标签：创建 users 不同 cookie对象 实现 script 忽略 r.js unit
不是说server端的Session空间丢失了，而是在server端找到打开相应Session空间的钥匙（JSESSIONID）丢失了。这时就须要使用Session的追踪技术。
不会导致session丢失（正常关闭server后，会在server中将session存储起来。再次启动server的时候 会被又一次载入到内存中）
public class SessionDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// session域对象
HttpSession session = request.getSession();
session.setAttribute("username", "小风");
// DD64756D56885AF87E883B887BF77E6C jsessionid=DD64756D56885AF87E883B887BF77E6C
System.out.println(session.getId());
response.sendRedirect("/day12/session2");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}package cn.itcast.session;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class SessionDemo2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 手动传入jsessionid=DD64756D56885AF87E883B887BF77E6C
HttpSession session = request.getSession();
String username = (String) session.getAttribute("username");
response.setContentType("text/html;charset=UTF-8");
response.getWriter().write("<h4>訪问到了..."+username+"</h4>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
设置成false不能直接使用session（假设设置成false 要想获取session 仅仅能使用Java代码 <% HttpSession session2 = request.getSession() %>）
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" isErrorPage="true" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h3>亲，server正在维护。！</h3>
<%=exception.getMessage() %>
</body>
</html><%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h3>亲。您訪问的资源恋爱了，不在服务区！！</h3>
</body>
</html>
500.jsp<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h3>亲。server正在维护，这回是真的维护！！</h3>
</body>
</html>
<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" session="true" buffer="8kb" autoFlush="true"
errorPage="/jsp/error.jsp" isELIgnored="false"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>欢迎</h4>
<%
List list = new ArrayList();
// int a = 10 / 0;
request.setAttribute("username", "小风");
%>
<!-- HTML的文本 -->
${ username }
</body>
</html>
nm=browser" %>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%@ include file="/include/head.jsp" %>
<%@ include file="/include/menu.jsp" %>
<h3>站点的新闻（数据变化）</h3>
<%@ include file="/include/foot.jsp" %>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<h3>站点的LOGO</h3>
<% int a = 100; %>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<h3>站点的超链接</h3>
<%= a %>foot.jsp<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<h3>站点的友情链接</h3>
| 内置对象 | 真实的对象 | 方法 |
| request | HttpServletRequest | setAttribute() getAttribute() |
| response | HttpServletResponse | addCookie() getWriter() |
| session | HttpSession | setAttribute() getAttribute() |
| application | ServletContext | setAttribute() getAttribute() |
| config | ServletConfig | getInitParameter() getInitParameterNames() |
| exception | Throwable(全部的异常父类) | getMessage() |
| page | Object | (当前的Servlet对象 this(HttpServlet)) |
| out | JspWriter | write() print() |
| pageContext | PageContext | setAttribute() getAttribute() |
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<!-- BBBB HELLO AAAA CCCC -->
<%= "HELLO" %>
<% out.print("AAAA"); %>
<% response.getWriter().print("BBBB"); %>
<% out.print("CCCC"); %>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%=request.getParameter("username") %>
<h4>pageContext向其它域中存入值</h4>
<%
pageContext.setAttribute("name", "美美");
// 以下这句等价于上面
pageContext.setAttribute("name", "美美", pageContext.PAGE_SCOPE);
request.setAttribute("name", "小凤");
// 向request域中存入值
pageContext.setAttribute("name", "小凤", pageContext.REQUEST_SCOPE);
// 向session域存入值
pageContext.setAttribute("name", "小苍", pageContext.SESSION_SCOPE);
// 向ServletContext域存入值
pageContext.setAttribute("name", "小班长", pageContext.APPLICATION_SCOPE);
%>
<%= pageContext.getAttribute("name", pageContext.SESSION_SCOPE)%>
<%= session.getAttribute("name") %>
${ pageScope.name }
${ requestScope.name }
${ sessionScope.name }
${ applicationScope.name }
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
int a = 10;
%>
<%= a %>
<h3>站点的LOGO</h3>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<h3>站点的超链接</h3>
foot.jsp<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<h3>站点的友情链接</h3>body.jsp<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <jsp:include page="/action/head.jsp"></jsp:include> <jsp:include page="/action/menu.jsp"></jsp:include> <h3>站点的新闻（数据变化）</h3> <jsp:include page="/action/foot.jsp"></jsp:include> </body> </html>执行结果例如以下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>JSP的动作标签</h4>
<jsp:forward page="/jsp/pageContext.jsp">
<jsp:param name="username" value="meimei"/>
</jsp:forward>
</body>
</html>执行结果：
public void populate(Map<String, String[]> map, User user) throws Exception {
BeanInfo info = Introspector.getBeanInfo(user.getClass());
PropertyDescriptor [] pds = info.getPropertyDescriptors();
for (PropertyDescriptor pd : pds) {
String attrName = pd.getName();
if(map.containsKey(attrName)){
Method m = pd.getWriteMethod();
m.invoke(user, map.get(attrName)[0]);
}
}
}
在src下新建cn.itcast.test包，在包内新建InstrospectorTest.java測试类package cn.itcast.test;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import org.junit.Test;
import cn.itcast.vo.User;
/**
* 測试类
* @author Administrator
*
*/
public class IntrospectorTest {
@Test
public void run() throws Exception{
User user = new User();
// 获取类的信息
BeanInfo info = Introspector.getBeanInfo(user.getClass());
// 获取属性的描写叙述
PropertyDescriptor [] pds = info.getPropertyDescriptors();
// 循环遍历，获取属性的名称
for (PropertyDescriptor pd : pds) {
// System.out.println(pd.getName());
if(!"class".equals(pd.getName())){
// 获取写的方法
Method m = pd.getWriteMethod();
m.invoke(user, "admin");
}
}
System.out.println(user.getUsername());
System.out.println(user.getPassword());
}
}
重写该方法。把字符串转换日期。
public class MyConvert implements Converter{
/**
* 实现转换的方法
* clazz：类型
* obj：输入的内容
*/
public Object convert(Class clazz, Object obj) {
String sDate = (String)obj;
// 把字符串转换成日期
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date;
try {
date = sdf.parse(sDate);
} catch (ParseException e) {
e.printStackTrace();
throw new RuntimeException("日期转换错误");
}
return date;
}
}
// 进行日期转换注冊
ConvertUtils.register(new MyConvert(), Date.class);
程序实比例如以下：package cn.itcast.vo;
import java.util.Date;
/**
* User的JavaBean
* @author Administrator
*
*/
public class User {
private String username;
private String password;
private double money;
private Date birthday;
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 double getMoney() {
return money;
}
public void setMoney(double money) {
this.money = money;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
}
在src下新建cn.itcast.utils包（工具类） 在里面新建MyDateConverter.java 类（用于注冊其它类型的Bean）package cn.itcast.utils;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import org.apache.commons.beanutils.Converter;
/**
* 字符串转换日期类
* @author Administrator
*
*/
public class MyDateConverter implements Converter{
/**
* 字符串转换成日期
*/
public Object convert(Class clazz, Object obj) {
// 把输入的字符串，转换成日期类型。返回
String dDate = (String) obj;
// 把字符串转换成日期
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date;
try {
date = sdf.parse(dDate);
} catch (ParseException e) {
e.printStackTrace();
throw new RuntimeException("转换日期错误");
}
return date;
}
}
在src下新建cn.itcast.servlet包，在包内新建UserServlet.java类（实现内省）和UserBeanUtilServlet.java（实现日期属性为Bean赋值）package cn.itcast.servlet;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.itcast.vo.User;
/**
* 获取请求參数，封装数据
* @author Administrator
*
*/
public class UserServlet extends HttpServlet {
private static final long serialVersionUID = 6390620317553505800L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 获取请求參数，创建User对象，设置值。
/**
*
* // 获取表单的内容
String username = request.getParameter("username");
String password = request.getParameter("password");
// 创建User对象，set设置值
User user = new User();
user.setUsername(username);
user.setPassword(password);
*/
// 获取输入的数据
Map<String, String []> map = request.getParameterMap();
// 创建User对象
User user = new User();
// 自己编写封装数据的方法
try {
populate(map,user);
} catch (Exception e) {
e.printStackTrace();
}
// 完毕数据封装
System.out.println(user.getUsername());
System.out.println(user.getPassword());
}
/**
* 完毕的数据
* @param map
* @param user
* @throws Exception
*/
private void populate(Map<String, String[]> map, User user) throws Exception {
BeanInfo info = Introspector.getBeanInfo(user.getClass());
// 获取属性的描写叙述
PropertyDescriptor [] pds = info.getPropertyDescriptors();
// 循环遍历
for (PropertyDescriptor pd : pds) {
// 获取到属性的名称
String name = pd.getName();
// map的key
if(map.containsKey(name)){
// 获取属性的写的方法
Method m = pd.getWriteMethod();
// 运行之
m.invoke(user, map.get(name)[0]);
}
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}UserBeanUtilServlet.java /userBeanUtilpackage cn.itcast.servlet;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Date;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.beanutils.ConvertUtils;
import cn.itcast.utils.MyDateConverter;
import cn.itcast.vo.User;
/**
* 使用BeanUtils完毕数据的封装
* @author Administrator
*
*/
public class UserBeanUtilServlet extends HttpServlet {
private static final long serialVersionUID = 3625882115495534032L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 获取数据
Map<String, String []> map = request.getParameterMap();
// 创建User对象
User user = new User();
// 完毕注冊
ConvertUtils.register(new MyDateConverter(), Date.class);
// 完毕封装
try {
BeanUtils.populate(user, map);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
// 打印
System.out.println(user.getUsername());
System.out.println(user.getPassword());
System.out.println(user.getMoney());
System.out.println(user.getBirthday());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
在WebRoot下新建目录bean目录，在目录下新建login.jsp 和success.jsp文件<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>表单提交到JSP的页面</h4>
<form action="/day12/bean/success.jsp" method="POST">
姓名：<input type="text" name="username" /><br/>
密码：<input type="password" name="password" /><br/>
<input type="submit" value="登陆"/>
</form>
<h4>表单提交到Servlet程序</h4>
<form action="/day12/user" method="POST">
姓名：<input type="text" name="username" /><br/>
密码：<input type="password" name="password" /><br/>
<input type="submit" value="登陆"/>
</form>
<h4>表单提交到Servlet（BeanUtils）程序</h4>
<form action="/day12/userBeanUtil" method="POST">
姓名：<input type="text" name="username" /><br/>
密码：<input type="password" name="password" /><br/>
剩余金额：<input type="text" name="money" /><br/>
生日：<input type="text" name="birthday" /><br/>
<input type="submit" value="登陆"/>
</form>
</body>
</html>success.jsp ( <jsp:setProperty>等指令实现bean的赋值)<%@page import="cn.itcast.vo.User"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h3>传统方式封装数据</h3>
<%
// 获取表单的内容
String username = request.getParameter("username");
String password = request.getParameter("password");
// 创建User对象。set设置值
User user = new User();
user.setUsername(username);
user.setPassword(password);
%>
<!-- 使用jsp的标签封装数据 -->
<jsp:useBean id="u" class="cn.itcast.vo.User"></jsp:useBean>
<jsp:setProperty property="*" name="u"/>
<jsp:getProperty property="username" name="u"/>
<jsp:getProperty property="password" name="u"/>
</body>
</html>
EL全名为Expression Language。EL主要作用：
| 关系运算符 | 说明 | 范例 | 结果 |
| == 或eq | 等于 | ${ 5 == 5 } 或${ 5 eq 5 } | true |
| != 或 ne | 不等于 | ${ 5 != 5 } 或 ${ 5 nq 5} | false |
| < 或 lt | 小于 | ${ 3 < 5 } 或 ${ 3 lt 5 } | true |
| > 或 gt | 大于 | ${ 3 > 5 } 或 ${ 3 gt 5 } | false |
| <= 或 le | 小于等于 | ${ 3 <= 5 } 或 ${ 3 le 5 } | true |
| >= 或 ge | 大于等于 | ${ 3 >= 5 } 或 ${ 3 ge 5 } | false |
| 逻辑运算符 | 说明 | 范例 | 结果 |
| && 或 and | 交集 | ${ A && B } 或 ${ A and B } | true/false |
| || 或 or | 并集 | ${ A || B } 或 ${ A or B } | true/false |
| ! 或 not | 非 | ${ !A } 或 ${ not A } | true/false |
<%
request.setAttribute("n1", 10);
request.setAttribute("n2", 20);
request.setAttribute("n3", 30);
request.setAttribute("n4", 40);
%>
<h3>算术运算</h3>
${ n1 + n2 }
<h3>关系运算</h3>
${n1 > n2 }${n1 gt n2 }<br/>
${n1 < n2 }${n1 ltn2 }<br/>
${n1 >= n2 }${n1 gen2 }<br/>
${n1 <= n2 }${n1 len2 }<br/>
${n1 == n2 }${n1 eqn2 }<br/>
${n1 != n2 }${n1 nen2 }<br/>
<h3>逻辑运算</h3>
${n1>n2 && n3>n4 }${n1>n2 and n3>n4 }<br/>
${n1>n2 || n3>n4 }${n1>n2 or n3>n4 }<br/>
${ !(n1>n2) }${not (n1>n2)}<br/>
EL表达式保留keyword
| 隐含对象名称 | 描写叙述 |
| pageContext | 相应于JSP页面中的pageContext对象（注意：取得是pageContext对象） |
| pageScope | 代表page域中用于保存属性的Map对象 |
| requestScope | 代表request域中用于保存属性的Map对象 |
| sessionScope | 代表session域中用于保存属性的Map对象 |
| applicationScope | 代表application域中用于保存属性的Map对象 |
| param | 表示一个保存了全部请求參数的Map对象 |
| paramValues | 表示一个保存了全部请求參数的Map对象。它对于某个请求參数。返回的是一个String[] |
| header | 表示一个保存了全部http请求字段的Map对象 |
| headerValues | 同上。返回String[] 数组。注意：假设头里面有"-" ，比如：Accept-Encoding,则 要使用headerValues["Accept-Encoding"] |
| cookie | 表示一个保存了全部cookie的Map对象 |
| initParam | 表示一个保存了全部web应用初始化參数的map对象 |
<%@page import="cn.itcast.vo.User2"%>
<%@page import="cn.itcast.vo.User"%>
<%@page import="java.util.HashMap"%>
<%@page import="java.util.Map"%>
<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>获取域对象中的值</h4>
<%
pageContext.setAttribute("name", "黄海波");
request.setAttribute("name", "美美");
%>
${ pageScope.name }
${ requestScope.name }
<h4>域中数组的值</h4>
<%
String [] arrs = {"美美","波波","东东","名名"};
request.setAttribute("arrs", arrs);
%>
${ arrs[2] }
<h4>域中集合的值</h4>
<%
List<String> list = new ArrayList<String>();
list.add("美美");
list.add("小凤");
list.add("芙蓉");
request.setAttribute("list", list);
%>
${ list[1] }
<h4>域中Map集合的值</h4>
<%
Map<String,String> map = new HashMap<String,String>();
map.put("aa", "美美");
map.put("bb", "小凤");
request.setAttribute("map", map);
%>
${ map.bb }
<h4>域中集合中有对象的值</h4>
<%
List<User2> uList = new ArrayList<User2>();
uList.add(new User2("banzhang","123"));
uList.add(new User2("美美","abc"));
request.setAttribute("uList", uList);
%>
${ uList[1].username }
</body>
</html>执行结果：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>EL的运算</h4>
<%
request.setAttribute("n1", 10);
request.setAttribute("n2", 20);
request.setAttribute("n3", 30);
request.setAttribute("n4", 40);
%>
<h4>加法运算</h4>
${ n1 + n2 }
<h3>关系运算</h3>
<h4>大于</h4>
${ n1 > n2 } ${ n1 gt n2 }
<h4>小于</h4>
${ n1 < n2 } ${ n1 lt n2 }
<h4>等于</h4>
${ n1 == n2 } ${ n1 eq n2 }
<h4>不等于</h4>
${ n1 != n2 } ${ n1 ne n2 }
<h4>大于等于</h4>
${ n1 >= n2 } ${ n1 ge n2 }
<h4>小于等于</h4>
${ n1 <= n2 } ${ n1 le n2 }
<h3>逻辑运算</h3>
<h4>与</h4>
${ n1 > n2 && n3 > n4 } ${ n1 > n2 and n3 > n4 }
<h4>或</h4>
${ n1 > n2 || n3 > n4 } ${ n1 > n2 or n3 > n4 }
<h4>非</h4>
${ !(n1 > n2) } ${ not (n1 > n2) }
</body>
</html>结果：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>EL的运算</h4>
<form action="/day12/el/elDemo4.jsp" method="POST">
姓名：<input type="text" name="username" /><br/>
<input type="submit" value="登陆"/>
</form>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h4>EL的WEB对象</h4>
${ param.username }
<h4>获取请求头</h4>
${ header.referer }
<h4>获取全局初始化參数</h4>
${ initParam.username }
<h4>pageContext对象</h4>
${ pageContext.request.contextPath }
</body>
</html>执行结果：
JAVAWEB开发之Session的追踪创建和销毁、JSP具体解释（指令，标签，内置对象，动作即转发和包括）、JavaBean及内省技术以及EL表达式获取内容的使用
标签：创建 users 不同 cookie对象 实现 script 忽略 r.js unit
原文地址：http://www.cnblogs.com/blfbuaa/p/7389040.html
