How to Create a Microservice with Spring Boot: Simple Guide

To create a microservice with Spring Boot, start a new project with spring-boot-starter-web dependency, define a @RestController to handle HTTP requests, and run the application as a standalone service. This creates a lightweight, independent service that can communicate over HTTP.

Syntax

Here is the basic syntax to create a Spring Boot microservice:

• @SpringBootApplication: Marks the main class to enable Spring Boot features.
• @RestController: Defines a class that handles HTTP requests.
• @GetMapping: Maps HTTP GET requests to a method.
• SpringApplication.run(): Starts the Spring Boot application.

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

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

@RestController
class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello from Spring Boot Microservice!";
    }
}

Example

This example shows a complete Spring Boot microservice that responds with a greeting message when accessed at /hello.

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

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

@RestController
class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello from Spring Boot Microservice!";
    }
}

Output

When you run this application and visit http://localhost:8080/hello in a browser, you will see:

Hello from Spring Boot Microservice!

Common Pitfalls

Common mistakes when creating Spring Boot microservices include:

• Not adding spring-boot-starter-web dependency, so the web server won't start.
• Forgetting @RestController annotation, so endpoints are not exposed.
• Using @Controller without @ResponseBody, which returns views instead of JSON or text.
• Not running the application with SpringApplication.run().

java

/* Wrong: Missing @RestController, so endpoint won't work */
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;

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

class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello!";
    }
}

/* Right: Add @RestController to expose endpoint */
import org.springframework.web.bind.annotation.RestController;

@RestController
class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello!";
    }
}

Quick Reference

Summary tips for creating Spring Boot microservices:

• Use @SpringBootApplication on main class.
• Add spring-boot-starter-web dependency for web support.
• Define REST endpoints with @RestController and @GetMapping.
• Run the app with SpringApplication.run().
• Test endpoints via browser or tools like curl/Postman.

Key Takeaways

Start a Spring Boot project with spring-boot-starter-web to create a microservice.

Use @RestController and mapping annotations to define HTTP endpoints.

Run your microservice with SpringApplication.run() to start the embedded server.

Test your microservice by accessing its endpoints via HTTP.

Avoid missing annotations or dependencies to prevent common errors.