index.jsp(登录界面)
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>用户登录</title>
<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">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<style type="text/css">
</style>
</head>
<body>
<div>
<form action="loginServlet" method="post">
<table align="center" >
<tr>
<td>用户名:</td>
<td><input type="text" name="username"> <font color="red">
${requestScope.namemsg}${requestScope.nameError}</font></td>
</tr>
<tr>
<td>密码:</td>
<td><input type="password" name="password"> <font color="red">
${requestScope.pwdError}${requestScope.pwdmsg}</font></td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="登录">
<input type="reset" value="取消"></td>
</tr>
</table>
</form>
</div>
</body>
</html>
loginServlet(登录验证)
package com.dwx.servlet;
import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;
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 com.dwx.bean.user;
import com.dwx.bean.userDao;
/**
* 用户登录验证
*/
@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public loginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @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 {
String username=request.getParameter("username");
String password=request.getParameter("password");
//判断用户名、密码是否为空
if(username==""||username.length()==0){
request.setAttribute("namemsg","用户名为空!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
if(password==""||password.length()==0){
request.setAttribute("pwdmsg","密码为空!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
//判断用户名、密码是否正确
ResultSet rst=userDao.selectUser(username, password);
try {
if(rst.next()){
if(password.equals(rst.getString("password"))){
request.setAttribute("username",username);
request.getRequestDispatcher("items.jsp").forward(request, response);
}else{
request.setAttribute("pwdError","密码不正确!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
}else{
request.setAttribute("nameError","用户名不存在!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
userDao.java(查询用户)
package com.dwx.bean;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.dwx.util.dao;
public class userDao {
public static ResultSet selectUser(String username,String password){
Connection conn=dao.getConnection();
String sql="select * from user where username=?";
ResultSet rst=null;
try{
PreparedStatement prst=conn.prepareStatement(sql);
prst.setString(1, username);
rst=prst.executeQuery();
}catch(Exception ex){
ex.printStackTrace();
}
return rst;
}
}
dao.java(建立数据库连接)
package com.dwx.util;
import java.sql.Connection;
import java.sql.DriverManager;
public class dao {
public static Connection getConnection(){
Connection conn=null;
try{
Class.forName("com.mysql.jdbc.Driver"); //加载驱动
String url="jdbc:mysql://localhost:3306/db_item";
String username="root";
String password="root";
//创建数据库连接
conn=DriverManager.getConnection(url,username,password);
}catch(Exception ex){
ex.printStackTrace();
}
return conn;
}
}
效果演示：
1、用户名为空
2、密码为空
3、用户名不存在
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4、密码不正确
5、登录成功
