JSON serialization with Jackson in Spring Boot - Mini Project: Build & Apply

JSON serialization with Jackson

📖 Scenario: You are building a simple Spring Boot application that sends user information as JSON data over the web.Jackson is the tool that converts your Java objects into JSON format automatically.

🎯 Goal: Create a Java class representing a user, configure Jackson to serialize it, and produce JSON output with selected fields.

📋 What You'll Learn

Create a Java class called User with fields id, name, and email

Add a configuration variable to control if the email field is included in JSON

Use Jackson annotations to include or exclude the email field based on the configuration

Create a Spring Boot REST controller that returns a User object as JSON

💡 Why This Matters

🌍 Real World

APIs often send data as JSON. Jackson helps convert Java objects to JSON easily.

💼 Career

Understanding JSON serialization with Jackson is essential for backend developers working with Spring Boot APIs.

1

Create the User class with fields

Create a Java class called User with private fields int id, String name, and String email. Add a constructor that takes all three fields and getters for each field.

Spring Boot

public class User {
    // Your code here
}

Need a hint?

Define private fields and create a constructor and getters for each field.

2

Add a configuration variable to control email inclusion

Add a public static boolean variable called includeEmail in the User class and set it to true.

Spring Boot

public class User {
    private int id;
    private String name;
    private String email;

    public static boolean includeEmail = true;

    // Your code here
}

Need a hint?

Add a static boolean variable named includeEmail and set it to true.

3

Use Jackson annotation to conditionally include email

Add the Jackson annotation @JsonInclude with JsonInclude.Include.NON_NULL to the getEmail() method. Modify getEmail() to return email if includeEmail is true, otherwise return null.

Spring Boot

import com.fasterxml.jackson.annotation.JsonInclude;

public class User {
    private int id;
    private String name;
    private String email;

    public static boolean includeEmail = true;

    public User(int id, String name, String email) {
        this.id = id;
        this.name = name;
        this.email = email;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    @JsonInclude(JsonInclude.Include.NON_NULL)
    public String getEmail() {
        // Your code here
    }
}

Need a hint?

Use @JsonInclude(JsonInclude.Include.NON_NULL) on getEmail() and return email only if includeEmail is true, else return null.

4

Create a REST controller to return User as JSON

Create a Spring Boot REST controller class called UserController with a method getUser() mapped to /user that returns a new User object with id=1, name="Alice", and email="[e-mail]".

Spring Boot

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {
    // Your code here
}

Need a hint?

Create a class annotated with @RestController. Add a method getUser() with @GetMapping("/user") that returns a new User object.