I have a GWT application that needs to support the downloading of large .csv files. This is done with a ReportServlet which sets the proper content-type and other headers needed for the browser to open the download dialog and start the spreadsheet application.

Since the reports have several filter parameters, I need to pass them to the server somehow. I can not use AJAX callbacks because in that case the browser does not pop up the download dialog. 
Currently I am doing this by creating a form with hidden fields for each parameter and parse them each at the server side by hand.

It would be a much more elegant solution to have a serializer for the value object, put the serialized value in *one* form parameter, deserialize on the server and use it as we were in a regular RPC call.

At first I tried to search the GWT codebase for some serializer/deserializer api but I could not find any. After that I searched for JSON serializers but non of them had either a simple API or support for GWT. These two JSON serializers:
<http://code.google.com/p/gwtprojsonserializer/> and <http://sites.google.com/site/gson/>
could be great, but gwtprojson serializes Dates as timestamps and put the classname in the serialized string while gson as a dateformat string and no classname in the serialized string.

**So to finally get to the point**

Could anyone suggest an object serializer/deserializer that works both in GWT and java? Not neccessarily JSON, any other format will do.  

or  

Has anyone experience with using the serializer libraries mentioned above together, or with other libs that can serialize in GWT and deserialize in Java?

Thanks in advance!
pentike