Spring Boot Microservices RestTemplate Example with E-commerce

In this tutorial, we'll create two Spring Boot microservices for an e-commerce application: product-service and order-service. The order-service will communicate with the product-service to fetch product details using RestTemplate. We'll use the latest Spring Boot version 3.2+.

Prerequisites

• JDK 17 or later
• Maven or Gradle
• IDE (IntelliJ IDEA, Eclipse, etc.)

Step 1: Create the Projects

We'll create two Spring Boot projects: product-service and order-service.

Step 2: Set Up product-service

2.1 Create the Project

Use Spring Initializr to create a new project with the following dependencies:

• Spring Web
• Spring Boot Actuator

2.2 Configure application.properties

Set up the application properties to run on port 8081.

server.port=8081

2.3 Create a Product Model

Create a simple Product model to represent the product data.

package com.example.productservice;

public class Product {
    private String id;
    private String name;
    private double price;

    // Constructor, getters, and setters
    public Product(String id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

2.4 Create a Controller

Create a controller to handle product-related requests.

package com.example.productservice;

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

@RestController
public class ProductController {

    @GetMapping("/products/{id}")
    public Product getProduct(@PathVariable String id) {
        // In a real application, this data would come from a database
        return new Product(id, "Sample Product", 99.99);
    }
}

Step 3: Set Up order-service

3.1 Create the Project

Use Spring Initializr to create a new project with the following dependencies:

• Spring Web
• Spring Boot Actuator
• Spring Boot Starter Web

3.2 Configure application.properties

Set up the application properties to run on port 8082 and configure the URL for the product-service.

server.port=8082
product.service.url=http://localhost:8081/products

3.3 Create a RestTemplate Bean

Create a configuration class to define a RestTemplate bean.

package com.example.orderservice;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class AppConfig {

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

3.4 Create a Product Client

Create a service class to communicate with the product-service.

package com.example.orderservice;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class ProductServiceClient {

    private final RestTemplate restTemplate;
    private final String productServiceUrl;

    public ProductServiceClient(RestTemplate restTemplate, @Value("${product.service.url}") String productServiceUrl) {
        this.restTemplate = restTemplate;
        this.productServiceUrl = productServiceUrl;
    }

    public Product getProductById(String productId) {
        return restTemplate.getForObject(productServiceUrl + "/" + productId, Product.class);
    }
}

3.5 Create a Product Model

Create a Product model to match the one in product-service.

package com.example.orderservice;

public class Product {
    private String id;
    private String name;
    private double price;

    // Constructor, getters, and setters
    public Product() {}

    public Product(String id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

3.6 Create a Controller

Create a controller to handle order-related requests and use the ProductServiceClient to fetch product details.

package com.example.orderservice;

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

@RestController
public class OrderController {

    private final ProductServiceClient productServiceClient;

    public OrderController(ProductServiceClient productServiceClient) {
        this.productServiceClient = productServiceClient;
    }

    @GetMapping("/orders/{productId}")
    public String createOrder(@PathVariable String productId) {
        Product product = productServiceClient.getProductById(productId);
        return "Order created for product: " + product.getName() + " with price: $" + product.getPrice();
    }
}

Step 4: Run the Microservices

1. Start product-service by running ProductServiceApplication.
2. Start order-service by running OrderServiceApplication.

Step 5: Test the Communication

Open your browser or use a tool like Postman to test the endpoints:

• product-service: http://localhost:8081/products/1
• order-service: http://localhost:8082/orders/1

The response from order-service should include the product details fetched from product-service.

Conclusion

You have successfully set up two Spring Boot microservices and demonstrated communication between them using RestTemplate. This example can be expanded to include more complex inter-service communication patterns and additional microservices.