jsp+servlet登陆实例演示

最新推荐文章于 2024-06-10 08:00:00 发布

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最新推荐文章于 2024-06-10 08:00:00 发布

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分类专栏：编程案例分享文章标签： servlet 实例案例

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本文介绍了一个基于HTML、Java Servlet和MySQL的简易登录系统的实现过程，包括登录页面、处理Servlet及数据库交互等内容。

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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();" >       <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

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.