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();

}

}

}

login.jsp 内容

pageEncoding="UTF-8"%>

用户登录

用户登录

用户名：
密  码

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 ;

}

}

success.jsp 内容

pageEncoding="UTF-8"%>

Insert title here

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" ;

}

%>

fail.jsp 内容

pageEncoding="UTF-8"%>

Insert title here

String userName = (String) session.getAttribute("username");

String msg = (String) session.getAttribute("message");

%>

response.setHeader("Refresh", "5;URL=/webDemo/login.jsp");

%>

-------------------------------------------------------配置数据库------------------------------------------------------

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

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">

webDemo

index.html

index.htm

index.jsp

default.html

default.htm

default.jsp

LoginTestServlet

com.test.LoginTestServlet

LoginTestServlet

/loginTestServlet