el表达式的功能3：从域对象中获取数据
写一段java代码，往域对象中存数据
<%
pageContext.setAttribute("a",100);
request.setAttribute("b",200);
session.setAttribute("c",300);
application.setAttribute("d",400);
%>
java代码的方式从域对象中获取数据
<%=pageContext.getAttribute("a") %>
<%=request.getAttribute("b") %>
<%=session.getAttribute("c") %>
<%=application.getAttribute("d") %>
el表达式的方式从域对象中获取数据
${a} ${b} ${c} ${d}
el表达式另外一种获取域对象数据的方式
${pageScope.a} ${requestScope.b} ${sessionScope.c} ${applicationScope.d}
一旦用el表达式指定从哪个域中取数据，定要保证name是正确的
${pageScope.aa}
<%@page pageEncoding="utf-8"%>
el表达式的功能3：从域对象中获取数据
<%
pageContext.setAttribute("a",100);
request.setAttribute("b",200);
session.setAttribute("c",300);
application.setAttribute("d",400);
%>
<%=pageContext.getAttribute("a") %>
<%=request.getAttribute("b") %>
<%=session.getAttribute("c") %>
<%=application.getAttribute("d") %>
${a} ${b} ${c} ${d}
${pageScope.a} ${requestScope.b} ${sessionScope.c} ${applicationScope.d}
--${pageScope.aa}
