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一、拦截器

1、定义

Spring Web MVC 的处理器拦截器类似于Servlet开发中的过滤器Filter。

用于对处理器进行预处理和后处理。

2、拦截器定义，创建拦截器，创建第一个拦截器

实现HandlerInterceptor接口，如下

（1）创建MyInterceptor实现HandlerInterceptor接口

（2）完善MyInterceptor方法：为分析实现接口三个方法不同的作用做准备

package com.itzheng.springmvc.interceptor;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;/* * 自定义拦截器 */public class MyInterceptor implements HandlerInterceptor {
   	@Override	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)			throws Exception {
   		System.out.println("MyInterceptor.afterCompletion");	}	@Override	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)			throws Exception {
   		System.out.println("MyInterceptor.postHandle");	}	@Override	public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
   		System.out.println("MyInterceptor.preHandle");		//true放行，false拦截		return true;	}}

3、配置拦截器

修改springmvc.xml

4、ItemController当中的itemList当中的内容

@RequestMapping(value = {
    "itemList", "itemList2" })	public ModelAndView itemList() {
   		ModelAndView mav = new ModelAndView();		List
   
     itemList = itemService.getItemList();		mav.addObject("itemList", itemList);		// mav.setViewName("/WEB-INF/jsp/itemList.jsp");		mav.setViewName("itemList");		System.out.println("ItemController.itemList.......");		return mav;	}
   

5、运行并测试拦截器

(1)调节日志输出级别

(2)访问:

(3)查看运行结果

package com.itzheng.springmvc.interceptor;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;/* * 自定义拦截器 */public class MyInterceptor implements HandlerInterceptor {
   	//afterCompletion方法执行后被执行	//处理异常，清理资源，记录日志等操纵	@Override	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)			throws Exception {
   		System.out.println("MyInterceptor.afterCompletion");	}	//方法执行之后，返回ModelAndView之前被执行	//页面的公用参数等操纵	@Override	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)			throws Exception {
   		System.out.println("MyInterceptor.postHandle");	}		//进入方法之前被执行	//登录拦截， 权限校验等等	@Override	public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
   		System.out.println("MyInterceptor.preHandle");		//true放行，false拦截		return true;	}}

6、创建第二个拦截器

（1）复制上述拦截器

package com.itzheng.springmvc.interceptor;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;/* * 自定义拦截器 */public class MyInterceptor2 implements HandlerInterceptor {
   	//afterCompletion方法执行后被执行	//处理异常，清理资源，记录日志等操纵	@Override	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)			throws Exception {
   		System.out.println("MyInterceptor2.afterCompletion");	}	//方法执行之后，返回ModelAndView之前被执行	//页面的公用参数等操纵	@Override	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)			throws Exception {
   		System.out.println("MyInterceptor2.postHandle");	}		//进入方法之前被执行	//登录拦截， 权限校验等等	@Override	public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
   		System.out.println("MyInterceptor2.preHandle");		//true放行，false拦截		return true;	}}

（2）配置拦截器

（3）运行项目

（4）设置第一个拦截器不放行

（5）设置第一个拦截器放行，第二个不放行

（6）两个都放行

二、拦截器案例应用，登录拦截器

1、创建login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%>			
   				
   
    		用户名：
    
    
		密码：
    
    
		
    	
   

2、创建新的控制器

package com.itzheng.springmvc.controller;import javax.servlet.http.HttpSession;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;/* * 用户请求处理器 */@Controller@RequestMapping("user")public class UserController {
   	//跳转登录的方法	@RequestMapping("toLogin")	public String toLogin() {
   		return "login";	}	//处理登录的方法	@RequestMapping("login")	public String login(String username,String password,HttpSession session) {
   		if(username.equals("admin")) {
   			session.setAttribute("username", username);			return "redirect:/itemList.action";		}		return "login";	}}

3、创建LoginInterceptor拦截器

package com.itzheng.springmvc.interceptor;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;/* * 登录拦截器 */public class LoginInterceptor implements HandlerInterceptor {
   	//afterCompletion方法执行后被执行	//处理异常，清理资源，记录日志等操纵	@Override	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)			throws Exception {
   	}	//方法执行之后，返回ModelAndView之前被执行	//页面的公用参数等操纵	@Override	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)			throws Exception {
   	}	//进入方法之前被执行	//登录拦截， 权限校验等等	@Override	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
   		//判断用户有没有登录		Object object = request.getSession().getAttribute("username");		if(object == null) {
   			response.sendRedirect(request.getContextPath()+"/user/toLogin.action");		}		//true放行，false拦截		return true;	}}

4、配置拦截器

5、运行测试

访问

结果跳转到了登录页面

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