servlet+jdbc+jsp实现登录界面的验证（基于MVC思想）
一、MVC的概念
MVC是模型(Model)和视图(View)以及控制器(Controller)的简写，是一种将数据、界面显示和业务 逻辑进行分离的组织方式，这样在改进界面及用户交互时，不需要重新编写业务逻辑，从而提高了 代码的可维护性。
- M：主要用于封装业务数据的JavaBean(Bean) 和 业务逻辑的JavaBean(Service)及访问数据库的
DAO对象。
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V：主要负责数据收集 和 数据展现，通常由JSP文件完成。
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C：主要负责流程控制 和 页面跳转，通常由Servlet完成。
原始的登录验证方法：
改进的登录验证方法：
这样实现了解耦，从而具备了更好的扩展性。
二、需求
- 浏览器 进入 登录界面，输入用户名、密码，发送到服务器。
- 服务器完成数据库查询和验证，返回验证结果。
- 验证结果呈现在响应界面上。
三、代码演示
1、编写登录界面
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创建空工程，在工程中创建javaEE模块
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配置中设置tomcat的部署
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编写login界面
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %> DOCTYPE html> <html> <head> <title>JSP - logintitle> head> <body> <form action="loginServlet" method="post"> 用户名：<input type="text" name="userName"><br> 密 码：<input type="text" name="password"><br> <input type="submit" value="登录"> form> body>
2、编写LoginServlet实现获取用户名和密码
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编写servlet
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LoginServlet
package com.example.login_demo.servlet; import com.example.login_demo.pojo.User; import com.example.login_demo.service.UserService; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.annotation.*; import java.io.IOException; @WebServlet(name = "LoginServlet", value = "/loginServlet") public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1、获取的用户名和密码 String userName = request.getParameter("userName"); System.out.println("获取的用户名：" + userName); String password = request.getParameter("password"); System.out.println("获取的密码：" + password); } }
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单元测试：
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运行tomcat
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访问登录界面，发送登录请求
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3、操作数据库部分
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数据准备，db_web数据库下准备t_user表
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编写DbUtils，实现jdbc的封装
package com.example.login_demo.utils; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.SQLException; public class DbUtils { private static String jdbcName; private static String dbUrl; private static String dbUserName; private static String dbPassword; static { jdbcName = "com.mysql.jdbc.Driver"; dbUrl = "jdbc:mysql://localhost:3306/db_web?useSSL=false"; dbUserName = "root"; dbPassword = "root"; try { Class.forName(jdbcName); } catch (ClassNotFoundException e) { e.printStackTrace(); } } public static Connection getConnection() throws SQLException { Connection connection = DriverManager.getConnection(dbUrl, dbUserName, dbPassword); return connection; } public static void closeResource(Connection connection, PreparedStatement preparedStatement) throws SQLException { if (null != connection){ connection.close(); } if (null != preparedStatement){ preparedStatement.close(); } } } -
原始数据类型User
package com.example.login_demo.pojo; public class User { private int id; private String userName; private String password; public User(String userName, String password) { this.userName = userName; this.password = password; } public int getId() { return id; } public void setId(int id) { this.id = id; } 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; } @Override public String toString() { return "User{" + "id=" + id + ", userName='" + userName + '\'' + ", password='" + password + '\'' + '}'; } } -
dao层直接操作数据库
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UserDao接口
package com.example.login_demo.dao; import com.example.login_demo.pojo.User; public interface UserDao { //查询用户 User userLogin(User user); } -
UserDaoImpl接口实现类
package com.example.login_demo.dao; import com.example.login_demo.pojo.User; import com.example.login_demo.utils.DbUtils; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; public class UserDaoImpl implements UserDao { @Override public User userLogin(User user) { Connection connection = null; PreparedStatement preparedStatement = null; ResultSet resultSet = null; try { //1、获取数据库连接 connection = DbUtils.getConnection(); //2、准备sql语句 String sql = "select * from t_user where userName = ? and password = ?"; //3、执行sql返回结果 preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1, user.getUserName()); preparedStatement.setString(2, user.getPassword()); resultSet = preparedStatement.executeQuery(); if (resultSet.next()){ User returnUser = new User(resultSet.getString("userName"), resultSet.getString("password")); returnUser.setId(Integer.parseInt(resultSet.getString("id"))); return returnUser; //查找成功 } }catch (SQLException e){ e.printStackTrace(); }finally { //4、释放资源 try { DbUtils.closeResource(connection, preparedStatement); if (null != resultSet){ resultSet.close(); } } catch (SQLException e) { e.printStackTrace(); } } return null;//查找失败 } public static void main(String[] args) { UserDao userDao = new UserDaoImpl(); User admin = userDao.userLogin(new User("admin", "12345")); System.out.println("查找到的用户：" + admin); } }
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单元测试：
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执行UserDaoImpl中的测试代码
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4、service层实现
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UserDaoFactory实现：简单的静态工厂实现UserDao的实例创建，实现创建和使用的解耦
package com.example.login_demo.factory; import com.example.login_demo.dao.UserDao; import com.example.login_demo.dao.UserDaoImpl; public class UserDaoFactory { public static UserDao getUserDao(){ return new UserDaoImpl(); } } -
service层实现dao层调用
package com.example.login_demo.service; import com.example.login_demo.dao.UserDao; import com.example.login_demo.factory.UserDaoFactory; import com.example.login_demo.pojo.User; public class UserService { private UserDao userDao; public UserService(){ this.userDao = UserDaoFactory.getUserDao(); } public User userLoginService(User user){ return userDao.userLogin(user); } }
5、修改Servlet，实现数据库的查找验证
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LoginServlet
package com.example.login_demo.servlet; import com.example.login_demo.pojo.User; import com.example.login_demo.service.UserService; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.annotation.*; import java.io.IOException; @WebServlet(name = "LoginServlet", value = "/loginServlet") public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1、获取的用户名和密码 String userName = request.getParameter("userName"); System.out.println("获取的用户名：" + userName); String password = request.getParameter("password"); System.out.println("获取的密码：" + password); //2、创建UserService类型的对象实现数据的校验功能 UserService userService = new UserService(); User user = userService.userLoginService(new User(userName, password)); if (null != user){ System.out.println("登录成功！"); }else { System.out.println("登录失败！"); } } } -
单元测试：
6、修改Servlet，实现页面的跳转
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修改LoginServlet，当成功时，跳转到成功界面；当失败时，跳转回登录界面并显示账号或者密码错误
package com.example.login_demo.servlet; import com.example.login_demo.pojo.User; import com.example.login_demo.service.UserService; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.annotation.*; import java.io.IOException; @WebServlet(name = "LoginServlet", value = "/loginServlet") public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1、获取的用户名和密码 String userName = request.getParameter("userName"); System.out.println("获取的用户名：" + userName); String password = request.getParameter("password"); System.out.println("获取的密码：" + password); //2、创建UserService类型的对象实现数据的校验功能 UserService userService = new UserService(); User user = userService.userLoginService(new User(userName, password)); if (null != user){ System.out.println("登录成功！"); //登录成功的信息放入session对象实现多个请求共享 request.getSession().setAttribute("user", user); //实现客户端跳转 response.sendRedirect("main.jsp"); }else { System.out.println("登录失败，用户名或者密码错误！"); request.setAttribute("error", "登录失败，用户名或者密码错误！"); //实现服务器跳转，使用转发，共享request RequestDispatcher requestDispatcher = request.getRequestDispatcher("login.jsp"); requestDispatcher.forward(request, response); } } } -
main.jsp
<%@ page import="com.example.login_demo.pojo.User" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
主页面
登录成功！欢迎 <%=(User)session.getAttribute("user")%> !
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login.jsp
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>JSP - login -
测试：
