title: Intermitant serialization exception with GWT Dev mode and external server
body: <p>I have a GWT app which runs pretty much flawlessly in Dev mode with GWT's embedded jetty server.</p>
  
  <p>However, I need to move over to using an external jetty server (For various reasons). I followed the GWT documentation <a href="http://www.gwtproject.org/doc/latest/DevGuideCompilingAndDebugging.html#How_do_I_use_my_own_server_in_development_mode_instead_of_GWT%27s" rel="nofollow">Compile &amp; Debug</a> for external server setup exactly.</p>
  
  <p>My app runs, however 2/3 of the time on load I get a serialization exception similar to this (On the server side):</p>
  
  <p>com.google.gwt.user.client.rpc.SerializationException: Type 'my.package.impl.ContentTypeImpl' was not assignable to 'com.google.gwt.user.client.rpc.IsSerializable' and did not have a custom field serializer.For security purposes, this type will not be serialized.: instance = my.package.impl.ContentTypeImpl@5e5edf72</p>
  
  <p>I am sure that this particular class is serializable, and I have ensured that I compiled my application and moved the static assets into my external servers war directory. Like I said, it works about every third time I refresh the browser.</p>
  
  <p>Any suggestions?</p>
  
  <p>Thanks!</p>