用JSP+Servlet+JavaBean模式实现一个简单的登录网页设计(JSP+Tomcat+MySQL)

                             By zieckey ( http://blog.csdn.net/zieckey)
                               All Rights Reserved!
 
这次涉及到四个文件:
登录页面:login.html
登录成功欢迎页面:login_success.jsp
登录失败页面:login_failure.jsp
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:
登录页面:login.html
 



<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 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>
 
    <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>

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">
  
 </head>
 <body>
  <%
   String userName = (String)session.getAttribute ( "UserName" );
  %>
  <div align=center>
   <%=userName%>
   欢迎您,登录成功!
  </div>
 </body>
</html>

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">
  
 </head>
 <body>
  <%
  String userName = (String)session.getAttribute ( "UserName" );
  %>
  <div align=center>
   <%=userName%>
   对不起,登录失败!
  </div>
 </body>
</html>

 

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              META-INF
007-01-18  15:16              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              classes
007-01-18  15:16              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.
 

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