JSP EL学习笔记

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原文地址：http://www.java3z.com/cwbwebhome/article/article8/8124.html?id=2453

一、JSP EL的运算符

类型

定义

算术型

+ - * / div % mod

逻辑型

and && or || not !

关系型

== eq != ne > gt < lt >= ge <= le

条件型

a?b:c

空

empty

二、JSP EL的基本用法

类型

实例

基本调用方法

JavaBeans

${user.username}

${user["username"]}

${user['username']}

user.getUsername()

数组

${sport[1]}

${sport["1"]}

${sport['1']}

sport[1]

List

${phone[2]}

${phone["2"]}

${phone['2']}

phone.get(2)

Map

${phone.home}

${phone["home"]}

${phone['home']}

phone.get("home")

三、JSP EL的内容对象

pageContext  当前页面上下文件对象
pageScope  page对象
requestScope  request对象
sessionScope  session对象
applicationScope  application对象
param  得到页面传来的参数
paramValues  得到页面传来的多个参数，返回一个数组
header  获取头信息
headerValues  获取头信息的值
cookie  获取cookie对象的值
initParam  获取设定初始的参数值

例：

<%=session.getAttribute("phone")%>

等价于${sessionScope.phone}

四、如何设置JSP不使用JSP EL

1、当前页面不要用JSP EL

<%@page isELIgnored="true" %>

2、整个web应用都不使用EL，修改web.xml文件

<web-app...>

 <jsp-config>

 <jsp-property-group>

 <url-pattern>*.jsp</url-pattern>

 <el-ignored>true</el-ignored>

 </jsp-property-group>

 </jsp-config>

</web-app...>

五、实例

1、基本运算符的实例

<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <title>My JSP 'elExample1.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">
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="This is my page">
 
 </head>
 <body>
 
 ${10+10 } 
 ${10-10 } 
 ${10*10 } 
 ${10/10 } 
 ${10 div 10 } 
 ${10%10 } 
 ${10 mod 10 } 
 
 \${10+10 } 
 '$'{10+10 } 

 
 ${100>200 } 
 ${100 gt 200 } 
 ${100<200 } 
 ${100 lt 200 } 
 ${100>=200 } 
 ${100 ge 200 } 
 ${100<=200 } 
 ${100 le 200 } 
 ${100==200 } 
 ${100 eq 200 } 
 ${100 !=200 } 
 ${100 ne 200 } 
 
 ${'e' eq 'h' } 
 ${"hit" > "him" } 

 
 ${(10>2) && (34>25) } 
 ${(10>2) and (34>25) } 
 ${(10>2) || (34>25) } 
 ${(10>2) or (34>25) } 
 ${!(10>2)} 
 ${not(10>2)} 

 
 <%
 pageContext.setAttribute("username",null);
 pageContext.setAttribute("password","");
 pageContext.setAttribute("city","北京");
 pageContext.setAttribute("date",new java.util.Date());
 %>
 
 ${empty username } 
 
 ${empty password } 
 
 ${empty city } 
 
 ${empty date } 

 </body>
</html>

2、用JSP EL读取JavaBean中的值

<%@ page language="java" pageEncoding="UTF-8"%>
<%@ page import="java.util.*,com.meixin.beans.*"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <title>My JSP 'elExample1.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">
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="This is my page">
 
 </head>
 <body>
 
 <jsp:useBean id="user" class="com.meixin.beans.User"></jsp:useBean>
 <jsp:setProperty name="user" property="username" value="meixin"/>
 <%
 //建立Profile对象，设置邮件地址
 Profile p = new Profile();
 p.setEmail("wnight88@sina.com");

 //将不同的电话存入Map中，并设置在p对象的属性中
 Map<String,String> phone = new HashMap<String,String>();
 phone.put("office","8383838");
 p.setPhone(phone);

 //建立地址对象，设置城市名
 Address address = new Address();
 address.setCity("北京");
 Address[] addresses = {address};
 p.setAddress(addresses);
 user.setProfile(p);
 %>
 
 
 ${user.username } 
 ${user["username"] } 
 ${user['username'] } 
 
 ${user.profile.phone.office } 
 ${user['rofile']['phone']['office'] } 
 
 ${user.profile.address[0].city } 
 </body>
</html>

以下为对象的JavaBean的内容

1)Profile类

package com.meixin.beans;
import java.util.Date;
import java.util.Map;
public class Profile
{
 private String email;
 private Date birthday;
 private Address[] address;
 private Map<String, String> phone;
 public String getEmail()
 {
 return email;
 }
 public void setEmail(String email)
 {
 this.email = email;
 }
 public Date getBirthday()
 {
 return birthday;
 }
 public void setBirthday(Date birthday)
 {
 this.birthday = birthday;
 }
 public Address[] getAddress()
 {
 return address;
 }
 public void setAddress(Address[] address)
 {
 this.address = address;
 }
 public Map<String, String> getPhone()
 {
 return phone;
 }
 public void setPhone(Map<String, String> phone)
 {
 this.phone = phone;
 }
}

2)User类

package com.meixin.beans;
public class User
{
  private Long userID;
  private String userName;
  private String password;
  private Profile profile;

  public Long getUserID()
  {
    return userID;
  }
  public void setUserID(Long userID)
  {
    this.userID = userID;
  }
  public String getUserName()
  {
    return userName;
  }
  public void setUserName(String userName)
  {
    this.userName = userName;
  }
  public String getPassword()
  {
    return password;
  }
  public void setPassword(String password)
  {
    this.password = password;
  }
  public Profile getProfile()
  {
    return profile;
  }
  public void setProfile(Profile profile)
  {
    this.profile = profile;
  }

}

3)Address类

package com.meixin.beans;
public class Address
{
  private String city;
  public String getCity()
  {
    return city;
  }
  public void setCity(String city)
  {
    this.city = city;
  }
}

3、实例：输出页面不同范围内属性的值

4、实例：param用于获取上一页面传递的参数值

${param.username} 
${param.password}

5、实例：cookie用于获取cookie参数的值

<%
response.addCookie(new Cookie("username","meixin"));
%>

${cookie.user.value }

6、实例：initParam用于获取web.xml中初始的参数值

1)web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
 xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 
 <context-param>
 <param-name>repeat</param-name>
 <param-value>100</param-value>
 </context-param>
 <welcome-file-list>
 <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>
</web-app>

2)JSP EL代码

${initParam.repeat}

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