EL表达式和JSTL标签的用法举例

来源：互联网发布：淘宝客软件编辑：程序博客网时间：2024/05/19 03:42

Person类

package cn.itcast.domain;import java.util.Date;public class Person {private String name;private Address address;public Person() {}public Person(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Address getAddress() {return address;}public void setAddress(Address address) {this.address = address;}}

Address类：

package cn.itcast.domain;public class Address {private String city;public String getCity() {return city;}public void setCity(String city) {this.city = city;}}

Servlet要么通过域带过来，对象带过来，集合带过来，所以，EL表达式取出元素的几种方式：

<%@page import="java.util.*"%><%@page import="cn.itcast.domain.*"%><%@ page language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Insert title here</title></head><body><%String data = "abcd";request.setAttribute("data", data);%>${data }<%--pageContext.findAttribute("data") page request session application --%><br /><%Person p = new Person();p.setName("aaaa");request.setAttribute("person", p);%>${person.name }<%--pageContext.findAttribute("person") page request session application --%><br /><%Person p1 = new Person();Address a = new Address();a.setCity("成都");p1.setAddress(a);request.setAttribute("p1", p1);%>${p1.address.city }<br /><%List<Person> list = new ArrayList<Person>();list.add(new Person("aaa"));list.add(new Person("bbb"));list.add(new Person("ccc"));request.setAttribute("list", list);%>${list[1].name }<br /><%Map<String, Person> map = new HashMap<String, Person>();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("11", new Person("eeeee"));//一般不以数字作为关键字，若要这么做那么EL表达式的写法为${map['11'].name}request.setAttribute("map", map);%><!-- 以关键字去找集合的元素 -->${map }<!-- 找到集合 --><br /> ${map.aa }<!-- 用关键字找到对象 --><br /> ${map.bb.name }<!-- 找到对象的name --><br /> ${map['11'].name }<!-- 用EL表达式取数据一般是用.号，.号取不出数据时用[] --><!-- Servlet要么通过域带过来，对象带过来，集合带过来 --><br />${pageContext.request.contextPath }<!-- 获取当前Web应用的名称 --><br /><a href="/Web/index.jsp" />点击</a><!-- 一般不能这样写 --><a href="${pageContext.request.contextPath }/index.jsp">点击</a></body></html>

JSTL标签遍历集合列表：

<%@page import="java.util.*"%><%@page import="cn.itcast.domain.Person"%><%@taglib uri="http://java.sun.com/jsp/jstl/core"  prefix="c"%><%@ page language="java" contentType="text/html; charset=utf-8"    pageEncoding="utf-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>JSTL标签遍历集合列表</title></head><body><%List<Person> list = new ArrayList<Person>();list.add(new Person("aaa"));list.add(new Person("bbb"));list.add(new Person("ccc"));request.setAttribute("list", list);//保存到request域中%><br /><c:forEach var="person" items="${list }">${person.name }<br /></c:forEach><%Map<String, Person> map = new HashMap<String, Person>();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("11", new Person("eeeee"));//一般不以数字作为关键字，若要这么做那么EL表达式的写法为${map['11'].name}request.setAttribute("map", map);%><c:forEach var="entry" items="${map }">${entry.key }:${entry.value.name }<br /></c:forEach><!-- 代表用户登录 --><c:if test="${user!=null }">欢迎您:${user.username }</c:if><c:if test="${user==null }">用户名:<input type="text" name="username"><br />密   码:<input type="password" name="password"><br /><input type="submit" value="登录" /></c:if></body></html>

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