涉及以下几个文件：
1。登录页面 login.jsp
2，成功跳转页面 success.jsp
3，失败跳转页面 fail.jsp
4，servlet 处理类 LoginTestServlet.java
5，配置文件 web.xml
--------------------------------------------- 依次看代码 --------------------------------------------
LoginTestServlet.java 内容
package com.test;
import java.io.IOException;
import java.sql.DriverManager;
import java.sql.ResultSet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
/**
* Servlet implementation class LoginTestServlet
*/
@WebServlet("/LoginTestServlet")
public class LoginTestServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginTestServlet() {
super();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/heml;charset=gb2312");
request.setCharacterEncoding("gb2312");
String result = "";
String username = request.getParameter("username");
String psw = request.getParameter("password");
if(username == "" || username == null || username.length()>20){
try {
result = "请输入用户名（不能超过20个字符）";
request.setAttribute("message", result);
response.sendRedirect("login.jsp");
return;
} catch (Exception e) {
e.printStackTrace();
}
}
if(psw == "" || psw == null || psw.length() > 20){
try {
result = "请输入password（不能超过20个字符）";
request.setAttribute("message", result);
response.sendRedirect("login.jsp");
return;
} catch (Exception e) {
e.printStackTrace();
}
}
//登记JDBC驱动程序
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (Exception e) {
System.out.print("Class Not Found Exception");
}
//链接URL
String url = "jdbc:mysql://localhost:3306/demo";
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
conn = (Connection) DriverManager.getConnection(url,"root","root");
stmt = (Statement) conn.createStatement();
String sql = "select * from userInfo where username='"+username+"' and userpsw= '"+psw+"'";
rs = stmt.executeQuery(sql);
} catch (Exception e) {
e.printStackTrace();
}
HttpSession session = request.getSession();
session.setAttribute("username", username);
try {
if(rs.next()){
session.setAttribute("age",rs.getString("age")) ;
session.setAttribute("sex",rs.getString("sex")) ;
session.setAttribute("weight",rs.getString("weight")) ;
response.sendRedirect("success.jsp") ;
return;
}else{
session.setAttribute("message", "用户名或password不匹配。");
response.sendRedirect("fail.jsp") ;
return;
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户登录</title>
</head>
<body>
<form method="POST" name="frmLogin" action="LoginTestServlet">
<h1 align="center">用户登录</h1>
<center>
<table border="1">
<tr>
<td>用户名：</td>
<td>
<input type="text" name="username" value="" size="20" maxlength="20" onfocus="if (this.value=='Your name') this.value='';" />
</td>
</tr>
<tr>
<td>密 码</td>
<td>
<input type="password" name="password" value="" size="20" maxlength="20" onfocus="if(this.value=='Your Password') this.value='';">
</td>
</tr>
<tr>
<td>
<input type="submit" name="Submit" value=" 提交" onclick="return validateLogin()">
</td>
<td>
<input type="reset" name="Reset" value="重置" />
</td>
</tr>
</table>
</center>
</form>
<script type="text/javascript">
function validateLogin(){
var sUserName = document.frmLogin.username.value;
var sPassword = document.frmLogin.psssword.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>success.jsp 内容
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String userName = (String)session.getAttribute("username") ;
String age = (String)session.getAttribute("age") ;
String weight = (String)session.getAttribute("weight") ;
String sex = (String)session.getAttribute("sex") ;
System.out.println("性别：A" + sex +"A") ;
if (sex.trim().equals("M")) {
sex ="男" ;
}else{
sex = "女" ;
}
%>
<div align="center">
<%=userName %>
欢迎您，登陆成功。<br />
<font color="blue">登陆用户信息：</font>
<table border =1 >
<tr>
<td> 姓名： </td>
<td> <%=userName %> </td>
</tr>
<tr>
<td> 年龄： </td>
<td> <%=age %> </td>
</tr>
<tr>
<td> 体重： </td>
<td> <%=weight %> kg </td>
</tr>
<tr>
<td> 性别： </td>
<td> <%=sex %> </td>
</tr>
</table>
<a href="login.jsp">返回</a>
</div>
</body>
</html>fail.jsp 内容
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String userName = (String) session.getAttribute("username");
String msg = (String) session.getAttribute("message");
%>
<div align="center">
<%=userName%>
对不起。登陆失败！<br /> <font color="red">原因： </font>
<%=msg%>
<br /> <br /> 5秒后将返回登陆界面。
</div>
<%
response.setHeader("Refresh", "5;URL=/webDemo/login.jsp");
%>
</body>
</html>
mysql数据库中须要创建数据库demo，当中创建表userInfo 创建表语句为：
create databasedemo;
use demo
create table userInfo(id int not null primary key,username char(20) not null,userpsw char(20) ,age int ,weight int ,sex enum('M','F')) ;
须要把连接mysql的jar包放到项目的lib文件夹中
---------------------------------------------华丽的切割线----------------------------------------
最后 web.xml 内容
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>webDemo</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list>
<servlet> <servlet-name>LoginTestServlet</servlet-name> <servlet-class>com.test.LoginTestServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginTestServlet</servlet-name> <url-pattern>/loginTestServlet</url-pattern> </servlet-mapping> </web-app>