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JSON

Libraries for using JSON in Java

JSON-simple

http://code.google.com/p/json-simple/
Quite simple to turn a JSON string into an object graph of JSONObject, JSONArray, and Java primitive types.
Using JXPath http://commons.apache.org/jxpath/ you can get at the values held in the ojject graph that JSON-simple returns.

JSON.org

http://www.json.org/java/index.html
You get a bunch of source code classes in the default package which you have to turn into something useful.
But useful it is.
Also quite simple to turn a JSON string into an object graph of JSONObject, JSONArray, and Java primitive types. But you can also convert JSON <==> XML, and other conversions.

google-gson

http://code.google.com/p/google-gson/
More complex, and yet more elegant.
You need to know the schema of your data because, unlike the two examples above, you tell the deserialisor what object type to deserialise the JSON into.
This is similar to unmarshaling XML into objects.

JSON is mentioned on: StartingPoints