Gson – Overview

Google Gson is a simple Java-based library to serialize Java
objects to JSON and vice versa. It is an open-source library
developed by Google.

The following points highlight why you should be using this
library −

• Standardized − Gson is a standardized library that is
  managed by Google.
• Efficient − It is a reliable, fast, and efficient
  extension to the Java standard library.
• Optimized − The library is highly optimized.
• Support Generics − It provides extensive support for
  generics.
• Supports complex inner classes − It supports complex
  objects with deep inheritance hierarchies.

Features of Gson

Here is a list of some of the most prominent features of Gson −

• Easy to use − Gson API provides a high-level facade to
  simplify commonly used use-cases.
• No need to create mapping − Gson API provides default
  mapping for most of the objects to be serialized.
• Performance − Gson is quite fast and is of low memory
  footprint. It is suitable for large object graphs or systems.
• Clean JSON − Gson creates a clean and compact JSON
  result which is easy to read.
• No Dependency − Gson library does not require any
  other library apart from JDK.
• Open Source − Gson library is open source; it is
  freely available.

Three Ways of Processing JSON

Gson provides three alternative ways to process JSON −

Streaming API

It reads and writes JSON content as discrete events.
JsonReader and JsonWriter read/write the data as
token, referred as JsonToken.

It is the most powerful approach among the three approaches to
process JSON. It has the lowest overhead and it is quite fast in
read/write operations. It is analogous to Stax parser for XML.

Tree Model

It prepares an in-memory tree representation of the JSON
document. It builds a tree of JsonObject nodes. It is a flexible
approach and is analogous to DOM parser for XML.

Data Binding

It converts JSON to and from POJO (Plain Old Java Object) using
property accessor. Gson reads/writes JSON using data type
adapters. It is analogous to JAXB parser for XML.