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.

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)