What client artifacts are thread safe?
javax.xml.rpc.ServiceFactory - Just a factory so yes it is thread safe.
javax.xml.rpc.Service - A factory for calls and stubs so it is thread safe.
javax.xml.rpc.Call - Not thread safe, the API allows for multiple method invocations for a single WS call.
javax.xml.rpc.Stub - Contains properties that may be thread specific. Stub is the interface implemented by the dynamic proxy which delegates
to an implementation of Call. So, whatever is true for Call also holds for the dynamic proxy implementing Stub.