Microservices have become the architecture of choice for modern web applications. This is because microservices offer agility, scalability, and availability – key requirements for modern web applications.
Spring Boot is a popular framework for building Java-based web applications, and it’s also great for building microservices. In this tutorial, we’ll discuss how to build microservices with Spring Boot.
What are Microservices?
Microservices are small, independent services that work together to form a larger application. Each microservice is responsible for a specific function, such as user authentication, order processing, or product search. Microservices communicate with each other using lightweight protocols like HTTP.
One of the key benefits of microservices is that they offer agility. Since each microservice is independent, it can be developed, tested, and deployed individually. This allows developers to release new features more quickly and with less risk.
Another benefit of microservices is that they offer scalability. Since each microservice can be deployed independently, it’s easier to scale individual services as needed. For example, if a product search service is getting bogged down with traffic, it can be scaled up without affecting other services.
Finally, microservices offer availability. Since each microservice is independent, the failure of one doesn’t necessarily affect the others. This makes the overall application more resilient and reliable.
Building Microservices with Spring Boot
Spring Boot is a popular framework for building Java-based web applications. It provides a number of features that make building microservices easier, such as RESTful web services, embedded servers, and auto-configuration.
In this tutorial, we’ll build a simple microservice with Spring Boot. Our microservice will allow users to retrieve information about products in an online store.
Creating a Spring Boot Project
To get started, we’ll need to create a new Spring Boot project. There are a couple of ways to do this, but one of the easiest is to use the Spring Initializr.
- Open a web browser and navigate to https://start.spring.io/
- Fill out the form to configure your project. For our project, we’ll use the following settings:
- Project type: Maven Project
- Packaging: Jar
- Java version: 11
- Language: Java
- Spring Boot version: 2.5.1
- Group: com.example
- Artifact: product-service
- Name: product-service
- Description: Microservice for retrieving products
- Package Name: com.example.productservice
- Dependencies: Spring Web, Spring Data JPA, H2 Database
- Click the “Generate” button to download your project.
Creating the Product Model
Next, we’ll create a model for our products. We’ll use the following fields:
- id: The unique identifier for the product
- name: The name of the product
- description: A brief description of the product
- price: The price of the product
- imageUrl: The URL for an image of the product
To create the model, create a new file called Product.java in the src/main/java/com/example/productservice directory.
package com.example.productservice;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Product {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private String description;
private double price;
private String imageUrl;
// getters and setters
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getImageUrl() {
return imageUrl;
}
public void setImageUrl(String imageUrl) {
this.imageUrl = imageUrl;
}
}
The @Entity annotation tells Spring that this class represents a table in the database. The @Id annotation tells Spring that the id field should be the primary key for the table.
Creating the Product Repository
Next, we’ll create a repository for our products. The repository is responsible for interacting with the database to perform CRUD (create, read, update, delete) operations on our products.
To create the repository, create a new file called ProductRepository.java in the src/main/java/com/example/productservice directory.
package com.example.productservice;
import org.springframework.data.repository.CrudRepository;
public interface ProductRepository extends CrudRepository<Product, Long> { }
The CrudRepository interface provides a number of methods for performing CRUD operations on our products. By extending this interface and passing our Product class and the type of the primary key (Long), we get all of these methods for free.
Creating the Product Controller
Next, we’ll create a controller for our products. The controller is responsible for handling HTTP requests and returning responses.
To create the controller, create a new file called ProductController.java in the src/main/java/com/example/productservice directory.
package com.example.productservice;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/products")
public class ProductController {
@Autowired
private ProductRepository repository;
@GetMapping("/{id}")
public Product getProduct(@PathVariable("id") Long id) {
return repository.findById(id).orElse(null);
}
}
The @RestController annotation tells Spring that this class is a controller for RESTful web services. The @RequestMapping annotation specifies that this controller will handle requests with the /products prefix. The @Autowired annotation tells Spring to automatically inject an instance of the ProductRepository when this controller is created.
The @GetMapping annotation specifies that this method will handle HTTP GET requests with a URL that includes an id parameter. The @PathVariable annotation tells Spring to inject the value of the id parameter from the URL into the id parameter of the method.
Inside the method, we call the findById method of the ProductRepository to retrieve the Product with the specified id. If no Product with that id exists, we return null.
Running the Application
We’ve now created all the necessary components for our microservice. To run the application, open a terminal window and navigate to the root directory of the project. Type the following command:
mvnw spring-boot:run
This will start the embedded server and deploy our application. The terminal window should display some output indicating that the application has started successfully.
Accessing the Product Service
Our microservice is now up and running and we can start accessing it. To retrieve information about a product, we can make a HTTP GET request to the appropriate URL.
If you’re running the application locally, the base URL for the product service is http://localhost:8080/products`. To retrieve information about a specific product, we can append the product’sidto the end of the URL. For example, to retrieve information about the product with anidof 1, we can make a GET request to the URLhttp://localhost:8080/products/1`.
Conclusion
In this tutorial, we’ve discussed how to build microservices with Spring Boot. We’ve created a simple microservice that allows users to retrieve information about products in an online store.
Creating microservices with Spring Boot is relatively easy, thanks to the many features that Spring Boot provides. We hope this tutorial has been helpful in getting you started with building microservices with Spring Boot.