Difference between @Controller vs @RestController in Spring

When developing web applications using the Spring framework, you may come across two annotations: @Controller and @RestController. While both are used for handling HTTP requests, there are some key differences between them. In this article, we will explore these differences and understand when to use each annotation.

@Controller Annotation

The @Controller annotation is used to mark a class as a controller in the Spring MVC framework. It is typically used to handle traditional web applications where the response is rendered using a view technology, such as JSP or Thymeleaf.

A controller class annotated with @Controller can have methods annotated with @RequestMapping or other request mapping annotations to handle specific HTTP requests. These methods return a logical view name or a ModelAndView object, which is resolved by the view resolver to render the response.

Here's an example of a controller class using @Controller:

@Controller
public class MyController {
    
    @RequestMapping("/hello")
    public String hello() {
        return "hello"; // returns the logical view name
    }
}

@RestController Annotation

The @RestController annotation, introduced in Spring 4, combines the @Controller and @ResponseBody annotations. It is used to create RESTful web services that return JSON or XML responses directly, without the need for a view resolver.

A class annotated with @RestController is capable of handling HTTP requests and automatically serializing the response to the requested format (JSON/XML). The return value of the methods is directly sent as the response body.

Here's an example of a REST controller class using @RestController:

@RestController
public class MyRestController {
    
    @RequestMapping("/api/hello")
    public String hello() {
        return "Hello, World!"; // returns the response body directly
    }
}

Key Differences

  1. Response Handling: With @Controller, the return value of a method is resolved by a view resolver to render the response. In contrast, @RestController directly serializes the return value and sends it as the response body.

  2. Content Negotiation: @Controller allows for content negotiation based on the Accept header, which means it can return different views based on the client's requested format. @RestController always returns the response in the format requested by the client (JSON/XML).

  3. Convenience: @RestController is a convenient choice when building RESTful APIs, as it eliminates the need for additional annotations like @ResponseBody.

Conclusion

In summary, the choice between @Controller and @RestController depends on the type of application you are building. If you are developing a traditional web application that requires view resolution, use @Controller. On the other hand, if you are building a RESTful API that returns JSON or XML responses directly, @RestController is the way to go.

Understanding the differences between these annotations will help you make the right choice and build efficient and scalable Spring applications.

Further Reading

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