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)
* Gson [user guide](https://github.com/google/gson/blob/master/UserGuide.md): This guide contains examples on how to use Gson in your code.
* Gson [Roadmap](https://github.com/google/gson/blob/master/ReleaseProcess.md): Details on upcoming releases
* Gson [design document](https://github.com/google/gson/blob/master/GsonDesignDocument.md): This document discusses issues we faced while designing Gson. It also include a comparison of Gson with other Java libraries that can be used for Json conversion
