EL表达式和JSTL标签的用法举例
浏览数：36 /
时间：2015年06月09日
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>
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