做了一个登录界面以下是代码：
login.jsp
- HTML code
<%@ page contentType="text/html; charset=gb2312"%><%request.setCharacterEncoding("gb2312");%><!-- 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=gb2312"> <meta http-equiv="Content-Language" content="ch-cn"> </head> <body bgcolor=cyan> <!-- 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="" size="20" maxlength="20" onfocus="if(this.value=='Your name')this.value=";"><br>密码： <input type="password" name="txtPassword" value="" size="20" maxlength="20" onfocus="if(this.value=='Your password')this.value=";"><br> <input type="submit" name="Submit" value="提交" onClick="validateLogin();" > <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>LoginServlet.java
- Java code
/** * 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;charset=GB2312" ); 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.jsp" ); } 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.jsp" ); } 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:3306/LearnJSP"; // 建立连接 java.sql.Connection connection = null; Statement stmt = null; ResultSet rs = null; try { connection = DriverManager.getConnection ( url, "root", "root" ); 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" ); request.getSession ( ).setAttribute ( "UserName", sUserName ); 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;}