EL表达式和JSTL标签快速入门

来源：互联网发布：网络平台公司组织架构编辑：程序博客网时间：2024/04/28 05:07

jsp代码：

<%@ page language="java" import="cn.itcast.domain.*,java.util.*" pageEncoding="UTF-8"%><%@page import="java.util.ArrayList"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>el表达式</title>  </head>    <body>    <!-- 数据以普通方式带来 --><%String data = "abcd";request.setAttribute("data",data); %>  ${data }<%-- pageContext.findAttribute("data") page request session application --%><br/><!-- 数据存在bean里面带来 --><%Person p = new Person();p.setName("aaaa");request.setAttribute("person",p); %> ${person.name } <br/><!-- 数据存在复杂bean里面带来 --><%Person p1 = new Person();Address a = new Address();a.setCity("上海");p1.setAddress(a);request.setAttribute("p1",p1); %> ${p1.address.city } <br/><!-- 数据存在List集合里面带来 --><%List list = new ArrayList();list.add(new Person("aaa"));list.add(new Person("bbb"));list.add(new Person("ccc"));request.setAttribute("list",list); %> ${list[1].name }  <br/><!-- 数据存在Map集合里面带来 --><%Map map = new HashMap();map.put("aa",new Person("aaaaa"));map.put("bb",new Person("bbbbb"));map.put("cc",new Person("ccccc"));map.put("dd",new Person("ddddd"));map.put("111",new Person("eeeee"));request.setAttribute("map",map); %> ${map.bb.name } ${map['111'].name }<%--用el表达式在取数据时，通常用.号，.号取不出来时，用[]--%>   <%-- 取得当前web应用的名称: /day09 ,用于web链接不写死--%> ${pageContext.request.contextPath } <a href="${pageContext.request.contextPath }/index.jsp">点点</a>   </body></html>

JSP代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core"  prefix="c"%><%@ page import="cn.itcast.domain.Person"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>使用jstl+el完成集合迭代</title>  </head>    <body><%List list = new ArrayList();list.add(new Person("aaa"));list.add(new Person("bbb"));list.add(new Person("ccc"));request.setAttribute("list",list); %>        <c:forEach var="person" items="${list}">        ${person.name }<br/>    </c:forEach>            <br/>    <%Map map = new HashMap();map.put("aa",new Person("aaaaa"));map.put("bb",new Person("bbbbb"));map.put("cc",new Person("ccccc"));map.put("dd",new Person("ddddd"));map.put("111",new Person("eeeee"));request.setAttribute("map",map); %>  <c:forEach var="entry" items="${map}"> ${entry.key } : ${entry.value.name}<br/> </c:forEach>  //代表用户登录了 <c:if test="${user!=null}"> 欢迎您：${user.username } </c:if>  //代表用户没登录 <c:if test="${user==null"> 用户名：<input type="text" name="username"/> 密码：<input type="password" name="password"/> </c:if>   </body></html>