实例解析JSP中EL表达式的各种运用-侯体宗的博客

实例解析JSP中EL表达式的各种运用
Java / 管理员发布于 7年前 143

EL运算符：

<%@page language="java" contentType="text/html;charset=gb2312"%><%@page import="java.sql.*" %><!DOCTYPE html><html>  <head>    <title>El算数运算符</title>  </head>  <body>    <table border=1>      <tr>        <td>算数运算符</td>        <td>结果</td>      </tr>      <tr>        <td>加法运算符\${1 + 1}</td>        <td>结果${1+1}</td>      </tr>      <tr>        <td>减法运算符\${1 - 1}</td>        <td>结果${1-1}</td>      </tr>      <tr>        <td>乘法运算符\${1 * 2}</td>        <td>结果${1 * 1}</td>      </tr>      <tr>        <td>除法运算符\${3 / 2}</td>        <td>结果${3 / 2}</td>      </tr>      <tr>        <td>求余运算符\${3 % 2}</td>        <td>结果${3 % 2}</td>      </tr>    </table>    <table border=1>      <tr>        <td>关系运算符</td>        <td>结果</td>      </tr>      <tr>        <td>等于运算符\${1 == 1}</td>        <td>结果${1==1}</td>      </tr>      <tr>        <td>不等于运算符\${1 != 1}</td>        <td>结果${1!=1}</td>      </tr>      <tr>        <td>小于运算符\${1 < 2}</td>        <td>结果${1 < 2}</td>      </tr>      <tr>        <td>大于运算符\${3 > 2}</td>        <td>结果${3 > 2}</td>      </tr>      <tr>        <td>小于等于运算符\${1 <= 2}</td>        <td>结果${1 <= 2}</td>      </tr>      <tr>        <td>大于等于运算符\${3 >= 2}</td>        <td>结果${3 >= 2}</td>      </tr>    </table>    <table border=1>      <tr>        <td>逻辑运算符</td>        <td>结果</td>      </tr>      <tr>        <td colspan="2">逻辑运算符&&</td>      </tr>      <tr>        <td>\${true && true}</td>        <td>结果${true && true}</td>      </tr>      <tr>        <td>\${true && false}</td>        <td>结果${true && false}</td>      </tr>      <tr>        <td>\${false && false}</td>        <td>结果${false && false}</td>      </tr>      <tr>        <td colspan="2">逻辑运算符||</td>      </tr>      <tr>        <td>\${true || true}</td>        <td>结果${true || true}</td>      </tr><tr>        <td>\${true || false}</td>        <td>结果${true || false}</td>      </tr><tr>        <td>\${false || false}</td>        <td>结果${false || false}</td>      </tr>      <tr>        <td colspan="2">逻辑运算符!</td>      </tr>      <tr>        <td>\${!true}</td>        <td>结果${!true}</td>      </tr><tr>        <td>\${!false}</td>        <td>结果${!false}</td>      </tr>    </table>    <table border=1>      <tr>        <td>条件运算符</td>        <td>结果</td>      </tr>      <tr>        <td>\${2>1?"Yes":"No"}</td>        <td>结果${2>1?"Yes":"No"}</td>      </tr>      <tr>        <td>\${2<1?"Yes":"No"}</td>        <td>结果${2<1?"Yes":"No"}</td>      </tr>    </table>    <table border=1>      <tr>        <td>验证运算符</td>        <td>结果</td>      </tr>      <tr>        <td>\${empty param.username}</td>        <td>结果${empty param.username}</td>      </tr>      <tr>        <td>\${empty param.password}</td>        <td>结果${empty param.password}</td>      </tr>    </table>    <table border=1>      <tr>        <td>括号运算符及运算符的优先级</td>        <td>结果</td>      </tr>    </table>  </body></html>

EL处理内置对象：
“.”和"[]"符号是用来存取数据的

${applicationScope.user.username}${applicationScope.user[0].username}${applicationScope.user["user-name"]}

通过变量来传值就必须使用[]

${applicationScope.user["data"]}

与存储有关的内置对象

<!DOCTYPE html><html>  <head>    <title>与存储有关的内置对象</title>  </head>  <body>    <%      //application范围设置属性name，值为application_name      application.setAttribute("name","application_name");      //session范围设置属性name，值为session_name      session.setAttribute("name","session_name");      //request范围设置属性name，值为request_name      request.setAttribute("name","request_name");      //page范围设置属性name，值为page_name      pageContext.setAttribute("name","page_name");    %>    <%--获取page范围内的name属性--%>    page范围内的那么属性的值为：${pageScope.name}<br />    <%--获取request范围内的name的属性--%>    request范围内的那么属性的值为：${requestScope.name}<br />    <%--获取session范围内的name的属性--%>    session范围内的那么属性的值为：${sessionScope.name}<br />    <%--获取application范围内的name属性--%>    application范围内的那么属性的值为：${applicationScope.name}<br />  </body></html>

与输入有关的内置对象

<!DOCTYPE html><html>  <head>    <title>用户表单</title>  </head>  <body>    <form action="UserDemo.jsp" method="post">      用户名：<input type="text" name="username" /><br />      密码：<input type="password" name="password" /><br />      姓名：<input type="text" name="name" /><br />      性别：<input type="radio" name="sex" value="男">男<input type="radio" name="sex" value="女">女<br />      爱好：<br />      <input type="checkbox" name="interest" value="打篮球">打篮球<br />      <input type="checkbox" name="interest" value="看书">看书<br />      <input type="checkbox" name="interest" value="旅行">旅行<br />      <input type="checkbox" name="interest" value="编程">编程<br />      <input type="submit" value="提交">      <input type="reset" value="重置">    </form>  </body></html><!DOCTYPE html><html>  <head>    <title>接收用户参数</title>  </head>  <body>    <%      //设置页面编码格式      request.setCharacterEncoding("gb2312");    %>    <%--接收用户参数--%>    用户名：${<span style="color:#003399;">param</span>.username}<br />    密码：${<span style="color:#003399;">param</span>.password}<br />    姓名：${<span style="color:#003399;">param</span>.name}<br />    性别：${<span style="color:#003399;">param</span>.sex}<br />    爱好：${<span style="color:#003399;">paramValues</span>.interest[0]}        ${<span style="color:#003399;">paramValues</span>.interest[1]}  </body></html>

cookie内置对象

<!DOCTYPE html><html>  <head>    <title>设置cookie的值</title>  </head>  <body>    <%      //设置cookie的值      Cookie c = new Cookie("username","root");      //添加cookie到客户端      response.addCookie(c);    %>    <a href="https:/article/getCookieDemo.jsp">显示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的值为：${cookie.username.value}  </body></html>

header内置对象

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

initParam内置对象:获取web站点中设置的环境变量

<%@page language="java" contentType="text/html;charset=gb2312"%><!DOCTYPE html><html>  <head>    <title>获得环境参数</title>  </head>  <body>    username参数值：${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内置对象
用来取得有关用户请求和页面的详细信息

<%@page language="java" contentType="text/html;charset=gb2312"%><!DOCTYPE html><html>  <head>    <title>pageContext演示</title>  </head>  <body>    <table border="1">      <tr>        <td>取得请求的参数的字符串</td>        <td>${pageContext.request.queryString}</td>      </tr><tr>        <td>取得请求URL</td>        <td>${pageContext.request.requestURL}</td>      </tr><tr>        <td>取得web应用名称</td>        <td>${pageContext.request.contextPath}</td>      </tr><tr>        <td>取得HTTP请求方式（POST/GET）</td>        <td>${pageContext.request.method}</td>      </tr><tr>        <td>取得使用的协议</td>        <td>${pageContext.request.protocol}</td>      </tr><tr>        <td>取得用户IP地址</td>        <td>${pageContext.request.remoteAddr}</td>      </tr><tr>        <td>判断session是否为新</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:
使用存取器读取JavaBean中的数据

package com.javaweb.ch08;import java.util.*;//一个简单的JavaBean示例public class Person{  //name属性  private String name;  //age属性  private int age;  //sex属性  private String sex;  //friends属性  private ArrayList friends;  //无参构造方法  public Person(){  }  //自定义构造的方法  public Person(String name,int age,String sex){    this.name = name;    this.age = age;    this.sex = sex;  }  //获取name的属性值  public String getName(){    return name;  }  //获取age属性值  public int getAge(){    return age;  }  //获取sex的属性值  public String getSex(){    return sex;  }  //设置name的属性  public void setName(String name){    this.name = name;  }  //设置age的属性值  public void setAge(int age){    this.age = age;  }  //设置sex的属性值  public void setSex(String sex){    this.sex = sex;  }  //设置friends的值  public void setFriends(ArrayList friends){    this.friends = friends;  }  //获取friends的属性值  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>设置JavaBean中的属性</title>  </head>  <body>    <%    //实例化一个Person    Person person = new Person("zhangdapeng",24,"男");    //创建一个friends实例    ArrayList friends = new ArrayList();    //添加值    friends.add("wang wu");    friends.add("li si");    person.setFriends(friends);    //存储在session范围内    session.setAttribute("person",person);         %>    <a href="https:/article/GetJavaBean.jsp">跳转到GetJavaBean.jsp</a>  </body></html><%@page language="java" contentType="text/html;charset=gb2312"%><!DOCTYPE html><html>  <head>    <title>取得JavaBean中的属性值</title>  </head>  <body>    姓名：${sessionScope.person.name}<br />    年龄：${sessionScope.person.age}<br />    性别：${sessionScope.person.sex}<br />    朋友：${sessionScope.person.friends[0]},${sessionScope.person.friends[1]}<br />  </body></html>

使用存储器读取Map中的数据

<%@page language="java" contentType="text/html;charset=gb2312"%><%@page import="java.util.*,com.javaweb.ch08.*" %><!DOCTYPE html><html>  <head>    <title>设置Map页面</title>  </head>  <body>    <%      //新建一个HashMap      HashMap userInfo = new HashMap();      //在HashMap中设置值      userInfo.put("username","zhangdapeng");      userInfo.put("password","zhnagda123");      //将值存储到session范围中      session.setAttribute("userInfo",userInfo);           %>    <a href="https:/article/GetMapDemo.jsp">跳转到GetMapDemo.jsp</a>  </body></html><%@page language="java" contentType="text/html;charset=gb2312"%><!DOCTYPE html><html>  <head>    <title>使用存储器读取map中的数据</title>  </head>  <body>    用户名：${sessionScope.userInfo.username}<br />    密码：${sessionScope.userInfo.password}<br />  </body></html>

使用存储器读取数组中的数据

<%@page language="java" contentType="text/html;charset=gb2312"%><%@page import="java.util.*,com.javaweb.ch08.*" %><!DOCTYPE html><html>  <head>    <title>设置Array页面</title>  </head>  <body>    <%      String[] names = {"zhangda1","zhangda2","zhangda3"};      //将值存储到session范围中      session.setAttribute("names",names);           %>    <a href="https:/article/GetMapDemo.jsp">跳转到GetArrayDemo.jsp</a>  </body></html><%@page language="java" contentType="text/html;charset=gb2312"%><!DOCTYPE html><html>  <head>    <title>使用存储器读取map中的数据</title>  </head>  <body>    用户名1：${sessionScope.names[0]}<br />    用户名2：${sessionScope.names[1]}<br />  </body></html>

存储器的复杂应用

<%@page language="java" contentType="text/html;charset=gb2312"%><%@page import="java.util.*,com.javaweb.ch08.*" %><!DOCTYPE html><html>  <head>    <title>设置Array页面</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="https:/article/GetMapDemo.jsp">跳转到GetArrayDemo.jsp</a>  </body></html><%@page language="java" contentType="text/html;charset=gb2312"%><!DOCTYPE html><html>  <head>    <title>使用存储器读取map中的数据</title>  </head>  <body>    用户名1：${sessionScope.persons[0].name},${sessionScope.persons[0].age},${sessionScope.persons[0].sex}<br />    用户名2：${sessionScope.persons[1].name},${sessionScope.persons[1].age},${sessionScope.persons[1].sex}<br />  </body></html>

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