Creating Simple Java Microservice

Last Updated: March 26, 2021

This section shows how to create a simple REST Microservice service based on Java Jackson and Jersy API’s in no-time.

Steps:

Create Maven project with the following 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.jalalkiswani.examples</groupId>
	<artifactId>smart-cloud-microservice-example</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
	<properties>
		<smart-cloud.version>4.0.8</smart-cloud.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>com.jalalkiswani</groupId>
			<artifactId>smart-cloud-standalone</artifactId>
			<version>${smart-cloud.version}</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>com.jalalkiswani</groupId>
			<artifactId>smart-cloud-web</artifactId>
			<version>${smart-cloud.version}</version>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.8.1</version>
				<configuration>
					<!-- http://maven.apache.org/plugins/maven-compiler-plugin/ -->
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-war-plugin</artifactId>
				<version>3.2.3</version>
				<configuration>
					<failOnMissingWebXml>false</failOnMissingWebXml>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

If you are using Eclipse, be sure to refresh your project (select your project→ right click→ Maven→ Update Project)

Create Person class as a model class at src/main/java/com/app/model/Person.java such as the following:

package com.app.model;

public class Person {

	private String name;

	private int age;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

}

Create ExampleService as sREST service at src/main/java/com/app/service/ExampleService.java, such as the following:

package com.app.service;

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import com.app.model.Person;

@Path("/example")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public class ExampleService {

	@GET
	@Path("hello")
	public String sayHello() {
		return "Hello from uncle Jalal";
	}

	@GET
	@Path("/hello/{name}")
	public String sayHelloWithPathParam(@PathParam(value = "name") String name) {
		return "Hello, " + name;
	}

	@POST
	@Path("/hello")
	public String sayHelloWithBody(Person p) {
		return "Hello, " + p.getName() + ", your age is: " + p.getAge();
	}
}

Create App class at src/main/java/com/app/App.java for quick testing with the following contents:

package com.app;

import javax.ws.rs.ApplicationPath;

import com.jk.web.embedded.JKWebApplication;
import com.jk.web.services.server.JKServiceConfig;

@ApplicationPath("app")
public class App extends JKServiceConfig{

	/**
	 *
	 * @param args
	 */
	public static void main(String[] args) {
		JKWebApplication.run(8080,false);
	}

}

Run your App class, you should see something like this in your console:

Figure 1. Navigate to http://localhost:8080/app/example/hello , you should see something like this:

The available end-points are:

GET: http://localhost:8080/app/example/hello
GET: http://localhost:8080/app/example/hello/{name}
POST: http://localhost:8080/app/example/hello with Person JSON object with name and age fields in the body

Now, you can test the Microservice with your preferred API client such as Talend or PostMan.

To call the this Microservice from Java client, you can follow this - Create Simple Microservice Client

Full example source-code can be found at https://github.com/smartapi-com/smart-cloud-microservice