For a web-application I once created a web service proxy to communicate with a web service. In this same application we also communicated with BPEL by using the HumanWorkflow API. Why this is important to know I will explain later.
Creating the proxy was a really simple thing to do with JDeveloper 10.1.3. Just run the wizard and select the corresponding WSDL and voila. I had done this many times with JDev 10.1.2. but this time the generated webservice proxy gave compile errors! And I had done nothing exotic whatsoever!

The error was in the constructor of the class 'MyWebService1SoapHttpPortClient':

PLAIN TEXT
JAVA:
  1. public MyWebService1SoapHttpPortClient() throws Exception
  2. {
  3.   ServiceFactory factory = ServiceFactory.newInstance();
  4.   _port =
  5.  ((test.ws.MyWebService1_Service)factory.loadService(test.ws.MyWebService1_Service.class)).getMyWebService1SoapHttpPort();
  6. }

Of course I didn't give the service really that name. This is just an example.

The error said:
Error(22,57): method loadService(java.lang.Class) not found in class javax.xml.rpc.ServiceFactory

After some extensive search I found out the error was caused by the loaded libraries in the project. Apparently the library needed for communication with the BPEL Workflow API 'BPM Workflow' loaded some old classes that were interfering with the generated proxy classes. The issue was solved by moving the 'BPM Workflow' library downwards, so it is loaded after the ' JAX-RPC Client'.

loaded_libraries

By doing this the generated proxy compiled (and worked) fine.

Later on the development of the web-application I decided to split the functionality in different project so this issue wasn't a problem anymore, but if you are running into the same issue maybe this post will help you.