Spring Boot REST API That Returns JSON

In this guide, we will build the Spring Boot REST API that returns a Java Bean in JSON format. This is a common requirement for building web services that return the JSON to the client.

Learn everything about Spring Boot: Spring Boot Tutorial.

Setting Up the Project

Using Spring Initializr

Open Spring Initializr:

• Navigate to Spring Initializr in your web browser.

Configure Project Metadata:

• Group: com.company
• Artifact: springboot-rest-api
• Name: springboot-rest-api
• Description: Spring Boot REST API returns Java Bean as JSON
• Package name: com.company.restapi
• Packaging: Jar
• Java Version: 21 (or the latest version available)
• Spring Boot Version: Select the latest version of Spring Boot

Select Dependencies:

• Spring Web

Generate and Download:

• Click the “Generate” button to download the project as a ZIP file.

Importing the Project into IntelliJ IDEA

Open IntelliJ IDEA:

• Launch IntelliJ IDEA from your installed applications.

Import the Project:

• On the welcome screen, click “Open or Import”.
• Navigate to the directory where you downloaded the Spring Initializr ZIP file.
• Select the ZIP file and click “Open”.
• IntelliJ IDEA will unzip the file and import the project.

Configure Maven (if needed):

• IntelliJ IDEA will automatically detect the Maven build file (pom.xml) and import the project.
• If prompted, confirm any necessary Maven configurations.

Step 1: Create a Java Bean

Create a new package:

• In the src/main/java/com/company/restapi directory, create a new package named model.

Create the Java Bean:

• Inside the model package, create a new class named Student.
• Add the following code to the Student class:

package com.company.restapi.model;

public class Student {
    private Long id;
    private String firstName;
    private String lastName;
    private String email;

    // Constructors
    public Student() {}

    public Student(Long id, String firstName, String lastName, String email) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.email = email;
    }

    // Getters and Setters
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

Explaining the Java Bean

• Fields: The Student class has four fields: id, firstName, lastName, and email.
• Constructors: The class includes a no-argument constructor and a parameterized constructor.
• Getters and Setters: The class provides getter and setter methods for each field, allowing other classes to access and modify the values.

Step 2: Create a Controller Class

Create a new package:

• In the src/main/java/com/company/restapi directory, create a new package named controller.

Create the Controller Class:

• Inside the controller package, create a new class named StudentController.
• Add the following code to the StudentController class:

package com.company.restapi.controller;

import com.company.restapi.model.Student;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class StudentController {

    @GetMapping("/student")
    public Student getStudent() {
        return new Student(1L, "Ramesh", "Fadatare", "ramesh.fadatare@example.com");
    }
}

Explaining the Controller Class

• @RestController Annotation: Marks the class as a Spring MVC controller where every method returns a domain object instead of a view. It is a convenience annotation that combines @Controller and @ResponseBody.
• @GetMapping("/student") Annotation: Maps HTTP GET requests to the /student URL to the getStudent method.
• getStudent Method: Returns a new Student object with sample data.

Step 3: Run Your Spring Boot Application

Open Application Class:

• Navigate to the main application class (annotated with @SpringBootApplication).

Run the Application:

• In IntelliJ IDEA, right-click the main application class and select “Run ‘SpringbootRestApiApplication’”.
• Alternatively, open a terminal, navigate to the project directory, and run mvn spring-boot:run.

Verify the Application:

• Open a web browser and go to http://localhost:8080/student.
• You should see a JSON representation of the Student object:

{
    "id": 1,
    "firstName": "Ramesh",
    "lastName": "Fadatare",
    "email": "ramesh.fadatare@example.com"
}

Output

Conclusion

In this guide, we have created a simple Spring Boot REST API that returns a Java Bean as JSON. We set up the project, created a Student Java Bean, developed a REST API and ran the application to verify the JSON output. This example provides a foundation for building more complex REST APIs with Spring Boot.

Learn everything about Spring Boot: Spring Boot Tutorial.