JSP+Servlet+JavaBean实现登录网页实例详解

袁宜民

2023-03-14

本文向大家介绍JSP+Servlet+JavaBean实现登录网页实例详解，包括了JSP+Servlet+JavaBean实现登录网页实例详解的使用技巧和注意事项，需要的朋友参考一下

本文实例讲述了JSP+Servlet+JavaBean实现登录网页的方法。分享给大家供大家参考。具体如下：

这里涉及到四个文件:

1. 登录页面:login.html
2. 登录成功欢迎页面:login_success.jsp
3. 登录失败页面:login_failure.jsp
4. Servlet处理文件:LoginServlet.java

其实还涉及到一个文件:web.xml,这个后面再说:

下面分别介绍这几个文件:

1. 登录页面:login.html

<!-- 该Login页面是一个简单的登录界面 -->
<!--
 该JSP程序是用来测试与MySQL数据库的连接，
 需要一个数据库：LearnJSP，和其中一个表：userinfo
 表中有两个字段分别为：UserName varchar (20) not null,UserPwd varchar (20) not null
-->
<html>
 <head>
  <title>登录</title>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <meta http-equiv="Content-Language" content="ch-cn">
 </head>
 <body>
 <!-- Form 用来提取用户填入并提交的信息-->
 <form method="post" name="frmLogin" action="LoginServlet">
  <h1 align="center">用户登录</h1><br>
  <div align="center">用户名：
   <input type="text" name="txtUserName" value="Your name"
    size="20" maxlength="20"
    onfocus="if(this.value=='Your name')this.value='';"><br>密码：
   <input type="password" name="txtPassword" value="Your password"
    size="20" maxlength="20"
    onfocus="if(this.value=='Your password')this.value='';"><br>
   <input type="submit" name="Submit"　value="提交" onClick="validateLogin();" >
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
   <input type="reset" name="Reset" value="重置"><br>
  </div>
 </form>
 <!-- javaScript 函数 validateLogin(),用来验证用户名和密码是否为空 -->
  <script language="javaScript">
   function validateLogin()
   {
   var sUserName = document.frmLogin.txtUserName.value;
   var sPassword = document.frmLogin.txtPassword.value;
   if( sUserName=="" )
   {
    alert("请输入用户名！");
    return false;
   }
   if( sPassword=="" )
   {
    alert("请输入密码！");
    return false;
   }
   }
  </script>
 </body>
</html>

2. 登录成功欢迎页面:login_success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <title>My JSP 'login_failure.jsp' starting page</title>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 <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>
 <%
  String userName = (String)session.getAttribute ( "UserName" );
 %>
 <div align=center>
  <%=userName%>
  欢迎您，登录成功！
 </div>
 </body>
</html>

3. 登录失败页面:login_failure.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <title>My JSP 'login_failure.jsp' starting page</title>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 <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>
 <%
 String userName = (String)session.getAttribute ( "UserName" );
 %>
 <div align=center>
  <%=userName%>
  对不起，登录失败！
 </div>
 </body>
</html>

4. Servlet处理文件:LoginServlet.java

/**
 * 该JSP程序是用来测试与MySQL数据库的连接，
 * 需要一个数据库：LearnJSP，和其中一个表：userinfo
 * 表中有两个字段分别为：UserName varchar (20) not null,UserPwd varchar (20) not null
 */
package zieckey.login.servlet;
import java.sql.Statement;
import java.io.IOException;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet implements Servlet
{
 public LoginServlet ()
 {
 // TODO Auto-generated constructor stub
 }
 /*
 * (non-Javadoc)
 *
 * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest,
 * javax.servlet.http.HttpServletResponse)
 */
 @Override
 protected void doGet ( HttpServletRequest arg0, HttpServletResponse arg1 )
  throws ServletException, IOException
 {
 }
 /*
 * (non-Javadoc)
 *
 * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest,
 * javax.servlet.http.HttpServletResponse)
 */
 @Override
 protected void doPost ( HttpServletRequest request, HttpServletResponse response )
  throws ServletException, IOException
 {
 response.setContentType ( "text/html" );
 String result = "";
 // 获取用户名
 String sUserName = request.getParameter ( "txtUserName" );
 if ( sUserName == "" || sUserName == null || sUserName.length ( ) > 20 )
 {
  try
  {
  result = "请输入用户名（不超过20字符）！";
  request.setAttribute ( "ErrorUserName", result );
  response.sendRedirect ( "login.html" );
  } catch ( Exception e )
  {
  }
 }
 // 获取密码
 String sPasswd = request.getParameter ( "txtPassword" );
 if ( sPasswd == "" || sPasswd == null || sPasswd.length ( ) > 20 )
 {
  try
  {
  result = "请输入密码（不超过20字符）！";
  request.setAttribute ( "ErrorPassword", result );
  response.sendRedirect ( "login.html" );
  } catch ( Exception e )
  {
  }
 }
 // 登记JDBC驱动程序
 try
 {
  Class.forName ( "org.gjt.mm.mysql.Driver" ).newInstance ( );
 } catch ( InstantiationException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
  System.out.println ("InstantiationException");
 } catch ( IllegalAccessException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
  System.out.println ("IllegalAccessException");
 } catch ( ClassNotFoundException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
  System.out.println ("ClassNotFoundException");
 }
 // 连接参数与Access不同
 String url = "jdbc:mysql://localhost/LearnJSP";
 // 建立连接
 java.sql.Connection connection = null;
 Statement stmt = null;
 ResultSet rs = null;
 try
 {
  connection = DriverManager.getConnection ( url, "root", "011124" );
  stmt = connection.createStatement ( );
  // SQL语句
  String sql = "select * from userinfo where username='" + sUserName
   + "' and userpwd = '" + sPasswd + "'";
  rs = stmt.executeQuery ( sql );// 返回查询结果
 } catch ( SQLException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
 }
 try
 {
  if ( rs.next ( ) )// 如果记录集非空，表明有匹配的用户名和密码，登陆成功
  {
  // 登录成功后将sUserName设置为session变量的UserName
  // 这样在后面就可以通过 session.getAttribute("UserName") 来获取用户名，
  // 同时这样还可以作为用户登录与否的判断依据
  request.getSession ( ).setAttribute ( "UserName", sUserName );
  response.sendRedirect ( "login_success.jsp" );
  } else
  {
  // 否则登录失败
  //response.sendRedirect ( "MyJsp.jsp" );
  response.sendRedirect ( "login_failure.jsp" );
  }
 } catch ( SQLException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
 }
 try
 {
  if ( null!=rs )
  {
  rs.close ( );
  }
  if ( null!=stmt )
  {
  stmt.close ( );
  }
  if ( null!=connection )
  {
  connection.close ( );
  }
 } catch ( SQLException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
 }
 }
 /**
 *
 */
 private static final long serialVersionUID = 1L;
}

为了让这个网站正常运行还要到web.xml中注册一下,
现该文件内容修改如下:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.4" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 <servlet>
  <display-name>LoginServlet</display-name>
  <servlet-name>LoginServlet</servlet-name>
  <servlet-class>zieckey.login.servlet.LoginServlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>LoginServlet</servlet-name>
  <url-pattern>/LoginServlet</url-pattern>
 </servlet-mapping>
</web-app>

好了,这几个文件就可以构成我们的这个登录界面了.

注意事项:

1. 文件目录形式

login.html,login_success.html,login_failure.html这三个文件放在同一目录,
LoginServlet.java该文件的字节码文件LoginServlet.class放在WEB-INF/classes目录下(注意jar包顺序)
现在整个工程的目录形式是:
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login 的目录
007-01-18 15:16    <DIR>          META-INF
007-01-18 15:16    <DIR>          WEB-INF
007-01-18 16:17             1,801 login.html
007-01-18 15:48               858 login_failure.jsp
007-01-18 15:40               234 login_success.html
007-01-18 15:46               781 MyJsp.jsp
007-01-18 16:12               859 login_success.jsp
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login/WEB-INF 的目录
007-01-18 15:16    <DIR>          classes
007-01-18 15:16    <DIR>          lib
007-01-18 16:21               606 web.xml
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login/WEB-INF/classes/zieckey/login/servlet 的目录
2007-01-18 16:18             3,900 LoginServlet.class

2. 其他注意事项

数据库MySQL服务器程序要先启动起来.

希望本文所述对大家的JSP程序设计有所帮助。

JSP+Servlet+JavaBean实现登录网页实例详解

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