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.

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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.

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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