.michaelmcgrady.resource.ResourceRetrieverImpl");
     } catch (ClassNotFoundException cnfe) {
       LogFactory.getLog(ResourceRetriever.class).error(cnfe.getMessage());
     }

     return;
   }

Thanks.

Michael McGrady



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