@Controller Annotation in Spring

@Controller annotation is a type of annotation provided by Spring Framework. It is used to mark a class as a Spring MVC controller. It is generally used with @RequestMapping annotation to map HTTP requests to specific methods in a controller class.

How to User @Controller Annotation

To use @Controller annotation in Spring Boot, follow the below steps:

Step 1: Annotate Java class with @Controller Annotation

The first step is to create a Java class and annotate it with @Controller annotation.

@Controller
public class MyWelcomeController {

}

Step 2: Add Request Mapping Methods

The next step is to define methods in the controller class and annotate them with @RequestMapping annotation. @RequestMapping annotation maps HTTP requests to specific methods in the controller class.

For example, in the below code example, the @GetMapping annotation will map HTTP GET request to a Java method it uses.

@RequestMapping("/welcome")
public String welcome() {
  return "welcome";
}

The above Java method will be triggered if the user sends HTTP GET request to a /welcome URL path.

Step 3: Create a View File

In the above code example, the welcome() method returns a string value “welcome”. This means that we need to create a view file called welcome.jsp. If your project is not configured to support JSP, you can read the following tutorial: Configure JSP Support in Spring MVC Application.

<html>
<head><title>Welcome Page</title></head>
<body>

 <h1>Welcome</h2>

</body>
</html>

Step 5: Run Your Application

Now, you can run the Spring Boot application and access the URL corresponding to the @RequestMapping value (e.g. http://localhost:8080/welcome). This will trigger the corresponding method in the controller class and render the view file. In our case, it will trigger the welcome() method defined in the MyWelcomeController class.

Conclusion

@Controller annotation is a useful tool in Spring Boot for creating MVC controllers and handling HTTP requests. It allows developers to easily map specific methods in a controller class to specific HTTP requests, making it easy to develop web applications with Spring Boot.

To learn more, check out the Spring Web MVC tutorials page.