springMVC的handler都有哪些类型

今天药忘吃喽~ 2022-12-16 06:15 186阅读 0赞

## 1：@ReqeustMapping ##

这是当前我们使用最多的一种方式，是以方法作为handler，可能定义如下：

@Controller
    @RequestMapping("/test")
    public class FileUploadController { 
    
    	@RequestMapping("/file-upload")
    	public ModelAndView upload(@RequestParam(value = "file", required = true)MultipartFile file,
    			HttpServletRequest request, HttpSession session) { 
    	...
    	}
    }

对应的handleradpater是`org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter`。

## 2：Conroller接口 ##

实现`org.sprignframework.web.servlet.mvc.Controller`，只有一个方法，源码如下：

@FunctionalInterface
    public interface Controller { 
    	@Nullable
    	ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception;
    }

可能定义如下：

@Component(value = "/my_bean_name_url_handler")
    public class MyBeanNameUrlHandlerController implements Controller { 
    	@Override
    	public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception { 
    		String msg = "this is my bean name url handler";
    		System.out.println(msg);
    		response.getWriter().write(msg);
    		return null;
    	}
    }

对应的handleradapter是`org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter`。

## 3：HttpRequestHandler接口 ##

实现`org.springframework.web.HttpReqeustHandler`接口，只有一个方法，源码如下：

@FunctionalInterface
    public interface HttpRequestHandler { 
    	void handleRequest(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException;
    }

可能使用如下：

@Component("/login")
    public class LoginController implements HttpRequestHandler { 
        @Override
        public void handleRequest(HttpServletRequest request,
        		HttpServletResponse response)
        		throws ServletException, IOException { 
            System.out.println("login...");
            response.getWriter().write("login ...");
        }
    }

对应的handleradapter是`org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter`。

## 4：HttpServlet类 ##

实现`javax.servlet.http.HttpServlet`类，可能定义如下：

public class LastModifiedServlet extends HttpServlet { 
    	private static Long count = -1L;
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    			throws ServletException, IOException { 
    		System.out.println("req...");
    		count = System.currentTimeMillis();
    		resp.getWriter().write("hello" + count);
    	}
    
    	@Override
    	protected long getLastModified(HttpServletRequest req) { 
    		return count;
    	}
    }

对应的handleradpater是`org.springframework.web.servlet.handler.SimpleServletHandlerAdapter`。