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  }

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" >

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

    </ 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 >

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      <!-- 21     <link rel="stylesheet" type="text/css" href="styles.css">22  --> 23 24    </ head > 25   26    < body >

27       HHHHH

28      

29    </ body >

30  </ html >

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 'filter3.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      <!-- 21     <link rel="stylesheet" type="text/css" href="styles.css">

22  -->

23

24    </ head >

25  

26    < body >

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

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

29    </ body >

30  </ html >

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 >

15    

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 >