For the Java code to lookup the third party classes at runtime, set ContextClassLoader as follows:
ClassLoader cl = null;
cl = Thread.currentThread().getContextClassLoader();
try
{
Thread.currentThread().setContextClassLoader(getClass().getClassLoader());
.....Your Java Code calling the third party library.....
} finally {
Thread.currentThread().setContextClassLoader(cl);
}
There is a sample shipped with product showing the usecase : Interoperability of Using JAX-WS Client to Invoke Service (tibco.bw.sample.binding.soap.http.JAXWSInterop).