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.

https://github.com/google/gson/blob/master/UserGuide.md

Maven

 <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.5</version>
      <scope>compile</scope>
    </dependency>

@Expose annotation

To use this annotation, you must create Gson by using new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create(). The Gson instance created will exclude all fields in a class that are not marked with @Expose annotation.

http://google.github.io/gson/apidocs/com/google/gson/annotations/Expose.html
GSON gson = new GsonBuilder.excludeFieldsWithoutExposeAnnotation().create()

@SerializedName annotation

Sets the field name in the serialzied JSON.

http://google.github.io/gson/apidocs/com/google/gson/annotations/SerializedName.html