How to Make a Simple RestController in Spring Boot?

In Spring Boot, a RestController is used to create RESTful web services that return JSON or XML responses. It combines the functionality of @Controller and @ResponseBody, making it easy to handle HTTP requests and send responses without writing boilerplate code.

• @RestController eliminates the need to annotate each method with @ResponseBody.
• It is ideal for building APIs for web or mobile applications.

Steps to Create a Simple RestController in Spring Boot

Step 1: Create a New Spring Boot Maven Project

• Open IntelliJ IDEA.
• Click on New Project.
• Select Spring Initializr and click Next.
• Enter the project details:
• Group Id: com.geeksforgeeks
• Artifact Id: springboot-restcontroller
• Project Type: Maven
• Packaging: jar
• Java Version: 17
• Click Next.
• Select the required dependency:
• Spring Web
• Click Finish to create the project.

After completing these steps, IntelliJ IDEA will generate a Spring Boot Maven project with all required configurations.

Step 2: Project Structure

Step 3: Add pom.xml

Here is the pom.xml for your project:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="https://maven.apache.org/POM/4.0.0"
         xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 
                             https://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>3.4.4</version>
        <relativePath/>
    </parent>

    <groupId>com.geeksforgeeks</groupId>
    <artifactId>restcontroller-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>restcontroller-demo</name>

    <properties>
        <java.version>17</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>

Step 4: Create SpringBootApplication Class

Create SpringBootApplication.java inside src/main/java/com/geeksforgeeks/SpringBootApplication/:

package com.geeksforgeeks.SpringBootApplication;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootApplicationDemo {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootApplicationDemo.class, args);
    }
}

Step 5: Create a Simple RestController

Create Controller.java inside src/main/java/com/geeksforgeeks/SpringBootApplication/controller/:

package com.geeksforgeeks.springbootapplication;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootRestApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootRestApplication.class, args);
    }
}

Explanation:

• @RestController -> Marks this class as a RESTful controller.
• @RequestMapping("/api") -> Sets the base URL for all endpoints.
• @GetMapping("/hello/{name}/{age}") -> Handles HTTP GET requests and captures name and age from the URL.
• The method returns a JSON string as a response.

Step 6: Run the Spring Boot Application

• Open SpringBootApplicationDemo.java
• Right-click -> Run as Java Application
• Wait for the Spring Boot app to start on port 8080

Tip: Change the port in application.properties if needed.

Step 7: Test the API

• Open a browser or Postman
• Test the URL: http://localhost:8080/api/hello/Kadrun/24

Output: