实现用户登录案例

需求

    1.编写login.html登录页面
    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

开发步骤

        1. 创建项目，导入html页面，配置文件，jar包

        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);

        3.创建包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util,编写工具类JDBCUtils

import com.alibaba.druid.pool.DruidDataSourceFactory;import javax.sql.DataSource;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.SQLException;import java.util.Properties;/** * JDBC工具类，使用Durid连接池 */public class JDBCUtils {    private static DataSource ds;    static { try {     //1.加载配置文件     Properties pro = new Properties();     //使用ClassLoader加载配置文件，获取字节输入流     InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");     pro.load(is);     //2.初始化连接池对象     ds = DruidDataSourceFactory.createDataSource(pro); } catch (IOException e) {     e.printStackTrace(); } catch (Exception e) {     e.printStackTrace(); }    }    /**     * 获取连接池对象     */    public static DataSource getDataSource(){ return ds;    }    /**     * 获取连接Connection对象     */    public static Connection  getConnection() throws SQLException { return ds.getConnection();    }}

         5. 创建包dao,创建类UserDao,提供login方法

import domin.User;import 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 loginUsr 只有用户名跟密码     * @return  user包含用户所有数据，没有查询到，返回null     */    public User login(User loginUsr){ 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),      loginUsr.getUsername(), loginUsr.getPassword());     return user; } catch (DataAccessException e) {     e.printStackTrace();//记录日志     return null; }    }}

        6. 编写web.servlet.LoginServlet类

import dao.UserDao;import domin.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);  //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);    }}

        7. 编写FailServlet和SuccessServlet类

import domin.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()+",欢迎你！"); }    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response);    }}

package 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，用户名或者密码错误");    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response);    }}