Interservice Communication

In this tutorial, we will see how to call one service from another. For that, let’s first create a service with one simple get mapping and one post mapping.

Step 1 : Create one microservice using spring starter project in sts.

pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.4</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.javatrainingschool</groupId>
	<artifactId>calculationService</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>calculationService</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</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>

Let’s define one getMapping and one PostMapping in the controller class

CalculationController.java

package com.javatraining;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/calc")
public class CalculationController {

	@GetMapping("/info")
	public String info() {
		return "This is a simple get mapping from Calculation controller";
	}
	
	@PostMapping("/multiply")
	public String multiply(@RequestBody Numbers num) {
		int result = num.getNum1() * num.getNum2();
		return "the result = " + result;
	}	
}

Numbers.java

package com.javatraining;

public class Numbers {

	private int num1;
	private int num2;

	public int getNum1() {
		return num1;
	}

	public void setNum1(int num1) {
		this.num1 = num1;
	}

	public int getNum2() {
		return num2;
	}

	public void setNum2(int num2) {
		this.num2 = num2;
	}

}

Define a port on which the server is to run

application.properties file

server.port=8081

Run and test the service

http://localhost:8081/calc/info

Step 2 : Create second Service

Create another service. From this service, we will call the above service

pom.xml for this service is like below

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.4</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.javatrainingschool</groupId>
	<artifactId>getService</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>getService</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</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>

Add Below to the main class

@Bean
public RestTemplate restTemplate() {
    return new RestTemplate();
}

package com.javatraining;

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

@SpringBootApplication
public class GetServiceApplication {

	public static void main(String[] args) {
		SpringApplication.run(BootWithMongoApplication.class, args);
	}
	
	@Bean
	public RestTemplate restTemplate() {
    	      	return new RestTemplate();
	}
}

Controller for this service

package com.javatraining;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@RequestMapping("/get")
public class GetController {
	
	@Autowired
	RestTemplate restTemplate;
	
	@GetMapping("/calcInfo")
	public String getCalcInfo() {
		String url="http://localhost:8081/calc/info";
		return restTemplate.getForObject(url, String.class);
	}
	
	@PostMapping("/multiply")
	public ResponseEntity<String> multiply(@RequestBody Numbers num){
		
		String url="http://localhost:8081/calc/multiply";
		ResponseEntity<String> result = restTemplate.postForEntity
				(url, num, String.class);
		
		return result;
	}
}

Numbers.java

package com.javatraining;

public class Numbers {

	private int num1;
	private int num2;

	public int getNum1() {
		return num1;
	}

	public void setNum1(int num1) {
		this.num1 = num1;
	}

	public int getNum2() {
		return num2;
	}

	public void setNum2(int num2) {
		this.num2 = num2;
	}

}

add below property

server.port=8082

Run the service and test

Post Request