JSP学习笔记2

《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="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() %>&nbsp;&nbsp;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="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="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() %>&nbsp;&nbsp;价格:<%=i.getPrice() %> ￥ </dd> 
                  </dl>
              </div>
              <!-- 循环结束 -->
              <%
                  }
              }
               %>
              </td>
        </tr>
      </table>
    </center>
  </body>
</html>
details
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原文地址：https://www.cnblogs.com/wenruo/p/6238409.html