Difference Between Controller and RestController

Yes, you can use @Controller to build a REST API, but it requires that each method intended to return a response body be explicitly annotated with @ResponseBody. Without @ResponseBody, Spring MVC will interpret the method’s return value as a view name to be resolved, not as data to be written directly to the body of the response. This means extra annotation work compared to using @RestController, which automatically assumes @ResponseBody behavior for all controller methods.

@RestController is specifically designed for services where the response is data (JSON or XML) rather than a rendered view. It simplifies the development of RESTful web services by automatically applying @ResponseBody to all controller methods, eliminating the need for additional annotations to serialize return objects into the response body. If your web application primarily serves as an API that clients consume (e.g., for single-page applications, mobile applications), @RestController is the more efficient and clear choice.

Methods in a class annotated with @Controller that return data directly to the response body must be annotated with @ResponseBody. This approach allows for manual control over the response, including modifying HTTP headers if needed. On the other hand, @RestController combines @Controller and @ResponseBody annotations, which means it automatically serializes the return value to the HTTP response body and handles HTTP headers accordingly, primarily focusing on content type (like application/json). For both annotations, further customization of the response, including headers, can be achieved by returning a ResponseEntity object, allowing for comprehensive control over the response status, headers, and body.