GSON - First Application

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Before going into the details of the Google Gson library, let's see an application in action. In this example, we've created a Student class. We'll create a JSON string with student details and deserialize it to student object and then serialize it to an JSON String.

Example - Serialize/Deserialize Student Object using JSON

GsonTester.java

 package com.tutorialspoint; import com.google.gson.Gson; import com.google.gson.GsonBuilder; public class GsonTester { public static void main(String[] args) { String jsonString = "{\"name\":\"Mahesh\", \"age\":21}"; GsonBuilder builder = new GsonBuilder(); builder.setPrettyPrinting(); Gson gson = builder.create(); Student student = gson.fromJson(jsonString, Student.class); System.out.println(student); jsonString = gson.toJson(student); System.out.println(jsonString); } } class Student { private String name; private int age; public Student(){} public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String toString() { return "Student [ name: "+name+", age: "+ age+ " ]"; } } 

Output

Run the GsonTester and verify the output.

 Student [ name: Mahesh, age: 21 ] { "name" : "Mahesh", "age" : 21 } 

Steps to Remember

Following are the important steps to be considered here.

Step 1 − Create Gson object using GsonBuilder

Create a Gson object. It is a reusable object.

 GsonBuilder builder = new GsonBuilder(); builder.setPrettyPrinting(); Gson gson = builder.create(); 

Step 2 − Deserialize JSON to Object

Use fromJson() method to get the Object from the JSON. Pass Json string / source of Json string and object type as parameter.

 //Object to JSON Conversion Student student = gson.fromJson(jsonString, Student.class); 

Step 3 − Serialize Object to JSON

Use toJson() method to get the JSON string representation of an object.

 //Object to JSON Conversion jsonString = gson.toJson(student);