JavaBean四个作用域范围

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

 

 

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" >

         <!--

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

        -->

 

   </ 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" >

         <!--

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

        -->

 

   </ head >

 

   < body >

     < jsp:useBean  id = "myUsers"  class = "com.po.Users"  scope = "page" />

     < h1 > setProperty动作元素 </ h1 >

     < hr >

    <!--根据表单自动匹配所有的属性 -->

    <%--

   <jsp:setProperty name="myUsers" property="*"/> 

   --%>

    <!--根据表单匹配所有部分的属性 -->

    <%--

   <jsp:setProperty name="myUsers" property=" username "/> 

   --%>

    <!--根表单无关，通过手工赋值给属性 -->

    <%--

   <jsp:setProperty name="myUsers" property=" username " value=" lisi "/>

   <jsp:setProperty name="myUsers" property="password" value="888888"/>

   --%>

    <!--通过URL传参数给属性赋值 -->

    < jsp:setProperty  name = "myUsers"  property = "username" />

    < jsp:setProperty  name = "myUsers"  property = "password"  param = "mypass" />

    <!-- 使用传统的表达式方式来获取用户名和密码 -->

    <%--    

       用户名：<%=myUsers.getUsername() %><br>

       密码：<%=myUsers.getPassword() %><br>

   --%>

    <!-- 使用getProperty方式来获取用户名和密码 -->

      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" >

<!--

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

        -->

 

</ 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 >

         <!-- 使用内置对象获取用户名和密码 -->

         < hr >

         <%--

       用户名：<%=((Users)application.getAttribute("myUsers")).getUsername()%><br>

       密码：<%=((Users)application.getAttribute("myUsers")).getPassword() %><br>

   --%>

         <%--

       用户名：<%=((Users)session.getAttribute("myUsers")).getUsername()%><br>

       密码：<%=((Users)session.getAttribute("myUsers")).getPassword() %><br>

   --%>

         <%--

       用户名：<%=((Users)request.getAttribute("myUsers")).getUsername()%><br>

       密码：<%=((Users)request.getAttribute("myUsers")).getPassword() %><br>

   --%>

         <%

                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