Spring Boot @ResponseBody - Creating Controller Return Values to Response Body

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In this short article, we will learn how to use Spring Boot @ResponseBody annotation in a controller to write data to the body of the response object. We create a Spring Boot RESTful application to demonstrate the annotation.

Spring @ResponseBody

@ResponseBody is a Spring annotation which binds a method return value to the web response body. It is not interpreted as a view name. It uses HTTP Message converters to convert the return value to HTTP response body, based on the content-type in the request HTTP header.
Here is a sample code snippet:
    @ResponseBody
    @GetMapping(path = "/users")
    public List<User> home() {
        return Arrays.asList(new User(1, "Ramesh"), 
          new User(2, "Prabhas"), 
          new User(3, "John"),
          new User(4, "Tony"),
          new User(4, "Tom"));
    }

Spring Boot @ResponseBody Annotation Example

The following example creates a Spring Boot web application that returns JSON data to the client.

Development Steps

  1. Create a Spring Boot Application
  2. Project Structure
  3. Pom Dependencies
  4. Java Bean - User.java
  5. Create REST Controller - UserController.java
  6. Run Application - Application.java

1. Create a Spring Boot Application

There are many ways to create a Spring Boot application. You can refer below articles to create a Spring Boot application.
Refer project structure or packaging structure in the next step.

2. Project Structure

This is the project structure of the Spring Boot application that we are going to create - 

3. Pom Dependencies

This is the Maven build file. The spring-boot-starter-web is a starter for building web applications using Spring MVC. It uses Tomcat as the default embedded container.
<?xml version="1.0" encoding="UTF-8"?>
<project
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
        <relativePath />
        <!-- lookup parent from repository -->
    </parent>
    <groupId>net.javaguides.springboot</groupId>
    <artifactId>springboot-annotations-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-annotations-demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

4. Java Bean - User.java

Let's create a representation class which we use to return in JSON format:
package net.javaguides.springboot;

public class User {

    private Integer id;
    private String name;

    public User() {}

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

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

5. Create REST Controller - UserController.java

Let's create a simple UserController with users rest API which returns a list of users in JSON format.
package net.javaguides.springboot;

import java.util.Arrays;
import java.util.List;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class UserController {

    @ResponseBody
    @GetMapping(path = "/users")
    public List
        <
        User > home() {
            return Arrays.asList(new User(1, "Ramesh"),
                new User(2, "Prabhas"),
                new User(3, "John"),
                new User(4, "Tony"),
                new User(4, "Tom"));
        }
}

6. Run Application - Application.java

Application is the entry point that sets up the Spring Boot application. The @SpringBootApplication annotation enables auto-configuration and component scanning.
Let's run this Spring boot application from either Eclipse IDE by right click - Run As - Java Application.
Or you can use the below maven command to run:
mvn spring-boot:run

7. Testing from Browser

Hit this URL in a browser - http://localhost:8080/users

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