title: How to intercept the onSuccess() method in GWT
body: <p>I need to do method interception for the <code>onSuccess</code> method in GWT.</p>
  
  <p>I need to add some code <strong>before</strong> and <strong>after</strong> the calling of the onSuccess method in GWT? (I have many calls to the onSuccess method and I need to do this dynamically)</p>
  
  <p><strong>EDIT:</strong>
  I need to add a <code>progress bar</code> in the right corner of the screen, that appears when the code enters the <code>onsuccess</code> method and disappears on the exit of <code>onsuccess</code> method.</p>