Difference Between @Controller,@RestController

In Spring Framework, both @Controller and @RestController are used to define controllers, but they serve different purposes. Here’s the key difference:

1. @Controller

• It is used in Spring MVC to define a web controller that handles HTTP requests.
• Typically used for web pages where a view (like JSP, Thymeleaf) is returned.
• Requires @ResponseBody on methods that return JSON or XML instead of a view.

Example:

@Controller
public class MyController {
    @GetMapping("/home")
    public String homePage() {
        return "home"; // Returns the view name (e.g., home.html or home.jsp)
    }

    @GetMapping("/data")
    @ResponseBody
    public String getData() {
        return "Hello, World!"; // Returns raw response (without a view)
    }
}

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2. @RestController

• Introduced in Spring 4.0 as a specialization of @Controller.
• It is a combination of @Controller and @ResponseBody, meaning all methods return data directly (usually JSON or XML).
• No need to use @ResponseBody on each method.

Example:

@RestController
public class MyRestController {

    @GetMapping("/greet")
    public String greet() {
        return "Hello, World!"; // Returns raw response (e.g., JSON or plain text)
    }

    @GetMapping("/user")
    public Map<String, String> getUser() {
        Map<String, String> user = new HashMap<>();
        user.put("name", "John");
        user.put("role", "Admin");
        return user; // Returns JSON response
    }
}

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Key Differences:

Feature	@Controller	@RestController
View Resolution	Returns a view (e.g., JSP, Thymeleaf)	Returns data (JSON/XML)
Implicit @ResponseBody	No (must be added manually)	Yes (applied to all methods)
Use Case	Web applications (MVC)	RESTful APIs

When to Use What?

• Use @Controller if you are building a traditional web application with views.
• Use @RestController if you are developing a REST API that returns JSON/XML.