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SpringMvc的简单入门(四)之拦截器

程序员文章站 2022-07-09 18:03:42
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一.过滤器与拦截器的区别

1.当浏览器访问Tomcat的时候过滤器会拦截资源，过滤器什么资源都拦截，过滤器在拦截器之前，是用来拦截servlet的

2.DispatcherServlet*处理器 在所有的action实现之前的拦截，拦截器拦截的是action，拦截器是类似过滤器的一种资源，是SpringMvc内置实现的，必须实现一个接口HandlerInterceptor

二.自定义拦截器

拦截器原理

SpringMvc的简单入门(四)之拦截器

在mvc-servlet.xml中配置拦截器

 <!-- 该拦截器用于拦截URL上参数  -->
  <mvc:interceptors>
  	
  	<!-- 自定义拦截器 -->
  	<mvc:interceptor>
  		<!-- 要拦截的资源 path=/*拦截所有-->
  		<mvc:mapping path="/tm"/>
  		<!-- 实现拦截器类的路径 -->
  		<bean class="springmvc.less05.controller.MyInterController"></bean>
  	</mvc:interceptor>
  </mvc:interceptors>
实现接口HandlerInterceptor 

package springmvc.less05.controller;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
public class MyInterController implements HandlerInterceptor {
	//在action执行完拦截
	public void afterCompletion(HttpServletRequest request,
			HttpServletResponse response, Object handler, Exception ex)
			throws Exception {
		// TODO Auto-generated method stub

	}
	//在action执行之后拦截
	public void postHandle(HttpServletRequest request,
			HttpServletResponse response, Object handler,
			ModelAndView modelAndView) throws Exception {
		// TODO Auto-generated method stub

	}
	//在action执行之前就拦截
	public boolean preHandle(HttpServletRequest request,
			HttpServletResponse response, Object handler) throws Exception {
		//获取设置的UUID值
		String myToken= request.getParameter("token");
		//获取session
		Object myToken1= request.getSession().getAttribute("token");
		//true 让拦截器过 false则是拦下
		//判断是否是重复提交，如何参数有值就是重复提交,需要验证重复提交
		if(myToken!=null){
			//如果session==null就是重复提交返回false拦截
			if(myToken1==null){
				return false;
			}else{
				//如果设置的UUID和session相等就不拦截action，清掉session的值
				if(myToken.equals(myToken1)){
					request.getSession().removeAttribute("token");
					return true;
				}else{
					return false;
				}
			}
		}else{
			return true;
		}
	}

}

action

package springmvc.less05.controller;

import java.io.OutputStream;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import springmvc.less05.dao.MoneyDaoImpl;
@Controller
public class InterController {
	@RequestMapping(value="/inter",method=RequestMethod.GET)
	public String quert(OutputStream os)throws Exception{
		os.write("hello".getBytes());
		return null;
	}
	@Autowired
	MoneyDaoImpl mdi;
	@RequestMapping(value="/tm",method=RequestMethod.GET)
	public String quer(Integer money,OutputStream os)throws Exception{
		//根据前台传过来的金额进行扣钱
		mdi.updateMoney(money);
		//显示剩余的金钱
		os.write(("lostedmoney is:"+mdi.selectMoney()).getBytes());
		return null;
	}
}

业务逻辑层 

package springmvc.less05.dao;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class MoneyDaoImpl {
	@Autowired
	JdbcTemplate jdbc;
	//修改金额
	public void updateMoney(int money){
		String sql="update mymoney set lostedmoney=lostedmoney-"+money+" where usid=1";
		jdbc.execute(sql);
	}
	//查询剩余金额
	public int selectMoney(){
		String sql="select lostedmoney from mymoney where usid=1";
		Integer lostedMoney=jdbc.queryForObject(sql,Integer.class);
		return lostedMoney;	
	}
	
}
前台页面 

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@taglib tagdir="/WEB-INF/tags" prefix="my"%><!-- 引入防重复提交标签 -->
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'money.jsp' starting page</title>
    
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>
  
  <body>
   <form action="${pageContext.request.contextPath}/tm">
   	扣钱:<input name ='money'>
   	<!-- 引入防重复提交标签 -->
   	<my:token></my:token>
   	<input type="submit" name="扣钱">
   </form>
  </body>
</html>

三.防重复提交

防重复提交原理

SpringMvc的简单入门(四)之拦截器

 在WEB-INF设置标签 设置隐藏表单域和给session设值

<%@ tag language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@attribute name="tokename" required="false" %>
<%
String ranStr=UUID.randomUUID().toString();
String key=(tokename==null?"token":tokename);
session.setAttribute(key,ranStr);
%>
<input type='hidden' name='<%=key %>' value='<%=ranStr %>'/>


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