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动态网页技术--JSP（1）

一.JSP

jsp:网页文件 html + java

Jsp的生命周期（第一次访问时稍慢）:

1.创建jsp文件之后

2.Tomcat将jsp翻译成java文件（servlet）

3.将java文件编译生成文件(work文件夹)

4.加载类实例化类 init service destroy

Jsp的页面构成:

1.html

2.指令标记<%@ %>

– page：用于定义JSP页面的某些属性，翻译时起作用，作用在整个JSP文件，与放置的位置无关

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

– include：JSP可以通过include指令来包含其他文件。被包含的文件可以是JSP文件、HTML文件或文本文件

<%@ include file="login.jsp" %>

– taglib：声明此JSP文件使用了自定义的标签，同时引用标签库，也指定了他们的标签的前缀

<%@ taglib uri="http://www.jspcentral.com/tags" prefix="public" %>

3.脚本段 <% java %>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

4. 表达式 (执行结果并输出显示到页面上) <%= 变量名/方法的调用 %>

5.注释 <! -- 会显示在客户端 -->

<%-- 不会显示在客户端 --%>

6.声明 <%! 方法 %>

声明的方法在翻译时被加载，在调用时才生效

7.动作 ---封装了一些有固定功能的java代码

<jsp: >

8.EL表达式 ---- 获取值

9.JSTL标签库 ----- -封装了一些有固定功能的java代码

<c:if >

10.内置对象 (9个)

out---向网页输出内容

request---接收请求(一次请求)

response---返回响应

session---会话对象---在多个页面之间共享值

application---应用对象

page---指向当前JSP页面本身

exception---例外对象

pageContext---提供了对JSP页面内所有的对象及名字空间的访问

config---在一个Servlet初始化时，JSP引擎向它传递信息用的

11.pageContext:可以取其他作用域内的值

findAttribute方法可以按照作用域由小到大的顺序取值

pageContext request session application

当前页面一次请求整个会话整个应用

cookie存值:客户端存值 (浏览器上磁盘上)

(不属于内置对象) (string,string)--key对应value方式存值--存string类型值

使用时需要创建cookie对象--new

回显之前设置有效期：记录的时间

session存值：服务器端存值

(string,object)--key对应value方式存值--存object类型值

jsp的内置对象，直接使用

有效期：发呆时

•需求：MyJsp2.jsp显示当前时间，通过地址栏，复选框，文本框向MyJsp3.jsp页面传值

 1  MyJsp2.jsp 
   <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 2 <%@page import="java.text.SimpleDateFormat"%>
 3 <%@page import="sun.net.www.content.text.plain"%>
 4  <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
10 <html>
11   <head>
12     <base href="<%=basePath%>">
13     
14     <title>My JSP 'MyJsp2.jsp' starting page</title>
15     
16     <meta http-equiv="pragma" content="no-cache">
17     <meta http-equiv="cache-control" content="no-cache">
18     <meta http-equiv="expires" content="0">    
19     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
20     <meta http-equiv="description" content="This is my page">
21     <!--
22     <link rel="stylesheet" type="text/css" href="styles.css">
23     -->
24 
25   </head>
26 
27   <body>
28                   <font>时间</font>
29 <%!
30 
31          public String  getTime(){
32 
33                     Date d1=new Date();
34            SimpleDateFormat sdf= new SimpleDateFormat("yyyy/MM/dd");
35                  String time=sdf.format(d1);
36          return time;
37 }
38  %>
39            <%=getTime() %>
40   
41   
42    <form action="MyJsp3.jsp?a=1" method="post">
43                <input type="text" name="t"/>
44           隐藏域<input type="hidden" name="hi" value="隐藏域"/><br>
45                <input type="checkbox" name="boxs" value="篮球"/>篮球<br/>
46                <input type="checkbox" name="boxs" value="足球"/>足球<br/>
47                <input type="checkbox" name="boxs" value="乒乓球"/>乒乓球<br/>
48                <input type="checkbox" name="boxs" value="橄榄球"/>橄榄球<br/>
49                <input type="checkbox" name="boxs" value="羽毛球"/>羽毛球<br/>
50                <input type="submit" value="提交数据"/>
51     </form>
52  </body>
53 </html>

 1 MyJsp3.jsp
   <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 2 <%
 3 String path = request.getContextPath();
 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 5 %>
 6 
 7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 8 <html>
 9   <head>
10     <base href="<%=basePath%>">
11     
12     <title>My JSP 'MyJsp3.jsp' starting page</title>
13     
14     <meta http-equiv="pragma" content="no-cache">
15     <meta http-equiv="cache-control" content="no-cache">
16     <meta http-equiv="expires" content="0">    
17     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
18     <meta http-equiv="description" content="This is my page">
19     <!--
20     <link rel="stylesheet" type="text/css" href="styles.css">
21     -->
22 
23   </head>
24   
25   <body>
26    <%
27                  request.setCharacterEncoding("utf-8");
28                  response.setContentType("text/html;charset=utf-8");    
29                  String a =request.getParameter("a");
30                  String box[]=request.getParameterValues("boxs");
31                  String t =request.getParameter("t");
32                  for(int i=0;i<box.length;i++){
33    
34    %>
35    
36                   <%=box[i] %><br>
37    <%
38    
39     }
40     
41     %>
42     
43     
44     <br/><%=t%><br/>
45     <font style="color:red">传递的变量a的值为:<%=a%></font>
46   </body>
47 </html>

跳转后结果

多个页面之间共享值:

1. 表单---传递String类型的值

隐含表单（隐藏域）hidden---传递String类型的值

2.地址？名=值 ---传递String类型的值

3.session:---在一次会话范围内的多个页面之间共享值

一次会话:从该用户第一次登录开始，到安全退出结束

存值和取值:key ----- value (Object)

Session有效期: (发呆时间,空闲时间)

tomcat下可以配置session的时效

配置路径：Tomcat---conf----web.xml

<session-config>

<session-timeout>30</session-timeout> 30分钟

</session-config>

session存值：

       <%
       //session发呆时间是10秒,参数为0代表销毁
       session.setMaxInactiveInterval(10);     
       //向session作用域内存值
       session.setAttribute("name","Pioneer.HengYu");
       //SessionID  -----  区分不同的用户
       out.println(session.getId());
       %>

session取值：

       <%
       String str=(String)session.getAttribute("name");
       out.println(str);
       %>

•需求：用session，三个页面传obj类型值

 1 Session1页面
 2 
 3 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 4 <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
10 <html>
11   <head>
12     <base href="<%=basePath%>">
13     
14     <title>My JSP 'Session.jsp' starting page</title>
15     
16     <meta http-equiv="pragma" content="no-cache">
17     <meta http-equiv="cache-control" content="no-cache">
18     <meta http-equiv="expires" content="0">    
19     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
20     <meta http-equiv="description" content="This is my page">
21     <!--
22     <link rel="stylesheet" type="text/css" href="styles.css">
23     -->
24 
25   </head>
26   
27   <body>
28      这里是session1
29      <a href="session/Session2.jsp">点击跳转</a>
30      <%
31      //session发呆时间是10秒,参数为0代表销毁
32      session.setMaxInactiveInterval(10);     
33      //向session作用域内存值
34      session.setAttribute("name","里2");
35      //SessionID  -----  区分不同的用户
36      out.println(session.getId());
37       %>
38        <%
39     String str=(String)session.getAttribute("name");
40     out.println(str);
41      %>
42   </body>
43 </html>

 1 Session2页面
 2 
 3 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 4 <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
10 <html>
11   <head>
12     <base href="<%=basePath%>">
13     
14     <title>My JSP 'Session2.jsp' starting page</title>
15     
16     <meta http-equiv="pragma" content="no-cache">
17     <meta http-equiv="cache-control" content="no-cache">
18     <meta http-equiv="expires" content="0">    
19     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
20     <meta http-equiv="description" content="This is my page">
21     <!--
22     <link rel="stylesheet" type="text/css" href="styles.css">
23     -->
24 
25   </head>
26   
27   <body>
28     这里是session2
29     <a href="session/Session3.jsp">点击跳转</a>
30    
31     <%
32     String str=(String)session.getAttribute("name");
33     out.println(session.getId());
34     out.println(str);
35      
36      %>
37   </body>
38 </html>

 1 Session3页面
 2 
 3 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 4 <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
10 <html>
11   <head>
12     <base href="<%=basePath%>">
13     
14     <title>My JSP 'Session3.jsp' starting page</title>
15     
16     <meta http-equiv="pragma" content="no-cache">
17     <meta http-equiv="cache-control" content="no-cache">
18     <meta http-equiv="expires" content="0">    
19     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
20     <meta http-equiv="description" content="This is my page">
21     <!--
22     <link rel="stylesheet" type="text/css" href="styles.css">
23     -->
24 
25   </head>
26   
27   <body>
28  这里是session3
29   <%
30     String str=(String)session.getAttribute("name");
31     out.println(session.getId());
32     out.println(str);
33      %>
34   </body>
35 </html>

运行结果

•需求: 普通用户的登录，如果用户直接访问主页，将该用户踢回登录页面 –防止非法登录

验证:1.先把生成的uuid存入session中

2.取用户输入的验证码

3.判断

文件路径

 1 登录页面
 2 
 3 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
 4 <%
 5     String path = request.getContextPath();
 6     String basePath = request.getScheme() + "://"
 7             + request.getServerName() + ":" + request.getServerPort()
 8             + path + "/";
 9 %>
10 
11 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
12 <html>
13     <head>
14         <base href="<%=basePath%>">
15 
16         <title>登录页</title>
17 
18         <meta http-equiv="pragma" content="no-cache">
19         <meta http-equiv="cache-control" content="no-cache">
20         <meta http-equiv="expires" content="0">
21         <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
22         <meta http-equiv="description" content="This is my page">
23         <!--
24     <link rel="stylesheet" type="text/css" href="styles.css">
25     -->
26 
27     </head>
28 
29     <body>
30         <form action="UserServlet" method="post" >
31             用户名
32             <input type="text" name="name">
33             <br />
34             密码
35             <input type="password" name="psw" />
36             <br />
37             验证码
38              <input type="text" name="clientCheck"/>
39              <img  src="http://localhost:8088/myJsp/CheckImg"/>
40              <br/>
41             <input type="submit" value="登录"/>
42 
43         </form>
44     </body>
45 </html>

 1 创建一个Servlet，对用户的处理起名UserServlet
 2 
 3 package com.neusoft.login;
 4 
 5 import java.io.IOException;
 6 import java.io.PrintWriter;
 7 
 8 import javax.servlet.ServletException;
 9 import javax.servlet.http.HttpServlet;
10 import javax.servlet.http.HttpServletRequest;
11 import javax.servlet.http.HttpServletResponse;
12 import javax.servlet.http.HttpSession;
13 
14 public class UserServlet extends HttpServlet {
15 
16     public void doGet(HttpServletRequest request, HttpServletResponse response)
17             throws ServletException, IOException {
18         this.doPost(request, response);
19     }
20 
21     public void doPost(HttpServletRequest request, HttpServletResponse response)
22             throws ServletException, IOException {
23         // 设置字符集
24         request.setCharacterEncoding("utf-8");
25         response.setContentType("text/html;charset=utf-8");
26         
27         
28         // 获取用户名和密码,验证码
29         String name = request.getParameter("name");
30         String psw = request.getParameter("psw");
31         String  clientCheck=request.getParameter("clientCheck");  //自己输入取到的值
32         
33         
34         // 判断是否正确:正确---index 错误----fail  判断验证码是否正确
35         HttpSession session = request.getSession();
36         session.setMaxInactiveInterval(30); // 有效期30秒
37         String   serverCheck=(String)session.getAttribute("serverCheck");  //验证码生成的值
38         
39         
40         if(!clientCheck.equals(serverCheck)){
41                 response.getWriter().print("验证码有误");
42                 response.setHeader("refresh", "3;url=http://localhost:8088/myJsp/login/Login.jsp");//验证码有误3秒返回登录页面
43             
44         }else  if (name.equals("Pioneer.HengYu") && psw.equals("123")) {
45             // 将name的值存入session作用域中
46             session.setAttribute("name", name);
47             request.getRequestDispatcher("index.jsp").forward(request, response);
48         } else {
49             response.sendRedirect("fail.jsp");
50         }
51 
52     }
53 
54 }

 1 index.jsp
 2 
 3 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
 4 <%
 5 String path = request.getContextPath();
 6 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 7 %>
 8 
 9 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
10 <html>
11   <head>
12     <base href="<%=basePath%>">
13     
14     <title>主页</title>
15     <meta http-equiv="pragma" content="no-cache">
16     <meta http-equiv="cache-control" content="no-cache">
17     <meta http-equiv="expires" content="0">    
18     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
19     <meta http-equiv="description" content="This is my page">
20     <!--
21     <link rel="stylesheet" type="text/css" href="styles.css">
22     -->
23   </head>
24   
25   <body>
26                 <!--防止非法登录，不输入账号点登录，直接跳回主页-->
27            <% 
28              if(session.getAttribute("name")==null){
29                      response.sendRedirect("login/Login.jsp");
30              } 
31             %>
32   
33              <%
34               out.println(UUID.randomUUID().toString());
35               %>
36         <h1>欢迎<%=session.getAttribute("name")%>登录</h1>  
37   
38   </body>
39 </html>

 1 验证码图片的类
 2 
 3 package com.neusoft.login;
 4 
 5 
 6 
 7 import java.awt.Color;
 8 import java.awt.Font;
 9 import java.awt.Graphics;
10 import java.awt.image.BufferedImage;
11 import java.io.IOException;
12 import java.util.Random;
13 import java.util.UUID;
14 
15 import javax.imageio.ImageIO;
16 import javax.servlet.ServletException;
17 import javax.servlet.http.HttpServlet;
18 import javax.servlet.http.HttpServletRequest;
19 import javax.servlet.http.HttpServletResponse;
20 import javax.servlet.http.HttpSession;
21 /**
22  * 生成随机图片(验证码)
23  *
24  */
25 public class CheckImg extends HttpServlet {
26 
27     public void doGet(HttpServletRequest request, HttpServletResponse response)
28             throws ServletException, IOException {
29 
30         //生成验证码的背景图片
31         BufferedImage image = new BufferedImage(70, 25, 
32                                                 BufferedImage.TYPE_INT_RGB) ;
33         
34         //通过画笔类向背景上画内容
35         Graphics g = image.getGraphics();
36         g.setColor(Color.YELLOW);
37         g.setFont(new Font("黑体",Font.BOLD,20));
38         
39         //生成验证码
40         String uuid = UUID.randomUUID().toString();
41         uuid = uuid.substring(0,4);
42         
43         
44         //把生成的随机内容保存到 session 会话作用域中
45         HttpSession session = request.getSession();
46         session.setAttribute("serverCheck", uuid);
47         
48         //画图
49         g.drawString(uuid, 15, 20);
50         
51         //生成图片的干扰线条
52         for(int i=0;i < 5;i++) {
53             g.setColor(Color.red);
54             g.drawLine(new Random().nextInt(60),
55                        new Random().nextInt(15),
56                        new Random().nextInt(60)+10, 
57                        new Random().nextInt(15)+10);
58         }
59         
60         
61         ImageIO.write(image, "JPG", response.getOutputStream());
62     }
63 
64 }

 1 web.xml中配置
 2 
 3 <?xml version="1.0" encoding="UTF-8"?>
 4 <web-app version="2.5" 
 5     xmlns="http://java.sun.com/xml/ns/javaee" 
 6     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 7     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 8     http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 9   <servlet>
10     <servlet-name>UserServlet</servlet-name>
11     <servlet-class>com.neusoft.login.UserServlet</servlet-class>
12   </servlet>
13 
14   <servlet-mapping>
15     <servlet-name>UserServlet</servlet-name>
16     <url-pattern>/UserServlet</url-pattern>
17   </servlet-mapping>
18   <welcome-file-list>
19     <welcome-file>index.jsp</welcome-file>
20   </welcome-file-list>
21   
22   <servlet>
23       <servlet-name>CheckImg</servlet-name>
24       <servlet-class>com.neusoft.login.CheckImg</servlet-class>
25   </servlet>
26   <servlet-mapping>
27      <servlet-name>CheckImg</servlet-name>
28      <url-pattern>/CheckImg</url-pattern>
29   </servlet-mapping>
30   
31   
32 </web-app>

执行结果

主页

填写正确跳转

账号密码填错，验证码填对跳转

验证码填错，3秒返回Loogin.jsp

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原文地址：https://www.cnblogs.com/Pioneer-HengYu/p/6641619.html