JavaWeb学习-MVC基础开发系列-3-用户登录功能

「爱情、让人受尽委屈。」 2022-01-28 18:39 228阅读 0赞

这篇来实现用户登录功能，前面我们把所有类和接口都写好了。我们可以根据用户注册的写的过程，来完成用户登录。分别在每个层中添加登录相关的方法和逻辑。

1.在dao包的接口下新加findUser方法

package com.anthony.dao;
    
    import com.anthony.domain.User;
    
    public interface UserDao {
    	
    	/**
    	 * 添加用户信息
    	 * @param user
    	 * @throws Exception
    	 */
    	public void addUser(User user) throws Exception;
    	
    	/**
    	 * 查找用户，返回一个User对象，例如欢迎你 xxx就需要用到返回user对象
    	 * @param user
    	 * @return
    	 * @throws Exception
    	 */
    	public User findUser(User user) throws Exception;
    
    }

2.在dao.impl包下添加查找用户方法实现

package com.anthony.dao.impl;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.text.SimpleDateFormat;
    
    import com.anthony.dao.UserDao;
    import com.anthony.domain.User;
    import com.anthony.utils.DBUtils;
    
    public class UserDaoImpl implements UserDao {
    	
    	public void addUser(User user) throws Exception {
    		Connection conn = null;
    		PreparedStatement ps = null;
    		
    		try {
    			conn = DBUtils.getConnection();
    			ps = conn.prepareStatement("INSERT INTO users(username,password,email,birthday) VALUES(?,?,?,?)");
    			ps.setString(1, user.getUsername());
    			ps.setString(2, user.getPassword());
    			ps.setString(3, user.getEmail());
    			SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    			String date = sdf.format(user.getBirthday());
    			ps.setString(4, date);
    			//执行sql语句,这里是注册，插入数据
    			int i = ps.executeUpdate();
    		} catch (Exception e) {
    			e.printStackTrace();
    		}finally {
    			DBUtils.close(conn, ps, null);
    		}
    		
    	}
    
    	
    	public User findUser(User user) throws Exception {
    		Connection conn = null;
    		PreparedStatement ps = null;
    		ResultSet rs = null;
    		User u = null;
    		
    		try {
    			conn = DBUtils.getConnection();
    			ps = conn.prepareStatement("SELECT * FROM users WHERE username=? AND PASSWORD=?");
    			ps.setString(1, user.getUsername());
    			ps.setString(2, user.getPassword());
    			rs = ps.executeQuery();
    			if(rs.next()) {
    				u = new User();
    				u.setId(rs.getInt(1));
    				u.setUsername(rs.getString(2));
    				u.setPassword(rs.getString(3));
    				u.setEmail(rs.getString(4));
    				u.setBirthday(rs.getDate(5));
    			}
    		} catch (Exception e) {
    			e.printStackTrace();
    		}finally{
    			DBUtils.close(conn, ps, rs);
    		}
    		return u;
    	}
    
    }

3.在Service中接口，添加登录业务

package com.anthony.service;
    
    import com.anthony.domain.User;
    
    public interface UserService {
    	
    	/**
    	 * 用户注册
    	 * @param user
    	 * @throws Exception
    	 */
    	public void register(User user) throws Exception;
    	
    	/**
    	 * 用户登录
    	 * @param user
    	 * @return
    	 * @throws Exception
    	 */
    	public User login(User user) throws Exception;
    
    }

4.添加登录业务具体代码实现

package com.anthony.service.impl;
    
    import com.anthony.dao.UserDao;
    import com.anthony.dao.impl.UserDaoImpl;
    import com.anthony.domain.User;
    import com.anthony.service.UserService;
    
    public class UserServiceImpl implements UserService {
    	UserDao userDao = new UserDaoImpl();
    	
    	public void register(User user) throws Exception {
    		//业务层调DAO
    		userDao.addUser(user);
    	}
    
    	
    	public User login(User user) {
    		//业务层调DAO层
    		User u = null;
    		try {
    			u = userDao.findUser(user);
    		} catch (Exception e) {
    			e.printStackTrace();
    			//以后需要异常写入日志文件
    		}
    		return u;
    	}
    	
    }

5.写登录表单

创建一个login.jsp文件，然后在Index.jsp中登录链接跳转到login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>网站首页</title>
    </head>
    <body>
    	<a href="login.jsp">登录</a>
    	<a href="register.jsp">注册</a>
    
    </body>
    </html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>登录</title>
    </head>
    <body>
    	<form action="${pageContext.request.contextPath}/servlet/loginServlet" method="post">
    		用户名：<input type="text" name="username"><br/>
    		密码：<input type="password" name="password"><br/>
    		<input type="submit" value="登录"><br/>
    	</form>
    	
    </body>
    </html>

6.写登录Servlet

新建LoginServlet.java的servlet对象，访问url是/servlet/loginServlet

在web.xml添加如下内容

<servlet>
      	<servlet-name>loginServlet</servlet-name>
      	<servlet-class>com.anthony.web.servlet.LoginServlet</servlet-class>
      </servlet>
      
      <servlet-mapping>
      	<servlet-name>loginServlet</servlet-name>
      	<url-pattern>/servlet/loginServlet</url-pattern>
      </servlet-mapping>

LoginServlet.java内容如下

package com.anthony.web.servlet;
    
    import java.io.IOException;
    import java.lang.reflect.InvocationTargetException;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.apache.commons.beanutils.BeanUtils;
    
    import com.anthony.domain.User;
    import com.anthony.service.UserService;
    import com.anthony.service.impl.UserServiceImpl;
    
    
    public class LoginServlet extends HttpServlet {
    
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		req.setCharacterEncoding("UTF-8");
    		resp.setContentType("text/html;charset=UTF-8");
    		//获取表单数据
    		User user = new User();
    		try {
    			BeanUtils.populate(user, req.getParameterMap());
    			// 调用业务方法
    			UserService us = new UserServiceImpl();
    			user = us.login(user);
    		} catch (IllegalAccessException e) {
    			e.printStackTrace();
    		} catch (InvocationTargetException e) {
    			e.printStackTrace();
    		}
    		//分发转向
    		req.setAttribute("u", user);
    		req.getRequestDispatcher("/index.jsp").forward(req, resp);
    	}
    
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req,resp);
    	}
    	
    	
    
    }

这样部署之后，登录成功跳转到首页，用户来讲，不知道是否登录成功，所以，我们需要把Index.jsp修改一下

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>网站首页</title>
    </head>
    <body>
    	
    	<c:if test="${empty u}">
    		<a href="login.jsp">登录</a>
    		<a href="register.jsp">注册</a>
    	</c:if>
    	
    	<c:if test="${not empty u}">
    		欢迎您：${u.username}<a href="logoff.jsp">注销</a>
    	</c:if>
    </body>
    </html>

这里用到了JSTL语法，登录成功之后页面是这样的

![20190529212014361.png][]

[20190529212014361.png]: /images/20220126/4ed58dace56445358f53c3f0227d58bc.png