SECURITY INTERNAL . COM: A Quick Start Guide for Writing Microservices with Spring Boot

Microservices architectural style is an approach to developing a single application as a suite of small services, each running in its own process. In this approach, instead of writing a monolithic application, we implement the same functionality by breaking it down to a set of lightweight services.

There are various frameworks that provide capability of writing microservices and in this post, I’m discussing how to do it using Spring Boot https://projects.spring.io/spring-boot/ .

I’m going to create an API for handling user operations and expose the operations as RESTful services. The service context is /api/user and based on the type of the HTTP request, appropriate operation will be decided. (I could have further divided this to four microservices... but let’s create them as one for the moment)

Let’s get started with the implementation now. I simply create a Maven project (java) with the following structure.

└── UserAPI_Microservice

├── pom.xml

├── src

│ ├── main

│ │ └── java

│ │ └── microservice

│ │ ├── App.java

│ │ └── UserAPI.java

Add following parent and dependency to the pom.xml file of the project.

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-parent</artifactId>

<version>1.4.3.RELEASE</version>

</parent>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-web</artifactId>

</dependency>

The App class has the main method which runs the UserAPI.

package com.tharindue;

import org.springframework.boot.SpringApplication;

public class App {

public static void main(String[] args) throws Exception {

SpringApplication.run(UserAPI.class, args);

}

The UserAPI class exposes the methods in the API. I have defined the context api/user at class level and for the methods, I haven’t defined a path, but only the HTTP request type.

package com.tharindue;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

import org.springframework.stereotype.Controller;

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

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.ResponseBody;

@Controller

@EnableAutoConfiguration

@RequestMapping("api/user")

public class UserAPI {

@RequestMapping(method = RequestMethod.GET)

@ResponseBody

String list() {

return "Listing User\n";

}

@RequestMapping(method = RequestMethod.POST)

@ResponseBody

String add() {

return "User Added\n";

}

@RequestMapping(method = RequestMethod.PUT)

@ResponseBody

String update() {

return "User Updated\n";

}

@RequestMapping(method = RequestMethod.DELETE)

@ResponseBody

String delete() {

return "User Deleted\n";

}

After building the project with maven, simple run the below command and the service will start serving in the 8080 port of localhost.

mvn spring-boot:run

If you need to change the port of the service, use the following command. (here instead of 8081, you can add the port number you wish).

mvn spring-boot:run -Drun.jvmArguments='-Dserver.port=8081'

You can also run the microservice with the “java -jar <file name>” command, provided that the following plugin is added to the pom.xml file. You need to specify the mainClass value pointing to the class where you have the main method. This will re-package the project and the jar file will contain the dependencies as well. When you run the jar file, the service will be started in the default port which is 8080. If you want to change the default port, run the command “java -jar <file name> --server.port=<port number>”

<build>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-maven-plugin</artifactId>

<mainClass>com.tharindue.App</mainClass>

</configuration>

<goals>

<goal>repackage</goal>

</goals>

</execution>

</executions>

</plugin>

</plugins>

</build>

In my case, the service starts in 1.904 seconds. It’s a pretty good speed comparing the hassle you have to go through building a war file and then deploying it in an app service like tomcat.