Service-to-service communication in Spring Boot - Mini Project: Build & Apply

Service-to-service communication with Spring Boot

📖 Scenario: You are building two small Spring Boot services that need to talk to each other. The first service will call the second service to get a greeting message.This is like when you ask a friend to get information for you from another friend. Here, one service asks another service for data.

🎯 Goal: Create two Spring Boot services where ServiceA calls ServiceB using RestTemplate to get a greeting message and display it.

📋 What You'll Learn

Create a Spring Boot application for ServiceB that returns a greeting string at /greeting endpoint

Create a Spring Boot application for ServiceA that calls ServiceB's /greeting endpoint using RestTemplate

Configure the base URL of ServiceB in ServiceA as a variable

Display the greeting message received from ServiceB in ServiceA's /show-greeting endpoint

💡 Why This Matters

🌍 Real World

Microservices often need to communicate with each other to share data or trigger actions. This project shows the basic way to do that using REST calls in Spring Boot.

💼 Career

Understanding service-to-service communication is essential for backend developers working with microservices architecture, enabling them to build scalable and modular applications.

1

Create ServiceB with a greeting endpoint

Create a Spring Boot controller class called GreetingController in ServiceB with a method getGreeting() mapped to /greeting that returns the string "Hello from ServiceB!".

Spring Boot

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetingController {
    // Your code here
}

Need a hint?

Use @RestController and @GetMapping annotations to create the endpoint.

2

Configure ServiceB base URL in ServiceA

In ServiceA, create a String variable called serviceBBaseUrl and set it to "http://localhost:8081" which is the base URL of ServiceB.

Spring Boot

// Your code here

Need a hint?

This variable will hold the address where ServiceB is running.

3

Use RestTemplate in ServiceA to call ServiceB's greeting

In ServiceA, create a RestTemplate object called restTemplate. Then write a method fetchGreeting() that uses restTemplate.getForObject to call serviceBBaseUrl + "/greeting" and returns the greeting string.

Spring Boot

String serviceBBaseUrl = "http://localhost:8081";
// Your code here

Need a hint?

Use new RestTemplate() to create the client and getForObject to call the URL.

4

Create endpoint in ServiceA to show greeting from ServiceB

In ServiceA, create a Spring Boot controller class called ShowGreetingController with a method showGreeting() mapped to /show-greeting. This method should call fetchGreeting() and return the greeting string.

Spring Boot

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

// Your code here

Need a hint?

Use @RestController and @GetMapping to create the endpoint that calls fetchGreeting().