登录功能实现

编写前端登录页面

1.编写页面代码login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>系统登录 - 超市订单管理系统</title>
    <link type="text/css" rel="stylesheet" href="${pageContext.request.contextPath }/css/style.css" />
    <script type="text/javascript">
	/* if(top.location!=self.location){
	      top.location=self.location;
	 } */
    </script>
</head>
<body class="login_bg">
    <section class="loginBox">
        <header class="loginHeader">
            <h1>超市订单管理系统</h1>
        </header>
        <section class="loginCont">
	        <form class="loginForm" action="${pageContext.request.contextPath }/login.do"  name="actionForm" id="actionForm"  method="post" >
				<div class="info">${error }</div>
				<div class="inputbox">
                    <label for="userCode">用户名：</label>
					<input type="text" class="input-text" id="userCode" name="userCode" placeholder="请输入用户名" required/>
				</div>	
				<div class="inputbox">
                    <label for="userPassword">密码：</label>
                    <input type="password" id="userPassword" name="userPassword" placeholder="请输入密码" required/>
                </div>	
				<div class="subBtn">
					
                    <input type="submit" value="登录"/>
                    <input type="reset" value="重置"/>
                </div>	
			</form>
        </section>
    </section>
</body>
</html>

2.把这个登录页面设置为首页

如果不设置的话，默认首页为index.jsp

<!--设置欢迎页-->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>

Dao 层

1.编写Dao层得到用户登录的接口

import com.xy.pojo.User;
import java.sql.Connection;

public interface UserDao {
    //从数据库查询指定的用户,这里不需要获取连接数据库对象，交给业务层去做
    public User getLoginUser(Connection connection, String userCode);
}

2.编写Dao层的实现类

public class UserDaoImpl implements UserDao {
     public User getLoginUser(Connection connection, String userCode) throws SQLException {
         PreparedStatement statement = null;
         ResultSet rs = null;
         User user = null;
         if (connection != null){
             String sql = "select * from `smbms_user` where userCode=?";
             Object[] param = {userCode};
             rs = BaseDao.execute(connection, sql, param, statement, rs);
             while (rs.next()){
                 user = new User();
                 //将这些值丢给用户
                 user.setId(rs.getInt("id"));
                 user.setUserCode(rs.getString("userCode"));
                 user.setUserName(rs.getString("userName"));
                 user.setUserPassword(rs.getString("userPassword"));
                 user.setGender(rs.getInt("gender"));
                 user.setBirthday(rs.getDate("birthday"));
                 user.setPhone(rs.getString("phone"));
                 user.setAddress(rs.getString("address"));
                 user.setUserRole(rs.getInt("userRole"));
                 user.setCreatedBy(rs.getInt("createdBy"));
                 user.setModifyBy(rs.getInt("modifyBy"));
                 user.setModifyDate(rs.getDate("modifyDate"));
             }
             BaseDao.close(null,statement,rs);
         }
         return user;
     }
}

业务层

1.编写业务层接口

import com.xy.pojo.User;

import java.sql.SQLException;

public interface UserService {
    //用户登录
    public User login(String userCode, String password) throws SQLException;
}

2.编写业务层实现类

public class UserServiceImpl implements UserService{

    //业务层都会调用Dao层，所以我们要引入Dao层
    private UserDao userDao = null;
    public UserServiceImpl(){
        userDao = new UserDaoImpl();
    }
    public User login(String userCode, String password){
        Connection connection = null;
        User user = null;

        try {
            connection = BaseDao.getConnection();
            //通过业务层调取对应的具体的数据库的数据
            user = userDao.getLoginUser(connection,userCode);
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            BaseDao.close(connection,null,null);
        }

        return user;
    }
    @Test
    public void test(){
        UserServiceImpl userService = new UserServiceImpl();
        User admin = userService.login("admin", "1234567");
        System.out.println(admin.getUserPassword());
    }
}

Servlet

1.编写servlet：用于获取前端请求的参数，并调用业务层判断是否存在该用户

import com.xy.pojo.User;
import com.xy.service.user.UserService;
import com.xy.service.user.UserServiceImpl;
import com.xy.util.Constants;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.SQLException;

public class LoginServlet extends HttpServlet {
    //servlet控制层：调用业务层
    private UserService userService = new UserServiceImpl();
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("LoginServlet-start...");
        //获取前端数据
        String userCode = req.getParameter("userCode");
        String userPassword = req.getParameter("userPassword");
        User user = null;
        //调用业务层相应的操作:和数据库的用户做对比

        try {
            user = userService.login(userCode,userPassword);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
        if (user != null){
                //将用户的信息放到session中
                req.getSession().setAttribute(Constants.USER_SESSION,user);
                //跳转到主页
                resp.sendRedirect("jsp/frame.jsp");
            }else {
                //使用请求转发到登录页面，并提示用户名或密码错误
                req.setAttribute("error","用户名或密码不正确");
                req.getRequestDispatcher("/login.jsp").forward(req,resp);
            }
        }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

2.注册servlet

<servlet>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.xy.servlet.user.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login.do</url-pattern>
</servlet-mapping>