@RestController vs @Controller.

@Controller:

• Used for traditional Spring MVC web applications.
• Typically returns a View (HTML/JSP) via a ViewResolver.
• Requires @ResponseBody on methods if you want to return data (JSON/XML).

@RestController:

• A specialized version of @Controller.
• Equivalent to @Controller + @ResponseBody.
• Every method's return value is automatically serialized into the response body (typically JSON).