Servlet——用户登录案例

案例：用户登录

* 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

* 分析

* 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cn.itcast.domain,创建类User
		package cn.itcast.domain;
		/**
		 * 用户的实体类
		 */
		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
		package cn.itcast.util;

		import com.alibaba.druid.pool.DruidDataSourceFactory;

		import javax.sql.DataSource;
		import javax.xml.crypto.Data;
		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cn.itcast.dao,创建类UserDao,提供login方法

		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>(User.class),
		                    loginUser.getUsername(), loginUser.getPassword());

​

		            return user;
		        } catch (DataAccessException e) {
		            e.printStackTrace();//记录日志
		            return null;
		        }
		    }
		}

	6. 编写cn.itcast.web.servlet.LoginServlet类
		package cn.itcast.web.servlet;

		import cn.itcast.dao.UserDao;
		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("/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
		@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");
		        }

​

		    }

		@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);
		    }
		}

	8. login.html中form表单的action路径的写法
		* 虚拟目录+Servlet的资源路径

	9. BeanUtils工具类，简化数据封装
		* 用于封装JavaBean的
		1. JavaBean：标准的Java类
			1. 要求：
				1. 类必须被public修饰
				2. 必须提供空参的构造器
				3. 成员变量必须使用private修饰
				4. 提供公共setter和getter方法
			2. 功能：封装数据

		2. 概念：
			成员变量：
			属性：setter和getter方法截取后的产物
				例如：getUsername() --> Username--> username

		3. 方法：
			1. setProperty() //与settergetter方法保持一致
			2. getProperty()
			3. populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中

GitHub:https://github.com/PoetryAndYou/LoginCase