web程序的统一认证实现：filter操作-阿里云开发者社区

现在web程序很多都用到统一认证这东西，刚好看《jsp2.0技术手册》看到这块，看完感觉有点模糊，所以就自己写代码试了一下，花了好长一段时间，原因终于在今天找到了，并且成功解决，但是我并没有因此而感到自豪，因为我越来越感觉自己蠢了，蠢得无可救药。废话不说了，看下面的东西吧：

　　用filter实现统一认证我用了5个页面，分别为：login.jsp,filter2.jsp,filter3.jsp,LoginCheck.java,SessionCheck.java.其中最主要的是SessionCheck.java.另外还需要配置web.xml文件，这个千万不能忘记哦。

　　下面是我的web程序的结构图：

web程序的统一认证实现：filter操作

下面看下各个页面的代码（内含很多注释，方便理解）：

SessionCheck.java:

1 package filter;
2
3 import java.io.IOException;
4 import javax.servlet.Filter;
5 import javax.servlet.FilterChain;
6 import javax.servlet.FilterConfig;
7 import javax.servlet.ServletContext;
8 import javax.servlet.ServletException;
9 import javax.servlet.ServletRequest;
10 import javax.servlet.ServletResponse;
11 import javax.servlet.http.HttpServletRequest;
12 import javax.servlet.http.HttpServletResponse;
13 import javax.servlet.http.HttpSession;
14
15
16 public class SessionCheck implements Filter {
17
18       private ServletContext context;
19       private String targetUri;
20
21       public void destroy() {
22           // TODO Auto-generated method stub
23
24      }
25
26       public void doFilter(
27              ServletRequest request,
28              ServletResponse response,
29              FilterChain chain) throws IOException, ServletException {
30           // TODO Auto-generated method stub
31          HttpServletRequest httpRequest = (HttpServletRequest)request;
32          HttpServletResponse httpResponse = (HttpServletResponse) response;
33           /**
34          * getSession(false)此方法如果得不到session，也不会自动创建一个session
35          *
36          * 插曲：看到getSeesion(false)表示之前没看到过，不知道意思，本能的猜测是：
37          * 如果没有得到sesson，则返回null，如果参数为true，得不到session那就重新创建一个
38          * 因为只是猜测，所以上csdn查了下，结果看到一帖子，说的果断和我的理解相反，
              接着看，下面各种各样的回复，琳琅满目
39          * 当然，在找之前已经用debug验证过了，我的想法只要不是验证方法错了那我的理解肯定是对的
40          * 结果在csdn看到几乎一样的问题，而且一楼回答刚好跟我的完全相反，并且楼主还给了30分，这让我不由的蛋疼了下，
41          * 结论完全相反呀，继续忐忑的往下看，一哥们什么都没解释，直接把关于session的官方文档给拉出来贴着，全英文，还好哥虽然没过6鸡
42          * 但也还是能看懂几个abc的，意思跟我理解一样，忐忑的心终于有点放下了，继续往下看，一看id，俨然是楼主本人，一看内容，我热泪盈眶
43          * 楼主你Y真是好人啊，一楼理解完全相反你Y居然给30分，你妹啊，害得我还犹豫了半天，纳闷了半天，不过还好你出来纠正了你之前的
44          * NC行径，也算是一大进步。
45 */
46          HttpSession session = httpRequest.getSession( false );
47
48           if (session != null ){
49              String passed = (String)session.getAttribute( " passed " );
50               if ( " true " .equals(passed)){
51                  chain.doFilter(httpRequest, httpResponse);
52                   /**
53                  * return 说明filter在执行了chain.doFilter之后会返回来继续执行原先的filter
54                  * 相当于一个递归调用
55                  * return 下面的代码表示执行失败的情况
56 */
57                   return ;
58              } else if ( " passing " .equals(passed)){
59                   /**
60                  * httpRequest.getRequestURL()获取绝对路径
61                  * 例如http://127.0.0.1:8088/webTest/filter1/login.jsp
62                  *
63                  * httpRequest.getRequestURI()获取相对路径。
64                  * /webTest/filter/LoginCheck,其中filter/LoginCheck为jsp页面中form表单的action值
65                  * 对应的Servlet的<url-pattern>要写成/filter/LoginCheck 66 */
67                   if ( " /webTest/filter/LoginCheck " .equals( new String(httpRequest.getRequestURI()))){
68                      chain.doFilter(httpRequest, httpResponse);
69                       return ;
70                  }
71              }
72               /**
73              * 如果之前的filter执行均失败，则说明这个session中的passed认证已经是错误的，必须删除
74 */
75              session.removeAttribute( " passed " );
76          }
77           /**
78          * requestUrl保存当前请求的url
79          * query保存当前请求下的参数
80 */
81          StringBuffer requestUrl = new StringBuffer(httpRequest.getRequestURI());
82          String query = httpRequest.getQueryString();
83           if ( null != query){
84              requestUrl.append(query);
85          }
86           /**
87          * 设置request范围内的originalUri（认证之前的请求地址），用于在login页面获取，并可以通过隐藏参数的形式把这个值传递到LoginCheck
88          * 当登录之后就可以直接转到login认证之前的页面
89 */
90          httpRequest.setAttribute( " originalUri " , new String(requestUrl));
91          httpRequest.getRequestDispatcher(targetUri).forward(httpRequest, httpResponse);
92      }
93
94       public void init(FilterConfig config) throws ServletException {
95           // TODO Auto-generated method stub
96           this .context = config.getServletContext();
97           /**
98          * 获取filter的初始化参数，当需要认证的时候都会跳转到targetUri指定页面，一般都是登录页面
99 */
100           this .targetUri = config.getInitParameter( " targetUri " );
101      }
102
103
104 }

LoginCheck.java:

1 package filter;
2
3 import java.io.IOException;
4 import javax.servlet.ServletException;
5 import javax.servlet.http.HttpServlet;
6 import javax.servlet.http.HttpServletRequest;
7 import javax.servlet.http.HttpServletResponse;
8 import javax.servlet.http.HttpSession;
9
10 public class LoginCheck extends HttpServlet {
11
12       private static final long serialVersionUID = - 4075113258177758412L ;
13
14       protected void doPost(HttpServletRequest request,HttpServletResponse response)
15           throws IOException,ServletException{
16          String user = request.getParameter( " user " );
17          String pwd = request.getParameter( " pwd " );
18          String targetUri = request.getParameter( " originalUri " );
19
20           if ( ! " LH123 " .equals(user) || ! " 123LH " .equals(pwd)){
21              System.out.println( " 认证失败 " );
22               throw new ServletException( " 认证失败 " );
23          }
24           /**
25          * 认证成功的情况
26 */
27          HttpSession session = request.getSession();
28          session.setAttribute( " passed " , " true " );
29          request.setAttribute( " user " , user);
30          request.setAttribute( " pwd " , pwd);
31           if ( ! "" .equals(targetUri)){
32               /**
33              * SessionCheck中保存入的之前的请求的uri的格式为：/webTest/filter/filter3.jsp
34              * 而getRequestDispatcher这种方法传递过去的是一个相对路径，不需要再加上/webTest
35              * 这个方法可以把页面表单的值传递到另外一个页面，而不只是纯粹的跳转
36 */
37              request.getRequestDispatcher(targetUri.substring( 8 )).forward(request, response);
38          } else {
39              response.sendRedirect( " http://127.0.0.1:8088/webTest/filter1/filter2.jsp " );
40          }
41      }
42 }

<% @ page language = " java " import = " java.util.* " pageEncoding = " UTF-8 " %>
<% @ taglib prefix = " c " uri = " http://java.sun.com/jsp/jstl/core " %>
<%
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 > 测试filter </ 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" >
         
    </ head >

< body >
    < c:set var = "passed" value = "passing" scope = "session" >
    </ c:set >
     < form action = "filter/LoginCheck" method = "post" >
         < table >
             < tr >
                 < th > 用户账号： </ th >
                 < td >< input type = "text" name = "user" value = "" /></ td >
             </ tr >
             < tr >
                 < th > 登录密码： </ th >
                 < td >< input type = "password" name = "pwd" value = "" /></ td >
             </ tr >
                 < th >
                     < input type = "hidden" name = "originalUri" value = "${requestScope.originalUri}" />
                 </ th >
             < tr >
                < td >< input type = "submit" name = "submit" value = "提交" /></ td >             </ tr >
         </ table >
     </ form >
   </ body >
</ html >

filter2.jsp

1 <% @ page language = " java " import = " java.util.* " pageEncoding = " UTF-8 " %>
2 <% @ taglib prefix = " c " uri = " http://java.sun.com/jsp/jstl/core " %>
3 <%
4 String path = request.getContextPath();
5 String basePath = request.getScheme() + " :// " + request.getServerName() + " : " + request.getServerPort() + path + " / " ;
6 %>
7
8 <! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
9 < html >
10    < head >
11      < base href ="<%=basePath%>" >
12
13      < title > My JSP 'filter2.jsp' starting page </ title >
14
15      < meta http-equiv ="pragma" content ="no-cache" >
16      < meta http-equiv ="cache-control" content ="no-cache" >
17      < meta http-equiv ="expires" content ="0" >
18      < meta http-equiv ="keywords" content ="keyword1,keyword2,keyword3" >
19      < meta http-equiv ="description" content ="This is my page" >
20       23 24    </ head > 25   26    < body >
27       HHHHH
28
29    </ body >
30 </ html >

filter3.jsp

1 <% @ page language = " java " import = " java.util.* " pageEncoding = " UTF-8 " %>

2 <% @ taglib prefix = " c " uri = " http://java.sun.com/jsp/jstl/core " %>

3 <%

4 String path = request.getContextPath();

5 String basePath = request.getScheme() + " :// " + request.getServerName() + " : " + request.getServerPort() + path + " / " ;

6 % >

8 <! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >

9 < html >

10 < head >

11 < base href ="<%=basePath%>" >

13 < title > My JSP 'filter3.jsp' starting page </ title >

15 < meta http-equiv ="pragma" content ="no-cache" >

16 < meta http-equiv ="cache-control" content ="no-cache" >

17 < meta http-equiv ="expires" content ="0" >

18 < meta http-equiv ="keywords" content ="keyword1,keyword2,keyword3" >

19 < meta http-equiv ="description" content ="This is my page" >

20 <!-- 21 <link rel="stylesheet" type="text/css" href="styles.css">

22 -->

24 </ head >

26 < body >

27 < c:out value ="${user}" ></ c:out > < br >

28 < c:out value ="${pwd}" ></ c:out > < br >

29 </ body >

30 </ html >

web.xml:　　

1 <? xml version="1.0" encoding="UTF-8" ?>

2 < web-app version ="2.5"

3 xmlns ="http://java.sun.com/xml/ns/javaee"

4 xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"

5 xsi:schemaLocation ="http://java.sun.com/xml/ns/javaee

6 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" >

7 < servlet >

8 < servlet-name > LoginCheck </ servlet-name >

9 < servlet-class > filter.LoginCheck </ servlet-class >

10 </ servlet >

11 < servlet-mapping >

12 < servlet-name > LoginCheck </ servlet-name >

13 < url-pattern > /filter/LoginCheck </ url-pattern >

14 </ servlet-mapping >

16 < filter >

17 < filter-name > SessionCheck </ filter-name >

18 < filter-class > filter.SessionCheck </ filter-class >

19 < init-param >

20 < param-name > targetUri </ param-name >

21 < param-value > /filter1/login.jsp </ param-value >

22 </ init-param >

23 </ filter >

24 < filter-mapping >

25 < filter-name > SessionCheck </ filter-name >

26 < url-pattern > /* </ url-pattern >

27 </ filter-mapping >

28 < welcome-file-list >

29 < welcome-file > index.jsp </ welcome-file >

30 </ welcome-file-list >

31 </ web-app >

代码就是以上这些，效果：

　　直接访问filter3.jsp，将会跳转到login.jsp，当通过用户认证之后就会跳转到filter3.jsp，这个功能很好用，比如csdn下载东西，你没有登录直接点击下载，系统会让你先登录，登录完了可以直接进入到下载页面，不需要再进行其他的操作。

　　直接访问login.jsp，通过认证以后会跳转到默认的页面，比如csdn，直接登录的话，会跳转到csdn的首页

　　注意：此例子的用户名和密码分别为 LH123和123LH，只有用这对组合才可以通过认证，才得以测试本例子。

本文转自 wws5201985 51CTO博客，原文链接：http://blog.51cto.com/wws5201985/735592，如需转载请自行联系原作者

web程序的统一认证实现：filter操作

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