简单的用户登录案例

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，oyqj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 oyqj;
		USE oyqj;
		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.oyqj.domain,创建类User
		package cn.oyqj.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.oyqj.util,编写工具类JDBCUtils
		package cn.oyqj.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.oyqj.dao,创建类UserDao,提供login方法

package cn.oyqj.dao;

import cn.oyqj.domain.User;
import cn.oyqj.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.oyqj.web.servlet.LoginServlet类
package cn.oyqj.web.servlet;

import cn.oyqj.dao.UserDao;
import cn.oyqj.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()
		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