JPype

I also ran into this problem, so I did a little digging and found that it
was related to current class limitation documented in the the JPype user
manual. I don't know what needs to be done to fix it, but in the meantime,
an easy workaround is to write a Java class that extends the
ObjectInputStream class and overrides the resolveClass method, so that it
uses the System class loader. Then, you can use this new class wherever
you would use the ObjectInputStream class and things load without any
problem. So, more specifically, I wrote the following class and
substituted it for the built-in ObjectInputStream class:

package com.adverplex.captcha;

import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.io.IOException;

public class JPypeObjectInputStream extends ObjectInputStream {

public JPypeObjectInputStream(InputStream in) throws IOException
{
super(in);
}

protected Class<?> resolveClass(ObjectStreamClass desc) throws
IOException, ClassNotFoundException
{
return Class.forName(desc.getName(), true,
ClassLoader.getSystemClassLoader());
}
}