Why ObjectInputStreamWithClassLoader overrides resolveClass method?

[gaohoward]

Hi,

I'm trying to understand class ObjectInputStreamWithClassLoader's method resolveClass(). In that method, it tries to use the thread context classloader to load the class, as opposed to it's super method

   protected Class resolveClass(final ObjectStreamClass desc) throws IOException, ClassNotFoundException
   {
      String name = desc.getName();
      ClassLoader loader = Thread.currentThread().getContextClassLoader();
      try
      {
         Class clazz = loader.loadClass(name);
         // sanity check only.. if a classLoader can't find a clazz, it will throw an exception
         if (clazz == null)
         {
            return super.resolveClass(desc);
         }
         else
         {
            return clazz;
         }
      }
      catch (ClassNotFoundException e)
      {
         return super.resolveClass(desc);
      }

My question is why does it so implemented? What's wrong if we just use the super method?

Thanks

[clebert.suconic]

ObjectInputStream doesn't define any way to override the classLoader.

Say the user is doing objMessage.getObject() from a MDB. The class may be only defined at the EAR's classLoader, and its classLoader is accessed through the ContextClassLoader on the Thread.

ObjectInputStream would only look for objects at the classPath (or root classLoader).  So, we needed to implement the feature.

We need to do it to couple with Application Server's classLoading.

[clebert.suconic]

Also, if it can't find it on that Thread Context Class Loader (TCCL) it will look at the super method which will look at the root classLoader (classPath)