Try this serializer from Google Code: http://code.google.com/p/json-io/
If you need to write or read JSON format in Java, this is the tool to use. No need to create extra classes, etc. Convert a Java object graph to JSON format in one call. Do the opposite - create a JSON String or Stream to Java objects. This is the fastest library I have seen yet to do this. It is faster than ObjectOutputStream and ObjectInputStream in most cases, which use binary format.
Very handy utility.