JavaWeb登陆功能实现代码

<form action="LoginServlet" method="post">
  用户名:<input type="text" name="userName"/>
  密码：<input type="password" name="password"/>
  <input type="submit" value="提交"/>
 </form>

public class User {
 private String userName;
 private String password;
 public String getUserName() {
 return userName;
 }
 public void setUserName(String userName) {
 this.userName = userName;
 }
 public String getPassword() {
 return password;
 }
 public void setPassword(String password) {
 this.password = password;
 }
}

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.test.dao.UserDao;
//创建时为Servlet而不是Class，需要在web.xml中进行配置，配置的代码Myeclipse将自动生成
public class LoginServlet extends HttpServlet {
 //创建UserDao的对象，以便于查询数据库
 UserDao userDao=new UserDao();
 //以下doGet方法和doPost方法分别对应form表单中的method="get"和method="post"
 public void doGet(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {
 }
 public void doPost(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {
 //利用getParameter方法获取到前台文本框中输入的值，其中括号内的内容为<input/>标签中的name属性
 String userName=request.getParameter("userName");
 String password=request.getParameter("password");
 //调用UserDao中的getSelect方法并获取到返回值
 boolean flag=userDao.getSelect(userName, password);
 //若用户名和密码存在则转发到index.jsp页面，否则重定向到error.jsp页面
 if (flag) {
  request.getRequestDispatcher("index.jsp").forward(request, response);
 }
 else
  response.sendRedirect("error.jsp");
 }

}

package com.test.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class UserDao {
 //连接数据库的代码
 public Connection getCon() {
 //数据库连接名称
 String username="root";
 //数据库连接密码
 String password="";
 String driver="com.mysql.jdbc.Driver";
 //其中test为数据库名称
 String url="jdbc:mysql://localhost:3306/test";
 Connection conn=null;
 try{
  Class.forName(driver);
  conn=(Connection) DriverManager.getConnection(url,username,password);
 }catch(Exception e){
  e.printStackTrace();
 }
 return conn;
 }
 //进行查询的方法，若含有满足条件的数据则返回true
 public boolean getSelect(String userName,String password) { 
 boolean flag=false;
  String sql = "select * from user where userName='"+userName+"' and password='"+password+"'"; 
  Connection conn = getCon();
  PreparedStatement pst = null;
  try {
  pst = (PreparedStatement) conn.prepareStatement(sql);
  ResultSet rs = pst.executeQuery();
  if (rs.next()) {
   flag=true;
  }
  } catch (Exception e) {
  }
  return flag;
 }
}

<?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">
 <servlet>
 <servlet-name>LoginServlet</servlet-name>
 <servlet-class>com.test.servlet.LoginServlet</servlet-class>
 </servlet>

 <servlet-mapping>
 <servlet-name>LoginServlet</servlet-name>
 <url-pattern>/LoginServlet</url-pattern>
 </servlet-mapping>
</web-app>