Subj : Re: Sparodic NoClassDefFoundError: org/mozilla/javascript/optimizer/OptRuntime
To   : netscape.public.mozilla.jseng
From : Igor Bukanov
Date : Fri Jan 21 2005 08:52 pm

redcoat wrote:
> Nope, that still doesn't work!!!!
> 
> Can you remember when this was last reported - we are pretty stuck.
> Any other ideas where to look?

I forgot that adding "synchronized" is not enough as it was necessary to 
add synchronized (parentLoader) as well. Here is the original report:

--------------------------------------------------------------
......
We've had some problems when using Rhino library with Tomcat. We ran 
multiple worker threads on the server side to execute a JavaScript, and 
occasionally but persistently Rhino would throw exceptions like

java.lang.NoClassDefFoundError: org/mozilla/javascript/optimizer/OptRuntime
at org.mozilla.javascript.gen.c3._c0(import)
at org.mozilla.javascript.gen.c3.call(import)
at org.mozilla.javascript.gen.c3.exec(import)

We eventually found that the cause is that Rhino's classloader 
DefiningClassLoader doesn't synchronize the access to its parent loader, 
Tomcat's WebappClassLoader. Once the synchronization is done, no 
exceptions are thrown out.

Now we have two choices

1. Fix Rhino's class loader DefiningClassLoader to synchronize the 
access to the parent loader, or
2. Fix Tomcat's class loader WebappClassLoader.

Do you think that DefiningClassLoader should synchronize the access to 
its parent class loader?
--------------------------------------------------------------

The fix was described later was:

--------------------------------------------------------------
Here is what we did to DefiningClass.java -  we made all methods 
"synchronized" and also synchronized the access to the parent loader in 
method loadClass,

    public synchronized Class loadClass(String name, boolean resolve)
        throws ClassNotFoundException
    {
        Class cl = findLoadedClass(name);
        if (cl == null) {
            if (parentLoader != null) {
              synchronized(parentLoader) {
                cl = parentLoader.loadClass(name);
              }
            } else {
                cl = findSystemClass(name);
            }
        }
        if (resolve) {
            resolveClass(cl);
        }
        return cl;
    }
--------------------------------------------------------------

Regards, Igor

.