Spring-boot读书笔记一@Controller Annotation

@Controller is a Spring Framework annotation that marks a class as a web controller component.

Purpose

• Web Layer Component: Identifies classes that handle HTTP requests in Spring MVC applications
• Stereotype Annotation: Specialization of @Component for presentation layer

Key Features

• Automatic Detection: Classes annotated with @Controller are automatically detected during component scanning
• Bean Registration: Automatically registered as Spring beans in the application context
• Request Handling: Works with @RequestMapping and related annotations to handle web requests

Basic Usage

@Controller
public class HomeController {
    
    @RequestMapping("/home")
    public String home() {
        return "home"; // Returns view name
    }
}

Return Types
Controllers can return:

• String: View name for template resolution
• ModelAndView: View name with model data
• ResponseEntity: Full HTTP response control
• @ResponseBody: Direct response body content

Related Annotations

• @RestController: Combines @Controller + @ResponseBody
• @RequestMapping: Maps HTTP requests to handler methods
• @GetMapping/@PostMapping: HTTP method-specific mappings

Difference from @RestController

• @Controller: Returns view names (for template rendering)
• @RestController: Returns data directly as HTTP response body

Component Scanning
Requires @ComponentScan or @SpringBootApplication to be detected:
@ComponentScan(basePackages = "com.example.controllers")

Controllers handle the presentation layer logic and coordinate between the service layer and view templates.