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

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]);
}
}
}

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);

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;
	}
	
}

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;
	}

}

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);
	}

}

package 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);
	}

}

<%@ 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>

<%@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>

<%
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/>

<%@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>

<%@ 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>

<%@ 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>