Micronaut vs Spring Boot: A Detailed Comparison

Micronaut and Spring Boot are popular frameworks for developing microservices in Java. They offer robust features for REST API, but their approach towards dependency injection, start-up time, and memory usage differ. This article presents a detailed comparison between both frameworks on various parameters such as implementation, performance metrics, and usefulness of each framework.

The Micronaut Framework Overview

This is a recently developed framework aimed to develop faster microservices and serverless services. Its main feature of compile-time dependency injection results in faster startup times and less memory usage. It has built-in support for cloud environments and serverless deployments and can be integrated with GraalVM. This makes the Micronaut framework suitable for applications where resource utilization is paramount.

The Spring Boot Framework Overview

Spring Boot has been in practice for more than a decade; therefore, it is a mature framework known for its ease of use, powerful features, and extensive ecosystem. It uses runtime dependency injection and provides seamless integration with any other module from the Spring ecosystems, such as Spring Data, Spring Security, Spring Cloud, etc. It provides autoconfiguration and embedded servers and is backed by a large, active community with huge documentation. Therefore, the mentioned key features make it versatile for a wide variety of applications.

The Rest API Under Consideration: Task Management Service

A simple REST API is created using both frameworks and will be compared for resource utilization, ease of use, performance, etc. The REST API will have the following endpoints.

• GET /tasks – Retrieve all tasks
• GET /tasks/{id} – Retrieve a specific task by its Id
• POST /tasks – Add a new task

Micronaut Implementation

The project structure can be referred to from Micronaut's official documentation. To create the above, REST API, Maven, and Java 23 are used as below. The pom.xml must have the below Micronaut dependency.

        <dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-http-server-netty</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut.serde</groupId>
			<artifactId>micronaut-serde-jackson</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-http-client</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-inject</artifactId>
		</dependency>

The ControllerClass in the Micronaut Framework.

@Controller("/tasks")
public class TaskController {
    @Inject
    TaskService taskService;
    @Get("/hello")
    public String helloWorld(){
        return "Hello World";
    }
    @Post(value = "/",consumes = "application/json", produces = "application/json")
    public Task addTask(@Body Task task) {
        return taskService.saveTask(task);
    }

    @Get(produces = "application/json")
    public List<Task> findAllTasks() {
        return taskService.getTasks();
    }

    @Get("/{id}")
    public Task findTaskById(@PathVariable int id) {
        return taskService.getTaskById(id);
    }

    @Put
    public Task updateTask(@Body Task task) {
        return taskService.update(task);
    }

}

REST API: get all tasks – Postman output:

What Annotations Can We Use for Rest API Using Micronaut?

1. @Controller – Used to make a class controller, indicating it can handle HTTP requests
2. @Get, @Post, @Put, and @Delete – Used on methods inside the controller class to specify respective HTTP methods
3. @PathVariable – Used to describe method parameters to access values from the URL
4. @Inject – Equivalent to @Autowired annotation used in Spring Boot
5. @Singleton – Used for a bean, which means that the bean will be created once and available throughout the lifecycle of the application
6. @Body – A method/function parameter that denotes that the request body must be deserialized
7. @RequestMapping – Helpful while defining base paths when there are multiple controller methods/functions
8. @Qualifier – Important to use in case there are multiple beans of the same type, and the same annotation is present in the Spring Boot
9. @Serdeable – Used for the input request class, which will be serialized when reading the request body

Spring Boot Implementation

The basic project skeleton can be generated from Spring Initializr. The pom.xml for REST API must have a spring-boot-starter-web dependency as below.

<parent>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-parent</artifactId>
	<version>3.4.1</version>
	<relativePath/> <!-- lookup parent from repository -->
</parent>
<dependencies>
	 <dependency>
		<groupId>org.springframework.boot</groupId>
	    <artifactId>spring-boot-starter-web</artifactId>
     </dependency>
</dependencies>

The RestController class in the Spring Boot framework is as below:

@RestController
@RequestMapping("/api/tasks")
public class TaskController {

    @Autowired
    TaskService taskService;
    @GetMapping("/hello")
    public String helloWorld(){
        return "Hello World";
    }

    @PostMapping(consumes = "application/json", produces = "application/json")
    public Task addTask(@RequestBody Task task) {
        return taskService.saveTask(task);
    }

    @GetMapping(produces = "application/json")
    public List<Task> findAllTasks() {
        return taskService.getTasks();
    }

    @GetMapping("/{id}")
    public Task findTaskById(@PathVariable int id) {
        return taskService.getTaskById(id);
    }

    @PutMapping
    public Task updateTask(@RequestBody Task task) {
        return taskService.update(task);
    }
}

REST API: get all tasks – Postman output:

Comparative Overview: Spring Boot vs. Micronaut