MVC简单模式：登录

MVC简单模式：登录（转）

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>  <formmethod="post"name="frmLogin"action="LoginServlet"> <h1align="center">用户登录</h1><br> <divalign="center">用户名： <inputtype="text"name="txtUserName"value="Your name" size="20"maxlength="20" onfocus="if(this.value=='Your name')this.value='';"><br>密码： <inputtype="password"name="txtPassword"value="Your password" size="20"maxlength="20" onfocus="if(this.value=='Your password')this.value='';"><br> <inputtype="submit"name="Submit"　value="提交"onClick="validateLogin();">       <inputtype="reset"name="Reset"value="重置"><br> </div> </form>  <scriptlanguage="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"); %> <divalign=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; importjava.sql.Statement; importjava.io.IOException; importjava.sql.DriverManager; importjava.sql.ResultSet; importjava.sql.SQLException; importjavax.servlet.Servlet; importjavax.servlet.ServletException; importjavax.servlet.http.HttpServlet; importjavax.servlet.http.HttpServletRequest; importjavax.servlet.http.HttpServletResponse; publicclass 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 protectedvoid 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 protectedvoid doPost ( HttpServletRequest request, HttpServletResponse response ) throws ServletException,IOException { response.setContentType("text/html"); Stringresult=""; // 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 Stringurl="jdbc:mysql://localhost/LearnJSP"; // 建立连接 java.sql.Connectionconnection=null; Statement stmt =null; ResultSet rs =null; try { connection=DriverManager.getConnection(url,"root","011124"); stmt =connection.createStatement(); // SQL语句 Stringsql="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.

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