通常我们在点击某个按钮的时候，对某个对象进行操作，是需要登陆才能做的，这时候就需要一个拦截器对某个方法进行拦截，
比如你在一个图书管理中心中你要借书，这时候你就会被要求出示借书证，管理员才能借书给你。而拦截器就具有这样的功能
：游客点击借书按钮-->后台拦截器拦截该方法-->判断你是否登陆-->已经登陆-->允许操作-->没登陆-->请登陆-->允许操作
代码如下：
UserFiler.java
package com.utis.filter; import java.io.IOException; import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession; public class UserFiter implements Filter{ public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub } public void destroy() {
// TODO Auto-generated method stub } public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//获取HttpSession对象，判断是否登陆
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
HttpSession session = req.getSession(); if(session.getAttribute("model")==null){
//非法访问，没有登陆，跳转到登陆页面
session.setAttribute("error", "非法访问");
// 保存客户想要去的地址, 登录成功后则直接跳转,而不是到首页
String goURL = req.getServletPath();//(获取到地址不包括参数)
//判断参数是否为空，不null就获取参数
if(req.getQueryString()!=null){
goURL+="?"+req.getQueryString();
}
session.setAttribute("goURL", goURL);
res.sendRedirect(req.getContextPath() + "/user/userLogin.jsp");
}else{
// 如果有下一个过滤器则跳转到下一个过滤器否则目标页面
chain.doFilter(request, response);
}
} }
web.xml
<filter>
<!-- 配置在web.xml的拦截器，在容器启动的时候一起启动 -->
<filter-name>userFilter</filter-name>
<filter-class>com.utis.filter.UserFiter</filter-class>
</filter>
<filter-mapping>
<filter-name>userFilter</filter-name>
<url-pattern>/book/*</url-pattern>
</filter-mapping>
UserContrller.java
/**
* 用户登陆功能
* @return
*/
@RequestMapping(value="login",method=RequestMethod.POST)
public ModelAndView userLogin(@Valid User user,HttpServletRequest request,HttpServletResponse response){
Map<String, Object> maplist = new HashMap<String, Object>();
HttpSession session = request.getSession();
User model = userService.findUser(user);
if(model != null && !model.equals("")){
session.setAttribute("model", model);
maplist.put("model", model);
return new ModelAndView("index","maplist",maplist); }else{
request.setAttribute("message", "用户或密码错误!");
return new ModelAndView("user/userLogin");
}
}
userLogin.jsp
<html>
<head>
<title>登陆页面</title>
</head> <body>
<center>
<h1>登陆页面</h1>
<table>
<form action="login" method="post">
用户名:<input type="text" class="username" name="username"/><br/>
密 码:<input type="password" class="password" name="password"/><br/>
<input type="submit" value="登陆"><br/>
</form>
${message}
</table>
</center>
</body>
</html>
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>首页</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head> <body> <CENTER>
<h1>图书首页</h1>
<c:choose>
<c:when test="${empty sessionScope.model}">
<a href="<%=basePath%>user/userLogin.jsp">登陆</a>
<a href="<%=basePath%>user/userRegister.jsp">注册</a>
</c:when>
<c:otherwise>
欢迎使用图书管理系统：${sessionScope.model.username }
</c:otherwise>
</c:choose> <c:if test="${booklist ne '' && booklist != null}">
<!-- 作为隐藏的传递参数 -->
<table border="1"
style="border-collapse: collapse; border-color: blue;">
<!-- 表头 -->
<tr>
<th>
书名
</th>
<th>
出版社
</th>
<th>
是否可借
</th>
<th>
数量
</th>
<th>
操作
</th>
</tr>
<!-- 显示数据列表 -->
<c:forEach items="${booklist}" var="book">
<tr>
<td>
${book.bookname }
</td>
<td>
${book.chubanshe }
</td>
<td>
${book.state }
</td>
<td>
${book.number }
</td>
<td>
<a
href="book/borrowBook?bookid=${book.bookid }&userid=${sessionScope.model.userid }">借书</a>
</td>
</tr>
</c:forEach> <!-- 其他操作 -->
<tr>
<td colspan="7">
<a href="#">添加</a>
</td>
</tr>
</table>
</c:if>
</CENTER>
</body>
</html>
初始化数据
IniDataListener.java
package com.booksys.listener; import java.util.Timer; import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener; import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils; import com.booksys.service.BookService;
import com.utis.util.GoodsTimerTask;
/**
* 该类的主要作用是用于加载index首页的方法，查询数据，显示首页
* @author chunyu
*
*/
public class InitDataListener implements ServletContextListener{ private BookService bookService;
private GoodsTimerTask goodsTimerTask; public void contextDestroyed(ServletContextEvent sce) { } public void contextInitialized(ServletContextEvent event) {
ApplicationContext context = null;
//通过spring的web工具类来加载spring容器(配置文件)，并且调用某个类来做某事
context=WebApplicationContextUtils.getWebApplicationContext(event.getServletContext());
//1、获取bookservice
bookService = (BookService) context.getBean("bookService");
goodsTimerTask = (GoodsTimerTask) context.getBean("goodsTimerTask");
//2、查询所有图书
event.getServletContext().setAttribute("booklist", bookService.findBook());
//将Application内置对象，传入到goodsTimerTask查询的数据对象中
goodsTimerTask.setApplication(event.getServletContext());
// 设置时间任务,每隔一段时间加载首页的商品信息, 此线程必须设置守护线程, 主线程停止的时候此线程也要停止
new Timer(true).schedule(goodsTimerTask, 0,1000*60); } }
web.xml
<!-- 初始化首页信息（查询）监听器 -->
<listener>
<listener-class>
com.booksys.listener.InitDataListener
</listener-class>
</listener>
时间戳：用于自动调用查询方法，更新首页数据显示
GoodsTimerTask.java
package com.utis.util; import java.util.List;
import java.util.TimerTask; import javax.annotation.Resource;
import javax.servlet.ServletContext; import org.springframework.stereotype.Component; import com.booksys.domain.Book;
import com.booksys.service.BookService; @Component("goodsTimerTask")
public class GoodsTimerTask extends TimerTask { //传入Application内置对象
private ServletContext application; public void setApplication(ServletContext application) {
this.application = application;
} //获取业务逻辑类
@Resource
private BookService bookService=null; @Override
public void run() {
System.out.println("GoodsTimerTask.run()");
//首页加载图书数据信息
List<Book> booklist = bookService.findBook();
//将list集合数据存储到app内置对象中，在inde前台通过循环查询出来
application.setAttribute("booklist", booklist);
}
}