How to use GSON for Java serialization?

How to use GSON for Java serialization? Install the GSON library. Serialize an object: Convert the object to a JSON string using the toJson() method. Deserialize JSON: Use the fromJson() method to restore an object from a JSON string. Practical example: Using GSON to serialize Java objects in a REST API and return a JSON response.

How to use GSON for Java serialization

Introduction

GSON (Google JSON) is a Java library for serializing objects to and deserializing objects from JSON. It's easy to use, fast, and supports a wide range of data types.

Install GSON

Add GSON to your project via Maven:

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.10.1</version>
</dependency>

Serialized objects

To serialize an object to JSON, use toJson() Method:

import com.google.gson.Gson;

public class Main {
  public static void main(String[] args) {
    User user = new User("John Doe", 30);
    Gson gson = new Gson();
    String json = gson.toJson(user);
    System.out.println(json);
  }
  
  static class User {
    private String name;
    private int age;
    
    public User(String name, int age) {
      this.name = name;
      this.age = age;
    }
  }
}

Output:

{"name":"John Doe","age":30}

Deserialize JSON

To deserialize an object from JSON, use fromJson() Method:

import com.google.gson.Gson;

public class Main {
  public static void main(String[] args) {
    String json = "{\"name\":\"John Doe\",\"age\":30}";
    Gson gson = new Gson();
    User user = gson.fromJson(json, User.class);
    System.out.println(user.getName());
  }
  
  static class User {
    private String name;
    private int age;
    
    public User(String name, int age) {
      this.name = name;
      this.age = age;
    }
    
    public String getName() {
      return name;
    }
  }
}

Output:

John Doe

Practical case

Suppose you are building a REST API and need to return Java objects as JSON responses. Using GSON, you can implement serialization like this:

import com.google.gson.Gson;

@RestController
@RequestMapping("/api/users")
public class UserController {
  
  @GetMapping
  public List<User> getUsers() {
    Gson gson = new Gson();
    List<User> users = // Fetch a list of users from the database;
    String json = gson.toJson(users);
    return ResponseEntity.ok(json)
                       .addHeader("Content-Type", "application/json");
  }
  
  static class User {
    // Define the User model
  }
}

This way, the controller can return a serialized JSON response that can be easily parsed by a front-end application or other client.

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