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

 
  
  
  
 
 
 
 

  
用户登录


  用户名：
   
密码：
   

   
         
   

  <>
 
 
  
 

2. 登录成功欢迎页面:login_success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>


 
 
 
 
 
 
 
 
 
 
 
 <%
  String userName = (String)session.getAttribute ( "UserName" );
 %>
 
  <%=userName%>
  欢迎您，登录成功！
 <>
 

3. 登录失败页面:login_failure.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>


 
 
 
 
 
 
 
 
 
 
 
 <%
 String userName = (String)session.getAttribute ( "UserName" );
 %>
 
  <%=userName%>
  对不起，登录失败！
 <>
 

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:

 
  LoginServlet
  LoginServlet
  zieckey.login.servlet.LoginServlet
 
 
  LoginServlet
  /LoginServlet
 

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