javaBean基础和EL表达式

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useBean里面的id和setProperty里面的name是同一个类的对象

内部运用java反射原理，名字最好保持一致。setProperty里面的usernaem实际上是调用setuserName()方法反射

param=“*”

<%@ page language="java" import="java.util.Date" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>         <title>My JSP '1.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">      </head>    <body>   <jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page"></jsp:useBean>   <jsp:setProperty property="username" name="person" value="username"/>   <jsp:setProperty property="password" name="person" value="password"/>   <jsp:setProperty property="birthday" name="person" value="<%=new Date() %>"/>      <%=person.getBirthday() %>  </body></html>

EL表达式

$美国人眼里光有钱

获取当前文本应用的名称在jsp里面是这样

${pageCintext.request.cintextPath

List看成数组形式

Map看成类形式

EL表达式其实是pageContext.findAttribute("data")从这四个域里面（ page request session application）依次查找获取

<%@ page language="java" import="java.util.Date" pageEncoding="UTF-8"%><%@page import="cn.itcast.domain.Person"%><%@page import="cn.itcast.domain.Address"%><%@page import="java.util.List"%><%@page import="java.util.ArrayList"%><%@page import="java.util.Map"%><%@page import="java.util.HashMap"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>         <title>My JSP '1.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">      </head>    <body><%String data="my data";request.setAttribute("data",data);%>${data } <%--pageContext.findAttribute("data") page request session application --%><br/><%Person p=new Person();p.setName("namenamename");request.setAttribute("p",p);%>${p.name }<%Person p1=new Person();Address a=new Address();a.setCity("huang gang");p1.setAddress(a);request.setAttribute("p1",p1);%>${p1.address.city }<%List list=new ArrayList();list.add(new Address("上海"));list.add(new Address("北京2"));list.add(new Address("武汉"));request.setAttribute("list",list);%>${list[1].city } <%--北京2 --%><%Map map=new HashMap();map.put("aa",new Address("上海"));map.put("bb",new Address("北京2"));map.put("cc",new Address("武汉"));map.put("111",new Address("南京"));request.setAttribute("map",map);%>${map.aa.city } <%--上海 --%>${map["111"].city } <%--南京 ,通常用点号，点号取不出来用[]--%>  ${pageContext.request.contextPath }<%--/day09  --%>  </body></html>