The main difference between ‘@Controller‘ and ‘@RestController‘ annotations in Spring MVC is in the way they handle the HTTP response body.
‘@Controller‘ annotation is used to create a Spring MVC controller class that is responsible for handling incoming HTTP requests. It usually handles the request and prepares the response by returning a view name, which is then resolved by a view resolver. In this way, the ‘@Controller‘ annotation is used to manage the flow of views in a Spring MVC application.
On the other hand, ‘@RestController‘ annotation is used to create a class that provides a RESTful web service. It behaves like a combination of the ‘@Controller‘ and ‘@ResponseBody‘ annotations, i.e., it handles the incoming request and returns the data directly to the client, without the need of a view resolver.
‘@RestController‘ annotations ensure that the response body is serialized directly to the HTTP response in a format such as JSON or XML, without a view. This approach is particularly useful for building APIs that communicate in a standard format like JSON or XML.
For example, consider the following code snippet:
@Controller
public class MyController {
@GetMapping("/greeting")
public String greeting() {
return "Hello, world!";
}
}In this code snippet, the ‘@Controller‘ annotation is used to create a controller class that handles incoming GET requests to the ‘/greeting‘ URL path. The method ‘greeting()‘ prepares a view named ‘Hello, world!‘ which is resolved by a view resolver to render the final response.
On the other hand, consider the following code snippet:
@RestController
public class MyRestController {
@GetMapping("/greeting")
public String greeting() {
return "Hello, world!";
}
}In this code snippet, the ‘@RestController‘ annotation is used to create a RESTful web service that handles incoming GET requests to the ‘/greeting‘ URL path. The method ‘greeting()‘ returns a String "Hello, world!", which is directly serialized and sent as the response body in the format requested by the client.
In summary, the use of ‘@Controller‘ or ‘@RestController‘ depends on the nature of your web application - if you are building an API, it is better to use the ‘@RestController‘ annotation, while if you are building a web application that uses views, it is better to use the ‘@Controller‘ annotation.