Microservices: The Spring Boot Way

Some Food for Thought

When a Java developer thinks of developing a web application/services in Java and what it involves, the following list likely comes to mind:

• Servlet APIs
• Web Frameworks (Struts/SpringMVC/REST API frameworks etc)
• Application Logic
• Web Container (Tomcat/JBoss)
• Build Scripts (ANT/MAVEN)
• Deployment    

Now compare this with what comes to our mind when we think of developing a standalone Java program/application:

• Application Logic

That's it!

This exactly what Spring Boot tries to achieve. It makes writing a web application as easy as writing a standalone application with almost zero boilerplate code! All you need to worry about is your Application logic and leave rest to Spring Boot! 

Here is how to do it. 

Prerequisite: JDK 1.7 or above, Maven 3.x, and IDE or your choice. 

Step 1: Download Spring Boot. The easiest way is to do it using Maven. Create a basic JAR project in Maven. From the command prompt execute the following:

mvn archetype:create -DgroupId=com.springboot -DartifactId=spring-boot-example

This will create a standalone JAR project. Open its  pom.xml file. 

Step 2: Add the following dependencies:

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.3.RELEASE</version>
</parent>
<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
</dependencies>

Step 3: Now create the following class:

package com.springboot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;


@RestController
@EnableAutoConfiguration
public class SampleController {

    @RequestMapping("/")
    String home() {
        return "Hello World!";
    }

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

This is a simple RESTful service which when requested via GET, returns Hello World. And this is all you need as far as writing code is concerned, the surprise continues.  

Step 4: Compile the project:

mvn compile

Step 5: Now it's time to run. There are many ways this can be run, but the easiest way when using Maven is using this plugin. So add the exec-maven-plugin plugin to pom.xml :

    <plugins>
        <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.0.2</version>
            <configuration>
                <source>1.7</source>
                <target>1.7</target>
            </configuration>
         </plugin>
         <plugin>
             <groupId>org.codehaus.mojo</groupId>
             <artifactId>exec-maven-plugin</artifactId>
             <configuration>
                 <mainClass>com.springboot.SampleController</mainClass>
             </configuration>
        </plugin>
    </plugins>
</build>

Step 6: After this, running is as easy as:

mvn exec:java

It starts and prints a lot of messages; in the end you will see something like this:

2016-04-09 21:11:19.574  INFO 10384 --- [ntroller.main()] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2016-04-09 21:11:19.581  INFO 10384 --- [ntroller.main()] com.springboot.SampleController          : Started SampleController in 9.939 seconds (JVM running for 19.084)

This indicates that the service is up and running. 

Step 7: Now that the service is up and running, it's time to test the service. Point your browser to http://localhost:8080, and you should see "Hello world!"

So, your service is ready to be used! No creation of WARs and no deployment in Tomcat. 

Well, all this is done, and as a developer I am happy that it saved me a lot of effort, but as a good developer, I should know how it's happening behind the scene. 

What Spring Boot does for you is:

• Looks at your classpath and at beans you have configured.
• Makes reasonable assumptions about what you’re missing, and adds it. For example, when it sees@RestController it knows you are going to need Tomcat and it adds the embedded Tomcat.
• It does everything around starting the code and deploying the application.
• It reads all the annotations and creates the mappings of request paths and method to be executed.

Spring Boot offers a fast way to build microservces-based applications. With Spring Boot you can focus more on business features and less on infrastructure (framework, deployment, web server, etc.).