google-gson - A Java library to convert JSON to Java objects and vice-versa

http://code.google.com/p/google-gson/

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

There are a few open-source projects that can convert Java objects to JSON. However, most of them require that you place Java annotations in your classes; something that you can not do if you do not have access to the source-code. Most also do not fully support the use of Java Generics. Gson considers both of these as very important design goals.

Gson Goals

Provide simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa

Allow pre-existing unmodifiable objects to be converted to and from JSON

Extensive support of Java Generics

Allow custom representations for objects

Support arbitrarily complex objects (with deep inheritance hierarchies and extensive use of generic types)