AppEngine with Restlet handling requests, NullPointEerexception with DomRepresentation response

After deploying my App Engine app and doing a POST request that is supposed to return XML, I get the following error:

org.restlet.engine.http.HttpServerAdapter commit: An exception occured writing t开发者_如何学编程he response entity
java.io.IOException: Couldn't write the XML representation: java.lang.NullPointerException
    at org.restlet.ext.xml.DomRepresentation.write(DomRepresentation.java:275)
    at org.restlet.engine.http.HttpServerCall.writeResponseBody(HttpServerCall.java:510)

Doing the exact same request on the app ran locally does not cause any errors.

Maybe you have data in your local db, that is not accessible in the deployed version? Please give some more background information (code, libraries), if that is not it.

This is due to a GAE issue with chunked encoding. There is now a workaround in Restlet 2.1 M3. See the related question: Restlet POSTing JSON to Appengine error