App Engine HTTP Status Code message

I found an inconsistency between Java's dev_appserver and the live App Engine server.

On my local development server I have a Servlet which returns:

return response.sendError(response.SC_BAD_REQUEST, "Please log in to comment");

When I access the page I get back a Status Code message in the header which is:

Status Code:400 Please log in to comment

The issue comes when I deploy this to App Engine. When accessing that same servlet I get this "Bad Request" instea开发者_开发技巧d of "Please log in to comment":

Status Code:400 Bad Request

The Please log in to comment Status Code message appears in the content HTML, but not in the header as it does in the development environment.

Why is this?

Edit

Here's the curl -vvvv traces for both dev_appserver and production:

dev_appserver curl trace:

> POST /add-comment HTTP/1.1
> User-Agent: Mozilla/4.0
> Host: localhost:8080
> Accept: */*
> Content-Length: 9
> Content-Type: application/x-www-form-urlencoded
>         
< HTTP/1.1 400 Please log in to comment
< Content-Type: text/html; charset=iso-8859-1
< Cache-Control: must-revalidate,no-cache,no-store
< Content-Length: 1406
< Server: Jetty(6.1.x)

Production curl trace:

> POST /add-comment HTTP/1.1
> User-Agent: Mozilla/4.0
> Host: www.xxx.org
> Accept: */*
> Content-Length: 9
> Content-Type: application/x-www-form-urlencoded
> 
< HTTP/1.1 400 Bad Request
< Content-Type: text/html; charset=utf-8
< Vary: Accept-Encoding
< Date: Thu, 18 Aug 2011 14:04:26 GMT
< Server: Google Frontend
< Cache-Control: private
< Transfer-Encoding: chunked

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I would say the prod system is the correct implementation. The javadocs for sendError() say:

Sends an error response to the client using the specified status. The server defaults to creating the response to look like an HTML-formatted server error page containing the specified message, setting the content type to "text/html", leaving cookies and other headers unmodified. If an error-page declaration has been made for the web application corresponding to the status code passed in, it will be served back in preference to the suggested msg parameter.

If the response has already been committed, this method throws an IllegalStateException. After using this method, the response should be considered to be committed and should not be written to.

I highlighted a part. This says it just returns a html page with the message when possible. It doesn't say it uses it in the HTTP Status code (which I personally haven't seen anywhere as well :()

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It isn't specifically a problem with sendError. The setStatus method will behave the same way. Under normal Java, both sendError and setStatus do set the status description. The issue is that the production App Engine server always sets the status description to the standard description for each code.