Quick Summary:

The blog covers the 10 best Spring Boot annotations for building effective and efficient applications. Each annotation addresses particular solutions to the issues and controls the configuration. Using annotations can streamline your development process, improve performance, and stay ahead of the curve in Spring Boot development.

Table of Contents

Introduction

Java web development constantly evolves and remains on top of the latest trends and technologies. One framework that signifies standing ahead of time with increasing popularity is Spring Boot.

A survey shows over 80% of developers use Spring Boot for web development projects. The framework streamlines the application development approach, making it more efficient and productive.

The significant benefit of Spring Boot is it allows developers to focus solely on writing their code, while in the background, it takes care of the rest.

Now that you have understood its significance, let’s look at the essential part of Spring Boot, i.e., annotations. This blog will unfold the top 10 Spring Boot annotations list with explanations and the best practices for using Spring Boot annotations.

10 Spring Boot Annotations to Use For Your Next Project

Here are the different annotations in Spring Boot to use to simplify the development process:

10 Spring Boot Annotations

1. @SpringBootApplication

The @SpringBootApplication annotation is a prominent class of multiple annotations that combines three other Spring Boot annotations, such as @ComponentScan, @Configuration, and @EnableAutoConfiguration. It is placed in the root package and a meta-annotation of the application.

Using the @SpringBootApplication annotation, developers can configure the application and take benefit of the various features provided by the Spring Boot framework. Also, by integrating multiple annotations’ functionality, you can reduce the boilerplate code required to configure applications.

@SpringBootApplication allows you to simplify the configuration of the Spring application. This annotation helps to customize and modify the properties of applications. As a result, developers can tailor web applications that match project requirements.

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@SpringBootApplication
public class MyApplication {

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

}

2. @Configuration

The @Configuration is a class-based annotation that defines one or more bean methods in the class. The purpose of a configuration class is to indicate the application context, like service and other application components.

As a result, developers can create highly flexible and efficient applications that can adapt to requirement changes quickly. @Configuration annotation supports importing other classes. The Spring Boot custom annotation can separate configuration classes based on domain or functionality.

Also, a configuration class can activate or deactivate particular components based on the environment. With the @Configuration, Java developers can write codes by replacing large XML configuration files.

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@Configuration
public class MyConfiguration {
    
    @Bean
    public MyService myService() {
        return new MyServiceImpl();
    }
    
    @Bean
    public MyController myController(MyService myService) {
        return new MyControllerImpl(myService);
    }
}

3. @PathVariable

The @PathVariable is used to measure dynamic parameters from the request URI and map them to method parameters in a controller. The annotation helps develop RESTful web services, allowing you to manage variable parameters.

Also, it enables developers to handle incoming requests and dynamic parameters without any complex writing code. Hence, with @PathVariable, you can define more accurate mapping while requesting URIs and controller methods.

By using SpringBoot annotation, you can get easily customizable and integrate it with other annotations in Spring Boot such as @RequestMapping and @GetMapping. The powerful annotation ensures that applications remain secure.

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@RestController
@RequestMapping("/users")
public class UserController {
    
    @GetMapping("/{userId}")
    public ResponseEntity<User> getUserById(@PathVariable Long userId) {
        // logic to retrieve user by ID from database
        User user = userService.getUserById(userId);
        
        // check if user exists
        if (user == null) {
            return ResponseEntity.notFound().build();
        }
        
        return ResponseEntity.ok(user);
    }
    
}

4. @RequestBody

In web applications, @RequestBody indicates a method parameter that binds the HTTP request body in the controller method. The request’s body is mapped when users send requests to the server.

The request includes data from the requested body and helps to resolve the method. However, it depends on the content type, as the deserialization is automatic. The data can be in various forms, such as plain text, XML, and JSON.

@Requestbody is used to send and transform the Java object returned from the controller to the resource representation requested by RESTful. For instance, if the user sends a request body with details about the new users, the annotations will bind the API to the user object.

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@RestController
@RequestMapping("/api")
public class MyController {

    @PostMapping("/data")
    public ResponseEntity<String> processData(@RequestBody MyData data) {
        // Process the data received in the request body
        // ...
        return ResponseEntity.ok("Data processed successfully");
    }

    // Other controller methods
    // ...
}

5. @Autowired

In SpringBoot annotation, @Autowired is used to inject the dependency of one bean into another. The spring-managed object is implemented into another object that a class needs to perform.

Thus, when you annotate a field, a method with @Autowired, Spring Boot will inject the dependency automatically and find the bean that matches that field or parameter. The @Autowired is used to inject in three ways: field, setter, and constructor injection.

In other words, Autowired annotation in Spring Boot manages the entire life cycle of the object.

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@Service
public class MyService {
    
    @Autowired
    private MyRepository myRepository; // field injection
    
    @Autowired
    public MyService(@Qualifier("myRepositoryImpl") MyRepository myRepository) {
        this.myRepository = myRepository; // constructor injection
    }
    
    @Autowired
    public void setMyRepository(@Qualifier("myRepositoryImpl") MyRepository myRepository) {
        this.myRepository = myRepository; // setter injection
    }
}

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6. @RestController

The @RestController combines the functionality of @Respondbody and @Controller annotations. The annotation makes creating RESTful endpoints that return XML, JSON, and other types of responses easier.

RestController annotations in Spring Boot are also used to respond to plain text, images, or PDF documents. In addition, Spring Boot sets the HTTP response as a default, but with Rest Controller annotation, it can customize the method.

Also, by annotating the controller class with Rest Controller annotation, you do not need to add @Respondbody for request mapping methods.

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@RestController
public class MyRestController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello, world!";
    }   
}

7. @Bean

The @Bean is a method-level annotation widely used in Spring Boot applications. Bean annotation is a direct analog of the XML element, which indicates that the Spring container should register a method.

Spring bean annotations are the objects that can be injected into other components or other beans. Also, it can be an alternative to the XML tag. @Bean annotations are singletons, meaning they can be created or shared with the entire application context.

In a nutshell, @Bean annotations help to create and manage beans in Spring Boot applications using various methods.

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@Configuration
public class MyConfiguration {
    
    @Bean
    public MyBean myBean() {
        return new MyBean();
    }    
}

8. @EnableAutoConfiguration

The annotation allows the automatic configuration of your Spring Boot applications. Enable Auto Configuration annotations to define the Spring components and configure them automatically.

The autoconfigured beans are present in the classpath and make developer work simpler by providing the required beans from the classpath and configuring it to run the applications. In Spring Boot, @EnableAutoConfiguration annotation considers the default package of the class.

Also, if you don’t want to attribute some classes to auto configuration, the Spring framework boot allows you to exclude them from auto-configurations manually.

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@Configuration
@EnableAutoConfiguration
public class EmployeeApplication {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(EmployeeApplication.class, args);
        // ...
    }
}

9. @Components

The @Components is used to mark the Java class in the Spring applications. The Spring IoC container manages the component annotations and is responsible for the lifecycle of the components, such as initializing, creating, or destroying them.

As a result, components can represent any object in the application, including services and controllers. Also, when the Java class marked the @Component annotation, Spring Boot detected the components with the help of the classpath.

Moreover, components are used in conjunction with @Autowired and @Qualifier to inject the dependencies of the elements.

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@Component
public class MyComponent {
    // component logic here
}

@Controller
public class MyController {
    // controller logic here
}

10. @Repository

The @Repository annotation is used to interact with different databases, such as NoSQL databases and relational databases. Also, when a Java class is marked with @Repository annotation, Spring Boot automatically creates and adds the required context.

The class annotated with Repository is an element of the data access layer and provides an API for interacting, which allows the developer to write less code. The @Repository annotation is a marker for the class that performs the role of data access object.

Using @Repository, you can develop flexible, reusable, and modular repositories that the Spring Data framework can easily handle.

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@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    User findByUsername(String username);
}

5 Best Practices for Using Spring Boot Annotations

Following the 5 best practices for using SpringBoot annotations will help to streamline the project process:

1. Use @RequestMapping Instead of @GetMapping

@GetMapping and @PostMapping are specific HTTP method annotations that require more requests. However, using @RequestMapping will be more helpful as you manage multiple HTTP methods for the same URL.

2. Avoid Unnecessary Annotations Sparingly

As there are numerous annotations, it is essential to use SpringBoot annotations that are required and necessary. Because overusing annotations will make your code harder to read and more challenging to maintain.

3. Implement @ConditionalOnProperty For Simple Conditions

For efficient applications using Spring, utilizing the @ConditionalOnProperty will enable or disable configurations based on the property’s value. It will make your work manageable and configure your applications based on external factors.

4. Integrate Tests With ComponentScan

Using @ComponentScan in integration tests leverages powerful annotations. Also, it ensures that your test is running accurately based on the behavior of your application and reflects the potential issues that may appear during the run.

5. Use @ControllerAdvice For Global Exception Handling

The @ControllerAdvice allows you to define global expectation handles that will be implemented to all controllers in the Spring applications. It helps to resolve this by providing precise and consistent messages to the Spring Boot applications.

Conclusion

The powerful Spring Boot annotations in your development process can enhance your web applications’ performance, maintainability, and scalability. Furthermore, it simplifies and robust the development with various components.

This blog highlights the top 10 Spring Boot annotations to boost productivity and streamline your project. Each annotation provides advantages and features that can take your applications to the next level.

So, if you are not using annotations for Spring Boot applications, now is a great time to start. By incorporating them into your development flow, you can stay one step ahead in 2024 and beyond.

Frequently Asked Questions (FAQs)

No, using @RestController instead of @Controller while annotating in the Spring Boot framework is not mandatory. Both have similar purposes, but @RestController is used for developing Restful web services.

Yes! you can use the @Value annotations to inject values from the external properties into Spring Beans for your applications. It helps to externalize your configuration and make it more flexible.

You should use the @ConditionalOnProperty annotations to conditionally configure the application based on the values of properties in the configuration files. With this annotation, you can specify a name and value that must be present in the configuration to run applications.

You can use @SpringBootApplication as it combines three annotations: @Configuration, @ComponentScan, and @EnableAutoConfiguration. However, you can add additional annotations if you require more specific functionality.

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