JavaBean四个作用域范围

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一 说明
使用useBeans的scope属性可以用来指定javabean的作用范围。
 
二 四个作用范围

JavaBean四个作用域范围_第1张图片
 
 
三 代码
1、login.jsp
<%@  page  language = "java"  import = "java.util.*"  contentType = "text/html; charset=utf-8"  %>
<%
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 > My JSP 'login.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" >
        
 
   head >
 
   < body >
     < h1 > 系统登录 h1 >
     < hr >
     < form  name = "loginForm"  action = "dologin.jsp?mypass=999999"  method = "post" >
       < table >
         < tr >
           < td > 用户名: td >
           < td >< input  type = "text"  name = "username"  value = "" /> td >
         tr >
         < tr >
           < td > 密码: td >
           < td >< input  type = "password"  name = "password"  value = "" /> td >
         tr >
         < tr >
           < td  colspan = "2"  align = "center" >< input  type = "submit"  value = "登录" /> td >
         
         tr >
       table >
     form >
   body >
html >
2、dologin.jsp
<%@  page  language = "java"  import = "java.util.*"  contentType = "text/html; charset=utf-8" %>
<%
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 > My JSP 'dologin.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" >
        
 
   head >
 
   < body >
     < jsp:useBean  id = "myUsers"  class = "com.po.Users"  scope = "page" />
     < h1 > setProperty动作元素 h1 >
     < hr >
   
    <%--
    
   --%>
   
    <%--
   username "/> 
   --%>
   
    <%--
   username " value=" lisi "/>
  
   --%>
   
    < jsp:setProperty  name = "myUsers"  property = "username" />
    < jsp:setProperty  name = "myUsers"  property = "password"  param = "mypass" />
   
    <%--    
       用户名:<%=myUsers.getUsername() %>
       密码:<%=myUsers.getPassword() %>
   --%>
   
      用户名: < jsp:getProperty  name = "myUsers"  property = "username" />  < br >
      密码: < jsp:getProperty  name = "myUsers"  property = "password" />< br >
    < br >
    < br >
 
       < a  href = "testScope.jsp" > 测试 javabean 的四个作用域范围 a >
 
       <%
         request.getRequestDispatcher( "testScope.jsp" ).forward(request, response);
       %>
 
   body >
html >
3、testScope.jsp
<%@  page  language = "java"  import = "java.util.*"
         contentType = "text/html; charset=utf-8" %>
<%@  page  import = "com.po.Users" %>
<%
        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 > My JSP 'testScope.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" >
 
head >
 
< body >
         < h1 > Javabean 的四个作用域范围 h1 >
         < hr >
         < jsp:useBean  id = "myUsers"  class = "com.po.Users"  scope = "page"  />
        用户名: < jsp:getProperty  name = "myUsers"  property = "username"  />< br >  密码: < jsp:getProperty
                 name = "myUsers"  property = "password"  />< br >
        
         < hr >
         <%--
       用户名:<%=((Users)application.getAttribute("myUsers")).getUsername()%>
       密码:<%=((Users)application.getAttribute("myUsers")).getPassword() %>
   --%>
         <%--
       用户名:<%=((Users)session.getAttribute("myUsers")).getUsername()%>
       密码:<%=((Users)session.getAttribute("myUsers")).getPassword() %>
   --%>
         <%--
       用户名:<%=((Users)request.getAttribute("myUsers")).getUsername()%>
       密码:<%=((Users)request.getAttribute("myUsers")).getPassword() %>
   --%>
         <%
                String username =  "" ;
                String password =  "" ;
                 if  (pageContext.getAttribute( "myUsers" ) !=  null ) {
                        username = ((Users) pageContext.getAttribute( "myUsers" ))
                                        .getUsername();
                        password = ((Users) pageContext.getAttribute( "myUsers" ))
                                        .getPassword();
                }
         %>
 
        用户名: <%= username %> < br >  密码: <%= password %> < br >
 
 
 
body >
html >
 
四 测试结果

JavaBean四个作用域范围_第2张图片
 

 

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