一.EL表达式
1.EL是JSP内置的表达式语言
2.从JSP2.0开始，不让再使用java脚本，用EL和动态标签来代替java脚本
3.EL替代的是java脚本的<%= .... %>，没错只能用于输出
4.最常用的是：
（1）全域查找；比如：request.setAttribute("xxx","XXX")，而通过 ${ xxx }就可以查找到XXX
（2）指定域查找；比如：${ requestScope.xxx },在request域中查找
5.JavaBean导航，上代码：
package cn.itcase.domain;
//员工类 public class Employee { private String name; private String age; private Address addr; public Employee() { super(); // TODO Auto-generated constructor stub } public Employee(String name, String age, Address addr) { super(); this.name = name; this.age = age; this.addr = addr; } @Override public String toString() { return "Employee [name=" + name + ", age=" + age + ", addr=" + addr + "]"; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAge() { return age; } public void setAge(String age) { this.age = age; } public Address getAddr() { return addr; } public void setAddr(Address addr) { this.addr = addr; } }
package cn.itcase.domain;
//地址类 public class Address { private String country; private String city; public Address() { super(); // TODO Auto-generated constructor stub } public Address(String country, String city) { super(); this.country = country; this.city = city; } public String getCountry() { return country; } public void setCountry(String country) { this.country = country; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } }
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" import="cn.itcase.domain.*"%> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> <% //设置城市 Address addr = new Address(); addr.setCity("广州"); addr.setCountry("中国"); //设置员工 Employee emp = new Employee(); emp.setName("张三"); emp.setAge("14"); emp.setAddr(addr); //保存到request域中 request.setAttribute("emp", emp); %> //最终得到city的值 ${ requestScope.emp.addr.city } </body> </html>