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實(shí)例解析JSP中EL表達(dá)式的各種運(yùn)用

 更新時(shí)間：2016年04月14日 14:35:29   作者：張大鵬  
這篇文章主要介紹了JSP中EL表達(dá)式的各種運(yùn)用,比如用EL處理數(shù)學(xué)運(yùn)算、內(nèi)置對(duì)象以及數(shù)據(jù)的存取等,代碼示例都相當(dāng)實(shí)用,需要的朋友可以參考下

EL運(yùn)算符：

<%@page language="java" contentType="text/html;charset=gb2312"%>
<%@page import="java.sql.*" %>
<!DOCTYPE html>
<html>
  <head>
    <title>El算數(shù)運(yùn)算符</title>
  </head>
  <body>
    <table border=1>
      <tr>
        <td>算數(shù)運(yùn)算符</td>
        <td>結(jié)果</td>
      </tr>
      <tr>
        <td>加法運(yùn)算符\${1 + 1}</td>
        <td>結(jié)果${1+1}</td>
      </tr>
      <tr>
        <td>減法運(yùn)算符\${1 - 1}</td>
        <td>結(jié)果${1-1}</td>
      </tr>
      <tr>
        <td>乘法運(yùn)算符\${1 * 2}</td>
        <td>結(jié)果${1 * 1}</td>
      </tr>
      <tr>
        <td>除法運(yùn)算符\${3 / 2}</td>
        <td>結(jié)果${3 / 2}</td>
      </tr>
      <tr>
        <td>求余運(yùn)算符\${3 % 2}</td>
        <td>結(jié)果${3 % 2}</td>
      </tr>
    </table>
    <table border=1>
      <tr>
        <td>關(guān)系運(yùn)算符</td>
        <td>結(jié)果</td>
      </tr>
      <tr>
        <td>等于運(yùn)算符\${1 == 1}</td>
        <td>結(jié)果${1==1}</td>
      </tr>
      <tr>
        <td>不等于運(yùn)算符\${1 != 1}</td>
        <td>結(jié)果${1!=1}</td>
      </tr>
      <tr>
        <td>小于運(yùn)算符\${1 &lt; 2}</td>
        <td>結(jié)果${1 < 2}</td>
      </tr>
      <tr>
        <td>大于運(yùn)算符\${3 &gt; 2}</td>
        <td>結(jié)果${3 > 2}</td>
      </tr>
      <tr>
        <td>小于等于運(yùn)算符\${1 &lt;= 2}</td>
        <td>結(jié)果${1 <= 2}</td>
      </tr>
      <tr>
        <td>大于等于運(yùn)算符\${3 &gt;= 2}</td>
        <td>結(jié)果${3 >= 2}</td>
      </tr>
    </table>
    <table border=1>
      <tr>
        <td>邏輯運(yùn)算符</td>
        <td>結(jié)果</td>
      </tr>
      <tr>
        <td colspan="2">邏輯運(yùn)算符&&</td>
      </tr>
      <tr>
        <td>\${true && true}</td>
        <td>結(jié)果${true && true}</td>
      </tr>
      <tr>
        <td>\${true && false}</td>
        <td>結(jié)果${true && false}</td>
      </tr>
      <tr>
        <td>\${false && false}</td>
        <td>結(jié)果${false && false}</td>
      </tr>
      <tr>
        <td colspan="2">邏輯運(yùn)算符||</td>
      </tr>
      <tr>
        <td>\${true || true}</td>
        <td>結(jié)果${true || true}</td>
      </tr><tr>
        <td>\${true || false}</td>
        <td>結(jié)果${true || false}</td>
      </tr><tr>
        <td>\${false || false}</td>
        <td>結(jié)果${false || false}</td>
      </tr>
      <tr>
        <td colspan="2">邏輯運(yùn)算符!</td>
      </tr>
      <tr>
        <td>\${!true}</td>
        <td>結(jié)果${!true}</td>
      </tr><tr>
        <td>\${!false}</td>
        <td>結(jié)果${!false}</td>
      </tr>
    </table>
    <table border=1>
      <tr>
        <td>條件運(yùn)算符</td>
        <td>結(jié)果</td>
      </tr>
      <tr>
        <td>\${2>1?"Yes":"No"}</td>
        <td>結(jié)果${2>1?"Yes":"No"}</td>
      </tr>
      <tr>
        <td>\${2<1?"Yes":"No"}</td>
        <td>結(jié)果${2<1?"Yes":"No"}</td>
      </tr>
    </table>
    <table border=1>
      <tr>
        <td>驗(yàn)證運(yùn)算符</td>
        <td>結(jié)果</td>
      </tr>
      <tr>
        <td>\${empty param.username}</td>
        <td>結(jié)果${empty param.username}</td>
      </tr>
      <tr>
        <td>\${empty param.password}</td>
        <td>結(jié)果${empty param.password}</td>
      </tr>
    </table>
    <table border=1>
      <tr>
        <td>括號(hào)運(yùn)算符及運(yùn)算符的優(yōu)先級(jí)</td>
        <td>結(jié)果</td>
      </tr>
    </table>
  </body>
</html>

EL處理內(nèi)置對(duì)象：
“.”和"[]"符號(hào)是用來(lái)存取數(shù)據(jù)的

${applicationScope.user.username}

${applicationScope.user[0].username}

${applicationScope.user["user-name"]}

通過(guò)變量來(lái)傳值就必須使用[]

${applicationScope.user["data"]}

與存儲(chǔ)有關(guān)的內(nèi)置對(duì)象

<!DOCTYPE html>
<html>
  <head>
    <title>與存儲(chǔ)有關(guān)的內(nèi)置對(duì)象</title>
  </head>
  <body>
    <%
      //application范圍設(shè)置屬性name，值為application_name
      application.setAttribute("name","application_name");
      //session范圍設(shè)置屬性name，值為session_name
      session.setAttribute("name","session_name");
      //request范圍設(shè)置屬性name，值為request_name
      request.setAttribute("name","request_name");
      //page范圍設(shè)置屬性name，值為page_name
      pageContext.setAttribute("name","page_name");
    %>
    <%--獲取page范圍內(nèi)的name屬性--%>
    page范圍內(nèi)的那么屬性的值為：${pageScope.name}<br />
    <%--獲取request范圍內(nèi)的name的屬性--%>
    request范圍內(nèi)的那么屬性的值為：${requestScope.name}<br />
    <%--獲取session范圍內(nèi)的name的屬性--%>
    session范圍內(nèi)的那么屬性的值為：${sessionScope.name}<br />
    <%--獲取application范圍內(nèi)的name屬性--%>
    application范圍內(nèi)的那么屬性的值為：${applicationScope.name}<br />
  </body>
</html>

與輸入有關(guān)的內(nèi)置對(duì)象

<!DOCTYPE html>
<html>
  <head>
    <title>用戶表單</title>
  </head>
  <body>
    <form action="UserDemo.jsp" method="post">
      用戶名：<input type="text" name="username" /><br />
      密碼：<input type="password" name="password" /><br />
      姓名：<input type="text" name="name" /><br />
      性別：<input type="radio" name="sex" value="男">男<input type="radio" name="sex" value="女">女<br />
      愛(ài)好：<br />
      <input type="checkbox" name="interest" value="打籃球">打籃球<br />
      <input type="checkbox" name="interest" value="看書(shū)">看書(shū)<br />
      <input type="checkbox" name="interest" value="旅行">旅行<br />
      <input type="checkbox" name="interest" value="編程">編程<br />
      <input type="submit" value="提交">
      <input type="reset" value="重置">
    </form>
  </body>
</html>


<!DOCTYPE html>
<html>
  <head>
    <title>接收用戶參數(shù)</title>
  </head>
  <body>
    <%
      //設(shè)置頁(yè)面編碼格式
      request.setCharacterEncoding("gb2312");
    %>
    <%--接收用戶參數(shù)--%>
    用戶名：${<span style="color:#003399;">param</span>.username}<br />
    密碼：${<span style="color:#003399;">param</span>.password}<br />
    姓名：${<span style="color:#003399;">param</span>.name}<br />
    性別：${<span style="color:#003399;">param</span>.sex}<br />
    愛(ài)好：${<span style="color:#003399;">paramValues</span>.interest[0]}
        ${<span style="color:#003399;">paramValues</span>.interest[1]}
  </body>
</html>

cookie內(nèi)置對(duì)象

<!DOCTYPE html>
<html>
  <head>
    <title>設(shè)置cookie的值</title>
  </head>
  <body>
    <%
      //設(shè)置cookie的值
      Cookie c = new Cookie("username","root");
      //添加cookie到客戶端
      response.addCookie(c);
    %>
    <a href="getCookieDemo.jsp">顯示cookie的值</a>
  </body>
</html>

<span style="color:#000000;"><%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>取得cookie的值</title>
  </head>
  <body>
    cookie中的username的值為：${cookie.username.value}
  </body>
</html>

header內(nèi)置對(duì)象

<!DOCTYPE html>
<html>
  <head>
    <title>取得header的值</title>
  </head>
  <body>
    ${header["host"]}<br />
    ${header["user-agent"]}<br />
  </body>
</html>

initParam內(nèi)置對(duì)象:獲取web站點(diǎn)中設(shè)置的環(huán)境變量

<%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>獲得環(huán)境參數(shù)</title>
  </head>
  <body>
    username參數(shù)值：${initParam.username}<br />
  </body>
</html>

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app 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"
  version="2.5">
  <context-param>
    <param-name>username</param-name>
    <param-value>Zhangdapeng</param-value>
  </context-param>
</web-app>

pageContex內(nèi)置對(duì)象
用來(lái)取得有關(guān)用戶請(qǐng)求和頁(yè)面的詳細(xì)信息

<%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>pageContext演示</title>
  </head>
  <body>
    <table border="1">
      <tr>
        <td>取得請(qǐng)求的參數(shù)的字符串</td>
        <td>${pageContext.request.queryString}</td>
      </tr><tr>
        <td>取得請(qǐng)求URL</td>
        <td>${pageContext.request.requestURL}</td>
      </tr><tr>
        <td>取得web應(yīng)用名稱</td>
        <td>${pageContext.request.contextPath}</td>
      </tr><tr>
        <td>取得HTTP請(qǐng)求方式（POST/GET）</td>
        <td>${pageContext.request.method}</td>
      </tr><tr>
        <td>取得使用的協(xié)議</td>
        <td>${pageContext.request.protocol}</td>
      </tr><tr>
        <td>取得用戶IP地址</td>
        <td>${pageContext.request.remoteAddr}</td>
      </tr><tr>
        <td>判斷session是否為新</td>
        <td>${pageContext.session.new}</td>
      </tr><tr>
        <td>取得session的id</td>
        <td>${pageContext.session.id}</td>
      </tr>
    </table>
  </body>
</html>

EL存取器:
使用存取器讀取JavaBean中的數(shù)據(jù)

package com.javaweb.ch08;
import java.util.*;
//一個(gè)簡(jiǎn)單的JavaBean示例
public class Person{
  //name屬性
  private String name;
  //age屬性
  private int age;
  //sex屬性
  private String sex;
  //friends屬性
  private ArrayList friends;
  //無(wú)參構(gòu)造方法
  public Person(){
  }
  //自定義構(gòu)造的方法
  public Person(String name,int age,String sex){
    this.name = name;
    this.age = age;
    this.sex = sex;
  }
  //獲取name的屬性值
  public String getName(){
    return name;
  }
  //獲取age屬性值
  public int getAge(){
    return age;
  }
  //獲取sex的屬性值
  public String getSex(){
    return sex;
  }
  //設(shè)置name的屬性
  public void setName(String name){
    this.name = name;
  }
  //設(shè)置age的屬性值
  public void setAge(int age){
    this.age = age;
  }
  //設(shè)置sex的屬性值
  public void setSex(String sex){
    this.sex = sex;
  }
  //設(shè)置friends的值
  public void setFriends(ArrayList friends){
    this.friends = friends;
  }
  //獲取friends的屬性值
  public ArrayList getFriends(){
    return friends;
  }
}


<%@page language="java" contentType="text/html;charset=gb2312"%>
<%@page import="java.util.*,com.javaweb.ch08.*" %>
<!DOCTYPE html>
<html>
  <head>
    <title>設(shè)置JavaBean中的屬性</title>
  </head>
  <body>
    <%
    //實(shí)例化一個(gè)Person
    Person person = new Person("zhangdapeng",24,"男");
    //創(chuàng)建一個(gè)friends實(shí)例
    ArrayList friends = new ArrayList();
    //添加值
    friends.add("wang wu");
    friends.add("li si");
    person.setFriends(friends);
    //存儲(chǔ)在session范圍內(nèi)
    session.setAttribute("person",person);
     
    %>
    <a href="GetJavaBean.jsp">跳轉(zhuǎn)到GetJavaBean.jsp</a>
  </body>
</html>

<%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>取得JavaBean中的屬性值</title>
  </head>
  <body>
    姓名：${sessionScope.person.name}<br />
    年齡：${sessionScope.person.age}<br />
    性別：${sessionScope.person.sex}<br />
    朋友：${sessionScope.person.friends[0]},${sessionScope.person.friends[1]}<br />
  </body>
</html>

使用存儲(chǔ)器讀取Map中的數(shù)據(jù)

<%@page language="java" contentType="text/html;charset=gb2312"%>
<%@page import="java.util.*,com.javaweb.ch08.*" %>
<!DOCTYPE html>
<html>
  <head>
    <title>設(shè)置Map頁(yè)面</title>
  </head>
  <body>
    <%
      //新建一個(gè)HashMap
      HashMap userInfo = new HashMap();
      //在HashMap中設(shè)置值
      userInfo.put("username","zhangdapeng");
      userInfo.put("password","zhnagda123");
      //將值存儲(chǔ)到session范圍中
      session.setAttribute("userInfo",userInfo);
       
    %>
    <a href="GetMapDemo.jsp">跳轉(zhuǎn)到GetMapDemo.jsp</a>
  </body>
</html>

<%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>使用存儲(chǔ)器讀取map中的數(shù)據(jù)</title>
  </head>
  <body>
    用戶名：${sessionScope.userInfo.username}<br />
    密碼：${sessionScope.userInfo.password}<br />
  </body>
</html>

使用存儲(chǔ)器讀取數(shù)組中的數(shù)據(jù)

<%@page language="java" contentType="text/html;charset=gb2312"%>
<%@page import="java.util.*,com.javaweb.ch08.*" %>
<!DOCTYPE html>
<html>
  <head>
    <title>設(shè)置Array頁(yè)面</title>
  </head>
  <body>
    <%
      String[] names = {"zhangda1","zhangda2","zhangda3"};
      //將值存儲(chǔ)到session范圍中
      session.setAttribute("names",names);
       
    %>
    <a href="GetMapDemo.jsp">跳轉(zhuǎn)到GetArrayDemo.jsp</a>
  </body>
</html>

<%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>使用存儲(chǔ)器讀取map中的數(shù)據(jù)</title>
  </head>
  <body>
    用戶名1：${sessionScope.names[0]}<br />
    用戶名2：${sessionScope.names[1]}<br />
  </body>
</html>

存儲(chǔ)器的復(fù)雜應(yīng)用

<%@page language="java" contentType="text/html;charset=gb2312"%>
<%@page import="java.util.*,com.javaweb.ch08.*" %>
<!DOCTYPE html>
<html>
  <head>
    <title>設(shè)置Array頁(yè)面</title>
  </head>
  <body>
    <%
      ArrayList<Person> persons = new ArrayList<Person>();
       
      Person person1 = new Person("wang wu",24,"男");
      Person person2 = new Person("wang liu",24,"女");
       
      persons.add(person1);
      persons.add(person2);
       
      session.setAttribute("persons",persons);
       
    %>
    <a href="GetMapDemo.jsp">跳轉(zhuǎn)到GetArrayDemo.jsp</a>
  </body>
</html>

<%@page language="java" contentType="text/html;charset=gb2312"%>
<!DOCTYPE html>
<html>
  <head>
    <title>使用存儲(chǔ)器讀取map中的數(shù)據(jù)</title>
  </head>
  <body>
    用戶名1：${sessionScope.persons[0].name},${sessionScope.persons[0].age},${sessionScope.persons[0].sex}<br />
    用戶名2：${sessionScope.persons[1].name},${sessionScope.persons[1].age},${sessionScope.persons[1].sex}<br />
  </body>
</html>

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