wsdl2java and java.util.Set

[Nikita Tovstoles]

I'm using wsdl2java to generate client-side ws stubs using JDK 1.5.  One 
of my javabeans contains java.util.Set property (needed for Hibernate). 
The generated binding stub class contains the following related code:

qName = new 
javax.xml.namespace.QName("http://java.sun.com/jax-rpc-ri/internal";, "set");
           cachedSerQNames.add(qName);
           cls = com.sun.java.jax_rpc_ri.internal.Set.class;
           cachedSerClasses.add(cls);
           cachedSerFactories.add(beansf);
           cachedDeserFactories.add(beandf);
Problem is, com.sun.java.jax_rpc_ri.internal.* is nowhere to be found. 
Where can I find that package?
I read JAX-RPC documentation, and it states that java.util.Set is a 
supported type. Why the need for this cls at all?

thanks,
-nikita