EL表达式（二）运算符

运算符"."和"[]": "."能做的"[]"也能做，"[]"能做的"."不一定能做。java不识别的用"[]"

算数运算符：+,-,*,/或div,%或mod
关系运算符：==或eq,!=或ne,<或lt,>或gt,<=或le,>=或ge
逻辑运算符： &&或and , ||或or , !或not
其他运算符： empty 当判断的对象为null或空字符串否返回true，集合对象部位null，但无元素是返回true , ?: 三元运算符(${a?b:c})

EL表达式不支持字符串链接

1. Java

 package cn.gs.ly.mvc.domain;

 import java.util.Date;

 public class Person {

     private String name;

     private String gender;

     private boolean married;

     private Date birthday;

     private Address address = new Address();

     public Person() {

     }

     public Person(String name, String gender, boolean married) {

         super();

         this.name = name;

         this.gender = gender;

         this.married = married;

     }

     public Address getAddress() {

         return address;

     }

     public void setAddres(Address address) {

         this.address = address;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getGender() {

         return gender;

     }

     public void setGender(String gender) {

         this.gender = gender;

     }

     public boolean isMarried() {

         return married;

     }

     public void setMarried(boolean married) {

         this.married = married;

     }

     public Date getBirthday() {

         return birthday;

     }

     public void setBirthday(Date birthday) {

         this.birthday = birthday;

     }

 }

2. jsp

 <%@page import="java.util.HashMap"%>

 <%@page import="java.util.Map"%>

 <%@page import="java.util.ArrayList"%>

 <%@page import="java.util.List"%>

 <%@page import="cn.gs.ly.mvc.domain.Person"%>

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>

 <!DOCTYPE html>

 <html>

 <head>

 <title>Insert title here</title>

 </head>

 <body>

     <%

         pageContext.setAttribute("num1", "100");

         pageContext.setAttribute("num2", "20");

     %>

     加法:${num1+num2 }<hr/>

     减法:${num1-num2 }<hr/>

     乘法:${num1*num2 }<hr/>

     除法:${num1/num2 }或${num1 div num2 }<hr/>

     取模:${num1%num2 }或${num1 mod num2 }<hr/>

     等于:${num1==num2 }或${num1 eq num2 }<hr/>

     不等于:${num1!=num2 }或${num1 ne num2 }<hr/>

     大于:${num1>num2 }或${num1 gt num2 }<hr/>

     小于:${num1<num2 }或${num1 lt num2 }<hr/>

     大于等于:${num1>=num2 }或${num1 ge num2 }<hr/>

     小于等于:${num1<=num2 }或${num1 le num2 }<hr/>

     实例化前:${empty p}<hr/>

     实例化前:${empty ""}<hr/>

     <jsp:useBean id="p" class="cn.gs.ly.mvc.domain.Person"></jsp:useBean>

     实例化后:${empty p}<hr/>

     实例化后:${empty ""}<hr/>

     实例化后:${empty " "}<hr/>

     <%

         List list = new ArrayList();

         list.add("a");

         pageContext.setAttribute("list", list);

         session.setAttribute("user", "liuchao");

         pageContext.setAttribute("gender", "0");// 0男1女

     %>

     list集合:${empty list }<hr/>

     user:${empty sessionScope.user?"请登录":"欢迎" }${user }<hr/>

     性别:${gender==0?"男":"女" }<hr/>

 </body>

 </html>

3. 运行结果

巴特西

EL表达式（二）运算符

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