I'm using XStream and JETTISON's Stax JSON serializer to send/receive messages to/from JSON javascripts clients and Java web applications.

I want to be able to create a list of objects to send to the server and be properly marshalled into Java but the format that XStream and JSON expect it in is very non-intuitive and requires our javascript libraries to jump through hoops.

[EDIT Update issues using GSON library] I attempted to use the GSON library but it cannot deserialize concrete objects when I only have it expect generic super classes (XStream and Jettison handles this because type information is baked into the serialization).

GSON FAQ states Collection Limitation:

Collections Limitations

Can serialize collection of arbitrary objects but can not deserialize from it

Because there is no way for the user to indicate the type of the resulting object

While deserializing, Collection must be of a specific generic type

Maybe I'm using bad java practices but how would I go about building a JSON to Java messaging framework that sent/received various concrete Message objects in JSON format?

For example this fails:

Here's an example, I want to send a list of 3 Message objects, 2 are of the same type and the 3rd is a different type.

Intuitively I expect the XStream JSON to be serialized (and able to deserialize correctly) from the following format:

Instead XStream creates a single element list with fields that are named the classnames and nested arrays of Objects of the same type.

The trouble may be caused by it using the XStream XML CollectionConverter?

Does anyone have a suggestion for a good JSON Java object serialization that allows you to read/write arbitrary Java objects. I looked at the Jackson Java JSON Processor but when you were reading in objects from a stream you had to specify what type of object it was unlike XStream where it will read in any object (because the serialized XStream JSON contains class name information).