title: How to wrap every Callback in one place to improve error handling
body: <p>Throughout my GWT app there are many different async calls to the server, using many different services. In order to do better error handling I want to wrap all my callbacks so that I can handle exceptions like <code>InvocationExceptions</code> in one place. A super class implementing <code>AsyncCallback</code> isn't really an option because that would mean that I would have to modify every async call.</p>
  
  <p><code>RpcServiceProxy#doCreateRequestCallback()</code> looks like the method to override. Simple enough. I just can't see how to make GWT use my new class.</p>
  
  <p>Another way to state the question would be </p>
  
  <blockquote>
    <p>How do I make GWT use my own subclass of <code>RpcServiceProxy</code>?</p>
  </blockquote>