《JAVA遇见HTML——JSP篇》学习笔记（下）
1.Javabean
Javabeans就是符合某种规范的java类，使用Javabeans的好处是【解决代码的重复编写】，减少代码冗余，功能区分明确，提高代码的维护性。
设计原则（规范）：1.公有类 2.属性私有 3.包含无参的共有构造方法 4.getter和setter方法封装属性
JSP动作元素（action element）：
JSP动作元素为请求处理阶段提供信息。动作元素遵循XML语法，有一个包含元素名的开始标签，可以有属性，可选的内容、与开始标签匹配的结束标签。
第一类是与存取JavaBean有关，包括： <jsp:useBean> <jsp:setProperty> <jsp:getProperty>
<jsp:useBean id="标识符" class="实例化的类的完整名称" scope="作用范围" /> id可以理解为创建的类的对象的名字
<jsp:setProperty name="JavaBean实例名" property="*" /> （跟表单相关联）自动匹配所有属性
<jsp:setProperty name="JavaBean实例名" property="JavaBean属性名" /> （跟表单相关联）
<jsp:setProperty name="JavaBean实例名" property="JavaBean属性名" value="BeanValue" /> （手工设置）
<jsp:setProperty name="JavaBean实例名" property="JavaBean属性名" param="request对象中的参数名" /> （跟request参数相关联）URL地址栏传递
<jsp:getProperty name="" property="">
<body>
<jsp:useBean id="myUser" class="com.po.User" scope="request" />
<%-- <jsp:setProperty property="*" name="myUser"/> --%>
<%-- <jsp:setProperty property="username" name="myUser"/> --%>
<jsp:setProperty property="username" name="myUser" value="xiaobai"/>
<jsp:setProperty property="password" param="pwd" name="myUser"/>
用户名：<%=myUser.getUsername()%><br>
密码：<%=myUser.getPassword()%>
</body>
javabean
Javabean四个作用域范围：
page,request,session,application
<jsp:getProperty>标签调用时，将会按照page、request、session和application的顺序来查找这个JavaBean实例，直至找到一个实例对象为止，如果在这4个范围内都找不到JavaBean实例，则抛出异常。
<body>
<jsp:useBean id="myUser" class="com.po.User" scope="page"></jsp:useBean>
用户名：<jsp:getProperty property="username" name="myUser"/>
密码：<jsp:getProperty property="password" name="myUser"/>
<hr>
<%-- 用户名:<%=((User)application.getAttribute("myUser")).getUsername() %> --%>
<%-- 密码:<%=((User)application.getAttribute("myUser")).getPassword() %> --%>
<%-- 用户名:<%=((User)session.getAttribute("myUser")).getUsername() %> --%>
<%-- 密码:<%=((User)session.getAttribute("myUser")).getPassword() %> --%>
<%-- 用户名:<%=((User)request.getAttribute("myUser")).getUsername() %> --%>
<%-- 密码:<%=((User)request.getAttribute("myUser")).getPassword() %> --%>
用户名:<%=((User)pageContext.getAttribute("myUser")).getUsername() %>
密码:<%=((User)pageContext.getAttribute("myUser")).getPassword() %>
</body>
testScope
Model1
三层结构：界面层（jsp页面） 业务逻辑层（javabean） 数据层（数据库）
就是将业务逻辑封装起来而不是全部写在JSP界面。
package com.dao;
import com.po.Users;
public class UsersDao {
public boolean usersLogin(Users u) {
if ("admin".equals(u.getUsername()) && "admin".equals(u.getPassword()))
return true;
return false;
}
}
com.dao;
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<jsp:useBean id="loginUser" class="com.po.Users" scope="page"/>
<jsp:useBean id="userDao" class="com.dao.UsersDao" scope="page"/>
<jsp:setProperty property="*" name="loginUser"/> <%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; request.setCharacterEncoding("utf-8"); if (userDao.usersLogin(loginUser)) {
session.setAttribute("username", loginUser.getUsername());
request.getRequestDispatcher("login_success.jsp").forward(request, response); } else {
response.sendRedirect("login_failure.jsp");
}
%>
dologin.jsp
2.JSP状态管理
HTTP协议的无状态性：无状态是指，当浏览器发送请求给服务器的时候，服务器会响应。但当同一个浏览器再次发送请求时，服务器不会知道是刚才那个浏览器。简单说就是服务器不会保存用户状态，不会记得客户端是否访问过，所以这就是无状态协议
保存用户状态的两大机制：1.Session 2.Cookie
Cookie是文本信息，保存在客户端。
作用：1.保存用户对象的追踪； 2.保存用户网页浏览记录与习惯； 3.简化登录；
but有泄露用户隐私的风险
创建与使用Cookie：
创建Cookie对象： Cookie cookie=new Cookie(String key,Object value);
写入Cookie： response.addCookie(cookie);
读取Cookie： Cookie[] cookies=request.getCookies();
setMaxAge( expiry ) 设置cookie的有效期，以秒为单位
getMaxAge() 获取cookie的有效时间，以秒为单位
setValue(String value) 在cookie创建后，对cookie进行赋值
getValue() 获取cookie的值
getName() 获取cookie的名称
<%@page import="java.net.URLDecoder"%>
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'login.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
--> </head> <%
request.setCharacterEncoding("utf-8");
String username = "";
String password = "";
Cookie[] cookies = request.getCookies();
if (cookies != null && cookies.length > 0) {
for (Cookie c: cookies) {
if ("username".equals(c.getName())) {
username = URLDecoder.decode(c.getValue(), "utf-8");
}
if ("password".equals(c.getName())) {
password = URLDecoder.decode(c.getValue(), "utf-8");
}
}
}
%> <body>
<h1>用户登录</h1>
<hr>
<form name="loginForm" action="dologin.jsp" method="post">
<table>
<tr>
<td>用户名：</td>
<td><input type="text" name="username" value="<%=username%>"/></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="password" value="<%=password%>"/></td>
</tr>
<tr>
<td colspan="2"><input type="checkbox" name="isUseCookie" checked="checked"/>
十天内记住登录状态
</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" value="登录"/><input type="reset" value="取消"/></td>
</tr>
</table>
</form>
</body>
</html>
login.jsp
<%@ page language="java" import="java.util.*,java.net.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'dologin.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
--> </head> <body>
<h1>登录成功</h1>
<hr>
<br>
<%
request.setCharacterEncoding("utf-8");
String[] isUserCookies = request.getParameterValues("isUseCookie");
if (isUserCookies != null && isUserCookies.length > 0) {
//使用URLEncoder解决无法在Cookie当中保存中文字符串问题
String username = URLEncoder.encode(request.getParameter("username"),"utf-8");
String password = URLEncoder.encode(request.getParameter("password"),"utf-8"); Cookie usernameCookie = new Cookie("username", username);
Cookie passwordCookie = new Cookie("password", password);
usernameCookie.setMaxAge(864000);//10 days
passwordCookie.setMaxAge(864000);
response.addCookie(usernameCookie);
response.addCookie(passwordCookie);
} else {
Cookie[] cookies = request.getCookies();
if (cookies != null && cookies.length > 0) {
for (Cookie c: cookies) {
if (c.getName().equals("username") || c.getName().equals("password")) {
c.setMaxAge(0);
response.addCookie(c);
}
}
}
}
%>
<a href="users.jsp" target="_blank">查看用户信息</a> </body>
</html>
dologin.jsp
<%@ page language="java" import="java.util.*, java.net.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'users.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
--> </head> <body>
<h1>用户信息</h1>
<hr>
<%
request.setCharacterEncoding("utf-8");
String username="";
String password = "";
Cookie[] cookies = request.getCookies();
if(cookies!=null&&cookies.length>0)
{
for(Cookie c:cookies)
{
if(c.getName().equals("username"))
{
username = URLDecoder.decode(c.getValue(),"utf-8");
}
if(c.getName().equals("password"))
{
password = URLDecoder.decode(c.getValue(),"utf-8");
}
}
}
%>
<BR>
<BR>
<BR>
用户名：<%=username %><br>
密码：<%=password %><br>
</body>
</html>
users.jsp
Cookie和Session的区别
3.JSP指令与动作
include指令： <%@ include file="URL"%>
include动作： <jsp:include page="URL" flush="true|false" /> flush是否从缓冲区读取。
（ps:import里面不要加分号 ~~~>_<~~~
forward动作： <jsp:forward page="URL" />
等同于： request.getRequestDispatcher("/url").forward(request,response);
param动作： <jsp:param name="参数名" value="参数值">
常常与<jsp:forward>一起使用，作为其子标签，可以复制给已有参数，也可以添加新的参数。
<jsp:forward page="user.jsp">
<jsp:param value="admin@123.net" name="email"/>
<jsp:param value="xiaoshagua" name="username"/>
</jsp:forward>
tomcat高版本：response.addCookie(cookie)会报java.lang.IllegalArgumentException；因为Cookie对象的构造函数的两个字符串参数：Cookie名字和Cookie值都不能包含空白字符以及下列字符：[ ] ( ) < > = , " / ? @ : 具体改detials.jsp中的，将+“，”改为加"#";
package dao; import java.sql.*;
import java.util.ArrayList; import entity.Items;
import util.DBHelper; // 商品的业务逻辑类
public class ItemsDAO {
// 展示所有商品信息
public ArrayList<Items> getAllItems() {
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
ArrayList<Items> list = new ArrayList<Items>();
try {
conn = DBHelper.getConnection();
String sql = "Select * from items;";
stmt = conn.prepareStatement(sql);
rs = stmt.executeQuery();
while (rs.next()) {
Items items = new Items();
items.setId(rs.getInt("id"));
items.setName(rs.getString("name"));
items.setCity(rs.getString("city"));
items.setNumber(rs.getInt("number"));
items.setPicture(rs.getString("picture"));
items.setPrice(rs.getInt("price"));
list.add(items); // 商品加入集合
}
return list;
} catch (Exception ex) {
ex.printStackTrace();
return null;
} finally {
try {
if (rs != null) rs.close();
if (stmt != null) stmt.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
}
} public Items getItemById(int id) { Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null; try {
conn = DBHelper.getConnection();
String sql = "Select * from items where id = ?;"; stmt = conn.prepareStatement(sql);
stmt.setInt(1, id);
rs = stmt.executeQuery();
if (rs.next()) {
Items items = new Items();
items.setId(rs.getInt("id"));
items.setName(rs.getString("name"));
items.setCity(rs.getString("city"));
items.setNumber(rs.getInt("number"));
items.setPicture(rs.getString("picture"));
items.setPrice(rs.getInt("price"));
return items;
}
return null;
} catch (Exception ex) {
ex.printStackTrace();
return null;
} finally {
try {
if (rs != null) rs.close();
if (stmt != null) stmt.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
}
}
//最近浏览的商品细信息
public ArrayList<Items> getViewList(String list) {
ArrayList<Items> itemlist = new ArrayList<Items>();
if (list != null && list.length() > 0) {
String arr[] = list.split("#");
for (int i = arr.length-1; i >= 0 && i >= arr.length-5; i--) {
int id = Integer.parseInt(arr[i]);
itemlist.add(getItemById(id));
}
return itemlist;
}
return null;
} public static void main(String[] args) {
ItemsDAO i = new ItemsDAO();
i.getViewList("1#4#6");
} }
ItemsDAO
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%@ page import="dao.ItemsDAO" %>
<%@ page import="entity.Items" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<style type="text/css">
div{
float:left;
margin: 10px;
}
div dd{
margin:0px;
font-size:10pt;
}
div dd.dd_name
{
color:blue;
}
div dd.dd_city
{
color:#000;
}
</style>
</head> <body>
<h1>商品展示</h1>
<hr>
<center>
<table width="750" height="60" cellpadding="0" cellspacing="0" border="0">
<tr>
<td>
<!-- 商品循环开始 -->
<%
ItemsDAO itemsDAO = new ItemsDAO();
ArrayList<Items> list = itemsDAO.getAllItems();
if (list != null && list.size() > 0)
for (int i = 0; i < list.size(); i++) {
Items item = list.get(i);
%> <div>
<dl>
<dt>
<a href="details.jsp?id=<%=item.getId() %>"><img src="data:images/<%=item.getPicture()%>" width="120" height="90" border="1"/></a>
</dt>
<dd class="dd_name"><a href="details.jsp?id=<%=item.getId() %>"><%=item.getName() %></a></dd>
<dd class="dd_city">产地：<%=item.getCity() %> 价格:￥<%=item.getPrice() %></dd>
</dl>
</div> <%
}
%>
</table>
</center>
</body>
</html>
index.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8" %>
<%@ page import="entity.Items"%>
<%@ page import="dao.ItemsDAO"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'details.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<style type="text/css">
div{
float:left;
margin-left: 30px;
margin-right:30px;
margin-top: 5px;
margin-bottom: 5px;
}
div dd{
margin:0px;
font-size:10pt;
}
div dd.dd_name
{
color:blue;
}
div dd.dd_city
{
color:#000;
}
</style>
</head> <body>
<h1>商品详情</h1>
<hr>
<center>
<table width="750" height="60" cellpadding="0" cellspacing="0" border="0">
<tr>
<!-- 商品详情 -->
<%
ItemsDAO itemDao = new ItemsDAO();
Items item = itemDao.getItemById(Integer.parseInt(request.getParameter("id")));
if(item!=null)
{
%>
<td width="70%" valign="top">
<table>
<tr>
<td rowspan="4"><img src="data:images/<%=item.getPicture()%>" width="200" height="160"/></td>
</tr>
<tr>
<td><B><%=item.getName() %></B></td>
</tr>
<tr>
<td>产地：<%=item.getCity()%></td>
</tr>
<tr>
<td>价格：<%=item.getPrice() %>￥</td>
</tr>
</table>
</td>
<%
} else {
out.print("null!");
}
%>
<!-- 循环结束 --> <%
String list = "";
// 从客户端获取Cookie集合
Cookie[] cookies = request.getCookies();
// 遍历 是否存在ListViewCookie
if (cookies != null && cookies.length > 0) {
for (Cookie c: cookies) {
if (c.getName().equals("ListViewCookie")) {
list = c.getValue();
}
}
} list += request.getParameter("id") + "#";
// 浏览记录过多清零
String arr[] = list.split("#");
if (arr != null && arr.length >= 1000) {
list = "";
}
// 存在同名的Cookie会覆盖前一个
Cookie cookie = new Cookie("ListViewCookie", list);
response.addCookie(cookie); %>
<!-- 浏览过的商品 -->
<td width="30%" bgcolor="#EEE" align="center">
<br>
<b>您浏览过的商品</b><br>
<!-- 循环开始 -->
<%
ArrayList<Items> itemlist = itemDao.getViewList(list);
if (itemlist != null && itemlist.size() > 0) {
for (Items i: itemlist) { %>
<div>
<dl>
<dt>
<a href="details.jsp?id=<%=i.getId()%>"><img src="data:images/<%=i.getPicture() %>" width="120" height="90" border="1"/></a>
</dt>
<dd class="dd_name"><%=i.getName() %></dd>
<dd class="dd_city">产地:<%=i.getCity() %> 价格:<%=i.getPrice() %> ￥ </dd>
</dl>
</div>
<!-- 循环结束 -->
<%
}
}
%>
</td>
</tr>
</table>
</center>
</body>
</html>
details