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  • 新手学Html之JSP基础语法——入门（二）

    JSP基础语法

    JSP注释

    comment.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <!-- 这个注释客户端可以看见 -->
11     <%-- jsp中的注释，客户端无法看见 --%>
12     <%
13         //java中的单行注释，客户端无法看见
14         /*
15             java中的多行注释，客户端无法看见
16         */
17     %>
18 </body>
19 </html>
    View Code

    Scriptlet

    scriptlet_demo01.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <%
11         //定义局部变量，编写语句
12         int x = 10;
13         String info = "www.mldnjava.cn";
14         out.println("<h2>x="+x+"</h2>");
15         out.println("<h2>info="+info+"</h2>");
16     %>
17 </body>
18 </html>
    View Code

    scriptlet_demo02.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <!-- 定义全局变量，方法，类 -->
11     <%! public static final String INFO = "www.mldnjava.cn"; %>
12     <!-- 用于输出一个变量或一个具体的常量 -->
13     <%=1 %><br/>
14     <%=INFO %>
15 </body>
16 </html>
    View Code

    尽量不要使用system.out.print();进行输出

    input_table_value.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <form action="print_table.jsp" method="post">
11         <table border="1" width="100%">
12             <tr>
13                 <td>输入表格的行数：</td>
14                 <td><input type="text" name="row"></td>
15             </tr>
16             <tr>
17                 <td>输入表格的列数：</td>
18                 <td><input type="text" name="col"></td>
19             </tr>
20             <tr>
21                 <td>
22                     <input type="submit" value="显示">
23                     <input type="reset" value="重置">
24                 </td>
25             </tr>
26         </table>
27     </form>
28 </body>
29 </html>
    View Code

    print_table.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <%
11         int rows = 0;
12         int cols = 0;
13         //读取input_table_value.jsp   post的row和col，将之强制转换为int类型
14         try{
15             rows = Integer.parseInt(request.getParameter("row"));
16             cols = Integer.parseInt(request.getParameter("col"));
17         }catch(Exception e){}
18         if(rows>0&&cols>0){
19     %>
20             <table border="1" width="100%">
21             <%
22                 for(int x = 1;x <= rows; x++){
23             %>
24                 <tr>
25             <%
26                     for(int y = 1; y <= cols; y++){ 
27             %>
28                         <td> <%=x%> * <%=y%> = <%=(x * y)%></td>
29             <%
30                     }
31             %>
32                 </tr>
33             <%
34                 }
35             %>
36             </table>
37             <a href="input_table_value.jsp"><input type="button" value="返回"></a>
38     <%
39         }else{
40     %>
41             <%--输入不符合时弹出对话框指示，并自动返回到输入数值处 --%>
42             <script type="text/javascript" language="javascript">
43                 alert("输入不合法！");
44                 /* alert(document.location === window.location);//true */
45                 //window.location.href="input_table_value.jsp";
46                 //document.location.href="input_table_value.jsp";
47                 //以上两种好像等价，待探索
48                 window.document.location.href="input_table_value.jsp";
49             </script>
50     <%
51             }
52     %>
53 </body>
54 </html>
    View Code

    scriptlet标签

    此标签具有和<% %>一样的效果，更加美观一些，无强制要求

    scriptlet_tag.jsp

    1 <jsp:scriptlet>
2     String url = "www.MLDNJAVA.cn";
3 </jsp:scriptlet>
4 <h2><%=url %></h2>
    View Code

    page指令

    设置页面的MIME、文件编码

    page_demo01.jsp

     1 <%@ page language="java" contentType="application/msword; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <!-- pageEncoding是JSP文件本身的编码，contentType是服务器发送给客户端的内容编码 -->
11     
12     <!--        txt     text/plain -->
13     <!--        doc     application/msword -->
14     <!--        png     image/png -->
15     <!--    jpg/jpeg    image/jpeg -->
16     <!--    htm/html    text/html-->
17     <table border="1">
18         <%
19             //指定文件下载后的保存名称是mldn.doc
20             response.setHeader("Content-Disposition", "attachment;filename=mldn.doc");
21         %>
22         <tr><td>欢迎大家</td></tr>
23         <tr><td>欢迎大家！！</td></tr>
24         <tr><td>欢迎大家！！！</td></tr>
25     </table>
26 </body>
27 </html>
    View Code

    错误页的设置

    服务器端跳转

    show_error.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <%@ page errorPage="error.jsp" %>
 4 <%-- 出现错误将会跳转到error.jsp --%>
 5 ​
 6 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 7 <html>
 8 <head>
 9 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
10 <title>Insert title here</title>
11 </head>
12 <body>
13     <%
14         int result = 10 / 0;
15     %>
16     <%=result %>
17 </body>
18 </html>
    View Code

    error.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <%@ page isErrorPage="true" %>
 4 <%-- 表示出现错误该页面可以处理错误 --%>
 5 <% response.setStatus(200); %>
 6 <%-- 设置了200的HTTP状态码，表示本页没有错误，防止tomcat也认为本页出现了错误，从而无法显示 --%>
 7 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 8 <html>
 9 <head>
10 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
11 <title>Insert title here</title>
12 </head>
13 <body>
14     <h1>程序出现了错误！</h1>
15 </body>
16 </html>
    View Code

    数据库连接操作

    page指令使用import导入所需要的Java开发包

    mldn.sql

     1 /*
 2 Navicat MySQL Data Transfer
 3 ​
 4 Source Server         : myproject
 5 Source Server Version : 50562
 6 Source Host           : localhost:3306
 7 Source Database       : mldn
 8 ​
 9 Target Server Type    : MYSQL
10 Target Server Version : 50562
11 File Encoding         : 65001
12 ​
13 Date: 2019-04-27 02:23:48
14 */
15 ​
16 SET FOREIGN_KEY_CHECKS=0;
17 ​
18 -- ----------------------------
19 -- Table structure for emp
20 -- ----------------------------
21 DROP TABLE IF EXISTS `emp`;
22 CREATE TABLE `emp` (
23   `empno` int(4) NOT NULL,
24   `ename` varchar(10) DEFAULT NULL,
25   `job` varchar(9) DEFAULT NULL,
26   `hiredate` date DEFAULT NULL,
27   `sal` float(7,2) DEFAULT NULL,
28   PRIMARY KEY (`empno`)
29 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
30 ​
31 -- ----------------------------
32 -- Records of emp
33 -- ----------------------------
34 INSERT INTO `emp` VALUES ('6060', '李兴华', '经理', '2001-09-16', '2000.30');
35 INSERT INTO `emp` VALUES ('7369', '董鸣楠', '销售', '2003-10-09', '1500.90');
36 INSERT INTO `emp` VALUES ('7698', '张惠', '销售', '2005-03-12', '800.00');
37 INSERT INTO `emp` VALUES ('7762', '刘明', '销售', '2005-03-09', '1000.00');
38 INSERT INTO `emp` VALUES ('7782', '杨军', '分析员', '2005-01-12', '2500.00');
39 INSERT INTO `emp` VALUES ('7839', '王月', '经理', '2006-09-01', '2500.00');
40 INSERT INTO `emp` VALUES ('8964', '李祺', '分析员', '2003-10-01', '3000.00');
    View Code

    将mysql的驱动"mysql-connector-java-5.1.47-bin.jar"复制到Tomcatlib 目录中，重启服务器

    使用JSP列出emp表数据

    驱动程序使用 com.mysql.jdbc.Driver

    list_emp.jsp

     1 <%@page import="org.apache.tomcat.dbcp.dbcp2.PStmtKey"%>
 2 <%@page import="com.sun.crypto.provider.RSACipher"%>
 3 <%@ page language="java" contentType="text/html; charset=UTF-8"
 4     pageEncoding="UTF-8"%>
 5 <%@ page import="java.sql.*" %>
 6 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 7 <html>
 8 <head>
 9 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
10 <title>Insert title here</title>
11 </head>
12 <body>
13 <%!
14     //定义数据库驱动程序
15     public static final String DBDRIVER = "com.mysql.jdbc.Driver";
16     //数据库连接地址
17     public static final String DBURL = "jdbc:mysql://localhost:3306/mldn";
18     public static final String DBUSER = "root";
19     public static final String DBPASS = "2580";
20 %>
21 <%
22     Connection conn = null;                 //声明数据库连接对象
23     PreparedStatement pstmt = null;         //声明数据库操作
24     ResultSet rs = null;                    //声明数据库结果集
25 %>
26 <%
27 try{                                        //数据库操作中会出现异常，所以要使用try...catch处理
28     Class.forName(DBDRIVER);                //数据库驱动程序加载
29     conn = DriverManager.getConnection(DBURL, DBUSER, DBPASS);//取得数据库连接
30     String sql = "SELECT empno,ename,job,sal,hiredate FROM emp";
31     pstmt = conn.prepareStatement(sql);     //实例化prepareStatement对象
32     rs = pstmt.executeQuery();              //执行查询操作
33 %>
34 <center>
35     <table border="1" width="80%">
36         <tr>                                <!-- 输出表格的行显示 -->
37             <td>雇员编号</td>                   <!-- 输出表格的行显示信息 -->
38             <td>雇员姓名</td>
39             <td>雇员工作</td>
40             <td>雇员工资</td>
41             <td>雇佣日期</td>
42         </tr>
43 <%
44     while(rs.next()){
45         int empno = rs.getInt(1);           //循环emp表中的行记录
46         String ename = rs.getString(2);     //取出雇员编号
47         String job = rs.getString(3);       //取出雇员姓名
48         float sal = rs.getFloat(4);         //取出雇员工作
49         java.util.Date date = rs.getDate(5);//取出雇佣日期
50 %>
51         <tr>                                <!-- 循环输出雇员的信息 -->
52             <td><%=empno %></td>
53             <td><%=ename %></td>
54             <td><%=job %></td>
55             <td><%=sal %></td>
56             <td><%=date %></td>
57         </tr>
58 <%
59         }
60 %>
61     </table>
62 </center>
63 <%
64 }catch(Exception e){                        //异常处理
65     System.out.println(e);                  //向Tomcat中打印
66 }finally{
67     rs.close();
68     pstmt.close();
69     conn.close();
70 }
71 %>
72 </body>
73 </html>
    View Code

    包含指令

    info.htm

    1 <h2>
2     <font color="red">info.htm</font>
3 </h2>
    View Code

    info.jsp

    1 <h2>
2     <font color="green"><%="info.jsp" %></font>
3 </h2>
    View Code

    info.inc

    1 <h2>
2     <font color="blue">info.inc</font>
3 </h2>
    View Code

    静态包含

    先包含，再处理

    include_demo01.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <h1>静态包含操作</h1>
11     <%@include file="info.htm" %>
12     <%@include file="info.jsp" %>
13     <%@include file="info.inc" %>
14 </body>
15 </html>
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    动态包含

    先处理，再包含

    include_demo02.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <h1>静态包含操作</h1>
11     <jsp:include page="info.htm"/>      <!-- 此处为标签指令，必须完结 -->
12     <jsp:include page="info.jsp"/>      <!-- 此处为标签指令，必须完结 -->
13     <jsp:include page="info.inc"/>      <!-- 此处为标签指令，必须完结 -->
14 </body>
15 </html>
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    使用request.getParameter()方法进行参数的传递

    receive_param.jsp

    1 <%@ page language="java" contentType="text/html; charset=UTF-8"
2     pageEncoding="UTF-8"%>
3 <h1>参数一：<%=request.getParameter("name") %></h1>
4 <h1>参数二：<%=request.getParameter("info") %></h1>
    View Code

    include_demo03.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 <%
11     String username="LiXinHua";     //定义一个变量
12 %>
13     <h1>动态包含并传递参数</h1>
14     <jsp:include page="receive_param.jsp">
15         <jsp:param value="<%=username %>" name="name"/>
16         <jsp:param value="www.mldnjava.cn" name="info"/>
17     </jsp:include>          <!-- 此处为标签完结指令，必须完结 -->
18 </body>
19 </html>
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    静态包含与动态包含的优劣之分

    静态包含处理页 include_demo04.jsp（错误的页面）

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 <%
11     int x = 100;
12 %>
13 <h1>include_demo04.jsp -- <%=x %></h1>
14 <%@include file="include.jsp" %>
15 <!-- 运行出现500错误，因为静态包含时，先将全部的内容包含到一起，然后再编译，导致了x的多次定义出错 -->
16 </body>
17 </html>
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    动态包含处理页 include_demo05.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 <%
11     int x = 100;
12 %>
13 <h1>include_demo05.jsp -- <%=x %></h1>
14 <jsp:include page="include.jsp"></jsp:include>
15 </body>
16 </html>
    View Code

    跳转指令

    服务器跳转，页面地址未发生改变

    不传递参数时

    1 <jsp:forword page="{要包含的文件路径|<%=表达式 %>}"/>
    View Code

    传递参数时（中间不能有空格）

    1 <jsp:forward>
2     <jsp:param name="参数名称" value="参数内容"/>
3 </jsp:forward>
    View Code

    forward_demo01.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 <%
11     String username = "LiXinHua";
12 %>
13 <jsp:forward page="forward_demo02.jsp">
14     <jsp:param value="<%=username %>" name="name"/>
15     <jsp:param value="www.MLDNJAVA.cn" name="info"/>
16 </jsp:forward>
17 </body>
18 </html>
    View Code

    forward_demo02.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 <h1>这是跳转之后的页面</h1>
11 <h2>参数一：<%=request.getParameter("name") %></h2>
12 <h2>参数二：<%=request.getParameter("info") %></h2>
13 </body>
14 </html>
    View Code

    实例操作：用户登录程序实现（JSP+JDBC实现）

    创建数据库表

     1 /*
 2 Navicat MySQL Data Transfer
 3 ​
 4 Source Server         : myproject
 5 Source Server Version : 50562
 6 Source Host           : localhost:3306
 7 Source Database       : mldn
 8 ​
 9 Target Server Type    : MYSQL
10 Target Server Version : 50562
11 File Encoding         : 65001
12 ​
13 Date: 2019-04-27 03:28:48
14 */
15 ​
16 SET FOREIGN_KEY_CHECKS=0;
17 ​
18 -- ----------------------------
19 -- Table structure for user
20 -- ----------------------------
21 DROP TABLE IF EXISTS `user`;
22 CREATE TABLE `user` (
23   `userid` varchar(30) NOT NULL,
24   `name` varchar(30) NOT NULL,
25   `password` varchar(32) NOT NULL,
26   PRIMARY KEY (`userid`)
27 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
28 ​
29 -- ----------------------------
30 -- Records of user
31 -- ----------------------------
32 INSERT INTO `user` VALUES ('admin', 'administrator', 'admin');
    View Code

    登录界面

    login.html

     1 <!DOCTYPE html>
 2 <html>
 3 <head>
 4 <meta charset="UTF-8">
 5 <title>请登录...</title>
 6 </head>
 7 <body>
 8 <center>
 9     <h1>登录操作</h1>
10     <hr>
11     <form action="login_check.jsp" method="post">
12         <table border="1">
13             <tr>
14                 <td colspan="2"><center>用户登录</center></td>
15             </tr>
16             <tr>
17                 <td>登录ID：</td>
18                 <td><input type="text" name="id"></td>
19             </tr>
20             <tr>
21                 <td>登录密码：</td>
22                 <td><input type="password" name="password"></td>
23             </tr>
24             <tr>
25                 <td colspan="2">
26                     <input type="submit" value="登录">
27                     <input type="reset" value="重置">
28                 </td>
29             </tr>
30         </table>
31     </form>
32     <hr>
33 </center>
34 </body>
35 </html>
    View Code

    校验界面

    login_check.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <%@ page import="java.sql.*" %>
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 8 <title>登录校验</title>
 9 </head>
10 <body>
11 <%!
12     //定义数据库驱动程序
13     public static final String DBDRIVER = "com.mysql.jdbc.Driver";
14     //数据库连接地址
15     public static final String DBURL = "jdbc:mysql://localhost:3306/mldn";
16     public static final String DBUSER = "root";
17     public static final String DBPASS = "2580";
18 %>
19 <%
20     Connection conn = null;                                 //声明数据库连接对象
21     PreparedStatement pstmt = null;                         //声明数据库操作
22     ResultSet rs = null;                                    //声明数据库结果集
23     boolean flag = false;                                   //标志位
24     String name = null;                                     //接收用户的真实姓名
25 %>
26 <%  //JDBC会抛出异常，使用try...catch处理
27 try{
28     Class.forName(DBDRIVER);                                //加载驱动程序
29     conn = DriverManager.getConnection(DBURL, DBUSER, DBPASS);//取得数据库连接
30     //编写要使用的SQL语句，验证用户id和密码，如果正确，则取出真实姓名
31     String sql = "SELECT name FROM user WHERE userid=? AND password=?";
32     pstmt = conn.prepareStatement(sql);                     //实例化prepareStatement对象
33     pstmt.setString(1, request.getParameter("id"));         //设置查询所需要的内容
34     pstmt.setString(2, request.getParameter("password"));   //设置查询所需要的内容
35     rs = pstmt.executeQuery();                              //执行查询操作
36     if(rs.next()){                                          //如果可以查询到，则表示合法用户
37         name = rs.getString(1);                             //取出真实姓名
38         flag = true;                                        //修改标志位，如果为true，表示登录成功
39     }
40 }catch(Exception e){
41     System.out.println(e);
42 }finally{
43     try{                                                    //关闭操作会抛出异常，使用try...catch处理
44         rs.close();                                         //关闭查询对象
45         pstmt.close();                                      //关闭操作对象
46         conn.close();                                       //关闭数据库连接
47     }catch(Exception e){}
48 }
49 %>
50 <%
51     if(flag){                                               //登录成功，跳转到成功页
52 %>
53             <%-- <jsp:forward page="login_success.jsp"> --%>            <!-- 执行跳转操作 -->
54             <%--    <jsp:param value="<%=name %>" name="uname"/> --%>
55             <%-- </jsp:forward> --%>
56 <%
57             response.setHeader("refresh", "3;URL=login_success.jsp");       //定时跳转
58             session.setAttribute("uname", name);
59 %>
60             <h3>用户如果登录成功，三秒后跳转到欢迎页！</h3>
61             <h3>如果没用跳转，请按<a href="login_success.jsp">这里</a></h3>
62 <%
63     }else{//登陆失败，跳转到失败页
64 %>
65 <jsp:forward page="login_failure.jsp"></jsp:forward><!-- 执行跳转操作 -->
66 <%
67     }
68 %>
69 </body>
70 </html>
    View Code

    登陆成功页面

    login_success.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>欢迎您，<%=session.getAttribute("uname")%></title>
 8 </head>
 9 <body>
10 <center>
11 <%
12     if(session.getAttribute("uname") != null){          //已经设置过属性，所以不为空
13 %>
14         <h1>登录操作</h1>
15         <hr>
16         <h2>登录成功</h2>
17         <h2>欢迎<%=session.getAttribute("uname")%>光临本系统，<a href="logout.jsp">注销</a>!</h2>
18 <%
19     }else{          //非法用户，没有登陆过，session中没有userid的存在
20 %>
21         <h3>请先进行系统的<a href="login.html">登录</a>!</h3>
22 <%
23     }
24 %>
25     
26     <%-- <h2>欢迎<font color="red"><%=request.getParameter("uname") %></font>光临！</h2> --%>
27 </center>
28 </body>
29 </html>
    View Code

    登录失败页面

    login_failure.jsp

     1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>登陆失败</title>
 8 </head>
 9 <body>
10 <center>
11     <h1>登录操作</h1>
12     <h2>登录失败，请重新<a href="login.html">登录</a></h2>
13 </center>
14 </body>
15 </html>
    View Code

    退出页面

    logout.jsp

     1 <%@ page language="java" contentType="text/html; charset=utf-8"
 2     pageEncoding="utf-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <title>已退出系统</title>
 7 </head>
 8 <body>
 9 ​
10 <h3>亲爱的<%=session.getAttribute("uname")%>，您已成功退出本系统，三秒后跳转回登录界面!</h3>
11 <h3>若果没有跳转，请按<a href="login.html">这里</a></h3>
12 ​
13 <%
14     response.setHeader("refresh", "3;URL=login.html");      //定时跳转
15     session.invalidate();                                   //注销，session清空
16 %>
17 ​
18 </body>
19 </html>
    View Code
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  • 原文地址：https://www.cnblogs.com/dream-by-dream/p/11699030.html
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