Spring Boot | Sample REST Application

In this post we are going to write a Simple REST Application in Spring Boot. Spring Boot has inbuilt tomcat which makes an application start without the need to have any application/web server. Though we can always deploy applications in web servers too.

For this tutorial we will be using Maven for dependency management.

Step 1. Add all required Spring dependencies in your pom file

We can use below sample pom file to start with or go to https://start.spring.io/ to kick start your spring boot application.

	<?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>
	<groupId>com.tutorials.java</groupId>
	<artifactId>SpringBootHelloWorld</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>
	<name>SpringBootDemo</name>
	<description>Spring Boot Demo</description>
	<parent>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-parent</artifactId>
	<version>1.4.0.RELEASE</version>
	<relativePath/>
	</parent>
	<properties>
	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
	<java.version>1.8</java.version>
	</properties>
	<dependencies>
	<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-jpa</artifactId>
	</dependency>
	<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-hateoas</artifactId>
	</dependency>
	<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-jersey</artifactId>
	</dependency>
	<!--<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-security</artifactId>
	</dependency>-->
	<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
	</dependency>
	<dependency>
	<groupId>org.hsqldb</groupId>
	<artifactId>hsqldb</artifactId>
	<scope>runtime</scope>
	</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>

view raw pom.xml hosted with ❤ by GitHub

Step 2. Spring starter class

Spring Boot uses @SpringBootApplication to auto configure some of spring configuration. You can find more info on SpringBoot details

	package com.tutorials.java;
	import org.springframework.boot.SpringApplication;
	import org.springframework.boot.autoconfigure.SpringBootApplication;
	@SpringBootApplication
	public class SpringBootDemoApplication {
	public static void main(String[] args) {
	SpringApplication.run(SpringBootDemoApplication.class, args);
	}
	}

view raw SpringBootDemoApplication.java hosted with ❤ by GitHub

Step 3. Application Controller

We will be using MVC pattern to separate our restful layer from the service layer.  

In our REST service we use @RestController annotation. It is combination of @Controller and @ResponseBody annotations.

We created CustomerController to return customer details.

	package com.tutorials.java.controller;
	import java.util.List;
	import com.tutorials.java.ICustomer;
	import com.tutorials.java.service.CustomerService;
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.web.bind.annotation.PathVariable;
	import org.springframework.web.bind.annotation.RequestMapping;
	import org.springframework.web.bind.annotation.RestController;
	import com.tutorials.java.model.Customer;
	@RestController
	@RequestMapping("/customer")
	public class CustomerController implements ICustomer {
	@Autowired
	private ICustomer customerService;
	@Override
	@RequestMapping
	public List<Customer> getAllCustomers() {
	return customerService.getAllCustomers();
	}
	@Override
	@RequestMapping("/{id}")
	public Customer getCustomerById(@PathVariable String id) {
	return customerService.getCustomerById(id);
	}
	}

view raw CustomerController.java hosted with ❤ by GitHub

Step 4. Application Service 

In any application, the service takes a request from the endpoint and processes it and gives back a response.

In our application we will be returning mocked data for each request. In the real scenario this generally calls any other service (third-party etc), db using a repository to fetch data.

	package com.tutorials.java.service;
	import com.tutorials.java.ICustomer;
	import com.tutorials.java.model.Customer;
	import org.springframework.stereotype.Component;
	import java.util.ArrayList;
	import java.util.List;
	@Component
	public class CustomerService implements ICustomer {
	@Override
	public List<Customer> getAllCustomers() {
	List<Customer> listOfCustomers = new ArrayList();
	Customer rohan = new Customer(1, "Rohan", "Lopes", "abc@abc.com");
	Customer nikhil = new Customer(2, "Nikhil", "Lopes", "xyz@abc.com");
	listOfCustomers.add(rohan);
	listOfCustomers.add(nikhil);
	return listOfCustomers;
	}
	@Override
	public Customer getCustomerById(String id) {
	Customer rohan = new Customer(1, "Rohan", "Lopes", "abc@abc.com");
	return rohan;
	}
	}

view raw CustomerService.java hosted with ❤ by GitHub

Step 5. Disable Spring security

As this is a demo application, we will be disabling the spring authentication. To do that, we will be adding security.basic.enabled=false to the application.properties file.

Step 6. Test Application

Once all changes added we can run command mvn clean install to build our application and create jar file. 

Run this command to start application java -jar target\SpringBootHelloWorld-0.0.1-SNAPSHOT.jar

Project is available on  Git - SpringBootHelloWorld