JavaEE入门小项目：使用数据库完成登陆功能

2024-06-12 20:37| 来源: 网络整理| 查看: 265

通过本例来巩固下所学的Java Web知识（Servlet、数据库、html）

用户登录案例需求： 1.编写login.html登录页面 username & password 两个输入框 2.使用Druid数据库连接池技术,操作mysql，day14数据库中user表 3.使用JdbcTemplate技术封装JDBC 4.登录成功跳转到SuccessServlet展示：登录成功！用户名,欢迎您 5.登录失败跳转到FailServlet展示：登录失败，用户名或密码错误在这里插入图片描述

1.创建项目，导入html页面，配置文件，jar包创建JavaEE项目：http端口号80，虚拟目录名为day14_test 在这里插入图片描述配置文件druid.properties配置数据库连接池：

driverClassName=com.mysql.jdbc.Driver url=jdbc:mysql:///day14 灰色斜杠被转义了，其实是三个斜杠 username=root password=root initialSize=5 maxActive=10 maxWait=3000

然后导入项目需要的jar包：把lib添加到library 在这里插入图片描述书写前端代码：

Title 用户名: 密码:

前端页面效果：在这里插入图片描述 2、创建数据库环境

CREATE DATABASE day14; USE day14; CREATE TABLE USER( id INT PRIMARY KEY AUTO_INCREMENT, username VARCHAR(32) UNIQUE NOT NULL, PASSWORD VARCHAR(32) NOT NULL ); // 可以在其中插入一些数据 INSERT INTO USER VALUES(2,"zhangsan","123");

3.创建包cn.itcast.domain,创建类User

public class User { private int id; private String username; private String 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 + '\'' + '}'; } }

4.创建包cn.itcast.util,编写工具类JDBCUtils,简化数据库连接池的操作

package cn.itcast.util; import com.alibaba.druid.pool.DruidDataSourceFactory; import javax.sql.DataSource; import java.io.IOException; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Properties; public class JDBCUtils { private static DataSource ds; static{ Properties pro = new Properties(); try { pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties")); ds= DruidDataSourceFactory.createDataSource(pro); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } public static void close(Statement stmt, Connection conn, ResultSet rs){ if(stmt!=null){ try { stmt.close(); } catch (SQLException throwables) { throwables.printStackTrace(); } } if(conn!=null){ try { conn.close(); } catch (SQLException throwables) { throwables.printStackTrace(); } } if(rs!=null){ try { rs.close(); } catch (SQLException throwables) { throwables.printStackTrace(); } } } public static void close(Statement stmt, Connection conn){ close(stmt,conn,null); } public static DataSource getDataSource(){ return ds; } }

5.创建包cn.itcast.dao,创建类UserDao,提供login方法,使用JDBCTemplate

package cn.itcast.dao; import cn.itcast.domain.User; import cn.itcast.util.JDBCUtils; import org.springframework.dao.DataAccessException; import org.springframework.jdbc.core.BeanPropertyRowMapper; import org.springframework.jdbc.core.JdbcTemplate; /** * 操作数据库中User表的类 */ public class UserDao { //声明JDBCTemplate对象共用 private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource()); /** * 登录方法 * @param loginUser 只有用户名和密码 * @return user包含用户全部数据,没有查询到，返回null */ public User login(User loginUser){ try { //1.编写sql String sql = "select * from user where username = ? and password = ?"; //2.调用query方法 User user = template.queryForObject(sql, new BeanPropertyRowMapper(User.class), loginUser.getUsername(), loginUser.getPassword()); return user; } catch (DataAccessException e) { e.printStackTrace();//记录日志 return null; } } }

6.书写三个servlet一个用于登录判断，另外两个作为跳转页面：用来判断登录的servlet：BeanUtils是封装JavaBean的工具，能把Map集合直接封装为JavaBean，使用populate方法封装。

package cn.itcast.web.servlet; import cn.itcast.dao.UserDao; import cn.itcast.domain.User; import org.apache.commons.beanutils.BeanUtils; 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 java.io.IOException; import java.lang.reflect.InvocationTargetException; import java.util.Map; @WebServlet("/loginServlet") public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.设置编码 req.setCharacterEncoding("utf-8"); /* //2.获取请求参数 String username = req.getParameter("username"); String password = req.getParameter("password"); //3.封装user对象 User loginUser = new User(); loginUser.setUsername(username); loginUser.setPassword(password);*/ //2.获取所有请求参数 Map map = req.getParameterMap(); //3.创建User对象 User loginUser = new User(); //3.2使用BeanUtils封装 try { BeanUtils.populate(loginUser,map); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } //4.调用UserDao的login方法 UserDao dao = new UserDao(); User user = dao.login(loginUser); //5.判断user if(user == null){ //登录失败 req.getRequestDispatcher("/failServlet").forward(req,resp); }else{ //登录成功 //存储数据 req.setAttribute("user",user); //转发 req.getRequestDispatcher("/successServlet").forward(req,resp); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req,resp); } }

登录成功servlet：

package cn.itcast.web.servlet; import cn.itcast.domain.User; 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 java.io.IOException; @WebServlet("/successServlet") public class SuccessServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取request域中共享的user对象 User user = (User) request.getAttribute("user"); if(user != null){ //给页面写一句话 //设置编码 response.setContentType("text/html;charset=utf-8"); //输出 response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您"); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

登录失败servlet：

package cn.itcast.web.servlet; 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 java.io.IOException; @WebServlet("/failServlet") public class FailServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //给页面写一句话 //设置编码 response.setContentType("text/html;charset=utf-8"); //输出 response.getWriter().write("登录失败，用户名或密码错误"); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

最后启动项目，在浏览器访问localhost/day14_test/login.html进行登录即可，若出现意料以外的小问题，试试清空浏览器的缓存。跳转成功！在这里插入图片描述

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