@Controller vs @RestController

 In Spring Framework (especially Spring MVC and Spring Boot), both @Controller and @RestController are used to define web controllers, but they behave differently in how they handle responses.

✅ 1. @Controller (Classic MVC Controller)

• Returns views (like JSP, Thymeleaf).

• Used in traditional web applications.

• You typically return a view name, not the response body.

• To return data (like JSON), you need to use @ResponseBody.

E.g.,

@Controller

public class MyController {

    @GetMapping("/hello")

    public String hello(Model model) {

        model.addAttribute("message", "Hello from Controller");

        return "hello"; // returns view "hello.html" or hello.jsp

    }

    @GetMapping("/api/data")

    @ResponseBody

    public String getData() {

        return "This is raw data"; // returns raw response

    }

}

✅ 2. @RestController (Spring 4+ Shortcut for REST APIs)

• A convenient annotation for RESTful services.

• Equivalent to @Controller + @ResponseBody on every method.

• Returns JSON or XML directly (default: JSON).

• No view resolution.

E.g., 

@RestController

public class MyRestController {

    @GetMapping("/hello")

    public String hello() {

        return "Hello from RestController"; // returned directly as response body

    }

    @GetMapping("/json")

    public Map<String, Object> json() {

        return Map.of("status", "success", "code", 200); // returns as JSON

    }

}

🔍 Comparison Table:

Feature	@Controller	@RestController
Purpose	Traditional MVC (Web UI)	REST APIs (returning data)
View Resolver Used?	Yes	No
JSON Response Default?	No (need @ResponseBody)	Yes
Introduced In	Spring 2.5	Spring 4.0
Best Use Case	Web apps with HTML/JSP/Thymeleaf	RESTful web services

✅ When to Use What?

If you're building...	Use
A full web UI (JSP, Thymeleaf)	@Controller
A JSON/REST API backend	@RestController