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Tutorials > Microservices > Building Microservices

Building Microservices

Here's an example of building a RESTful Microservice using Spring Boot, which exposes a simple API to retrieve a list of products.

  • First, create a new Spring Boot project using your preferred IDE or build tool. Here, I'll use Maven to create a new project with the Spring Boot Web and Spring Data JPA starters:
xml
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<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 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>product-service</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <java.version>11</java.version>
        <spring-boot.version>2.6.2</spring-boot.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>${spring-boot.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>${spring-boot.version}</version>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.200</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>
  • Create a Product entity class that will be persisted using Spring Data JPA:
java
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@Entity
public class Product {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotBlank
    private String name;

    private String description;

    @DecimalMin(value = "0")
    private BigDecimal price;

    // getters and setters
}
  • Create a Product repository interface that extends the Spring Data JPA CrudRepository:
java
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@Repository
public interface ProductRepository extends CrudRepository<Product, Long> {

}
  • Create a Product service class that encapsulates the business logic for retrieving products:
java
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@Service
public class ProductService {

    @Autowired
    private ProductRepository productRepository;

    public List<Product> getProducts() {
        return (List<Product>) productRepository.findAll();
    }

    public Product getProductById(Long id) {
        return productRepository.findById(id).orElse(null);
    }

}
  • Create a REST controller class that exposes the ProductService API via HTTP:
java
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@RestController
@RequestMapping("/products")
public class ProductController {

    @Autowired
    private ProductService productService;

    @GetMapping
    public List<Product> getProducts() {
        return productService.getProducts();
    }

    @GetMapping("/{id}")
    public Product getProductById(@PathVariable Long id) {
        return productService.getProductById(id);
    }

}
  • Run the application using your IDE or build tool. The Spring Boot Web starter includes an embedded Tomcat server, so you can run the application using the main method in the ProductServiceApplication class:
java
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@SpringBootApplication
public class ProductServiceApplication {

    public static void main(String[] args) {
        SpringApplication.run(ProductServiceApplication.class, args);
    }

}
  • Here's how you can test the API:

  • Use a tool like Postman or cURL to test the API endpoints. For example, to retrieve all products, you can make an HTTP GET request to http://localhost:8080/products. To retrieve a specific product by ID, you can make an HTTP GET request to http://localhost:8080/products/{id}, where {id} is the ID of the product you want to retrieve.

  • Another way to test the API is to use a web browser. If you visit http://localhost:8080/products in your web browser, you should see a JSON array containing all the products in the database.

That's it! With just a few lines of code, we've built a simple Spring Boot Microservice that exposes a RESTful API for retrieving product information. Of course, this is just a basic example, and a real-world Microservice would likely include additional functionality such as authentication, caching, load balancing, and other features to make it more scalable, resilient, and fault-tolerant. But hopefully, this example gives you a good starting point for building your own Microservices with Spring Boot.




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