Spring Boot – Creating a RESTful Web Service Example

In the previous article we have just created a simple hello world spring boot application, in this tutorial I am going to show you how to create a Restful web service using Spring Boot, believe me its very simple 🙂

Lets start with the directory structure of the project. (if you want to know how to create a simple spring boot project, you can go back to the previous article Spring Boot + Maven – Hello World Example Step by Step)

Directory Structure

 Required files

• SpringBootApp.java
• SpringJava4sController.java
• pom.xml

pom.xml

<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>
  <groupId>com.java4s</groupId>
  <artifactId>SpringBootHelloWorld</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  	 <parent>
	    <groupId>org.springframework.boot</groupId>
	    <artifactId>spring-boot-starter-parent</artifactId>
	    <version>1.5.6.RELEASE</version>
	</parent>
	
	<dependencies>
	    <dependency>
	        <groupId>org.springframework.boot</groupId>
	        <artifactId>spring-boot-starter-web</artifactId>
	    </dependency>
	</dependencies>
	
	<properties>
	 <java.version>1.8</java.version>
	</properties> 
  
</project>

SpringBootApp.java

package com.java4s.app;

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

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

SpringJava4sController.java

package com.java4s.app.controller;

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

@RestController
public class SpringJava4sController {

	@RequestMapping("/")
	public String welcome() {
		return "Welcome to Spring Boot Tutorials";
	}
	
	@RequestMapping("/hello")
	public String myData() {
		return "Hello Spring Boot";
	}
}

Explanation

Friends, I took previous spring boot hello world application and just added the SpringJava4sController class and written RESTful web service related logic. I haven’t added any new dependencies nor written any XML’s, rather added a simple java class. My REST class is annotated with @RestController, which tells Spring Boot to consider this class as REST controller and register @RequestMapping paths inside it to respond to the HTTP requests.

Note: Spring Boot will use 8080 as default tomcat port

Run the application and hit http://localhost:8080  [ This is for @RequestMapping(“/”) ]

Now try hitting  http://localhost:8080/hello   [ This is for @RequestMapping(“/hello”) ]

Note:  Have you clearly observed the above directory structure? I have created Spring Boot main application class in com.java4s.app and controller class in com.java4s.app.controller, and in my controller class I have written my RESTful service logic and was able to execute the application successfully. How spring boot knows to scan our controller? As we have created our main class in com.java4s.app package, while starting our application, it will scan all the components under that package.  As we have created our controller class in com.java4s.app.controller which is inside com.java4s.app, our controller was registered by spring boot.

If you create the controller class outside of the main package, lets say com.java4s.controller, If you run the application it gives 404 error, just give a try and see 🙂

What’s the solution for this?  we have to add @ComponentScan annotation in our Spring Boot main class, something like this..

package com.java4s.app;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan(basePackages="com.java4s.controller")
public class SpringBootApp {
	public static void main(String[] args){
		 ---
	}
}

That’s it friends, hope you enjoyed this article 🙂

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::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.