SMBMS项目实战（登录功能实现）

流程图：

 1）编写前端界面

 2）在web.xml中设置欢迎页面（首页）

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

 3）编写dao层登录用户登录的接口

// 设置为面向接口编程的格式
public interface UserDao {
    // 得到登录的用户
    public User getLoginUser(Connection connection, String userCode) throws SQLException;
}

4）编写dao接口的实现类

package com.mine.dao.user;

import com.mine.dao.BaseDao;
import com.mine.pojo.User;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDaoImpl implements UserDao {
    // 去数据库中查询得到用户
    public User getLoginUser(Connection connection, String userCode) throws SQLException {

        // 1）准备三个对象
        PreparedStatement pstm = null; // 因为下面执行函数execute需要这两个参数，所以在这初始化
        ResultSet rs = null;   // 结果
        User user = null; // 可能会查出来的用户


        // 2）判断数据库连接是否成功
        if (connection != null) {
            // 3)如果连接成功了，丢一个sql
            String sql = "select * from smbms_user where userCode=?"; // 用问号保证安全
            Object[] params = {userCode}; // 封装参数，它就是唯一的数据

            // 4)执行sql
            // sql也好了，userCode也好了，接下来需要PreparedStatement和ResultSet就可以调用执行方法了
            rs = BaseDao.execute(connection, pstm, rs, sql, params);
            // 遍历用户信息
            if (rs.next()) {
                user = new User(); // new 一个User对象
                user.setId(rs.getInt("id")); // 设置id为查出来的对象的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.setCreationDate(rs.getTimestamp("creationDate"));
                user.setModifyBy(rs.getInt("modifyBy"));
                user.setModifyDate(rs.getTimestamp("modifyDate"));
            }
            // 上面这些是从数据库查出来的，查完要关闭数据库
            BaseDao.closeResource(null, pstm, rs);
            // 最后返回user


        }
        return user;

    }
}

5）业务层接口

public interface UserService {
    // 用户登录,去公司写的大多就是这个业务层
    public User login(String userCode, String password) throws SQLException;
}

6）业务层实现类

package com.mine.service.user;

import com.mine.dao.BaseDao;
import com.mine.dao.user.UserDao;
import com.mine.dao.user.UserDaoImpl;
import com.mine.pojo.User;
import org.junit.Test;

import java.sql.Connection;
import java.sql.SQLException;

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;
    public UserServiceImpl() {
        userDao = new UserDaoImpl();
    }
    /*
       userCode:用户名
       password:密码

     */
    // 调这个方法的人就能拿到用户
    public User login(String userCode, String password) {
        Connection connection = null;
        User user = null;


        try {
            connection = BaseDao.getConnection(); // 建立连接
            // 通过业务层调用对应的具体的数据库操作
            user = userDao.getLoginUser(connection, userCode);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            BaseDao.closeResource(connection, null, null);
        }
        return user;
    }

    @Test   // 这个是在junit包里面的，所以要引入junit包
    public void test() {
        UserServiceImpl userService = new UserServiceImpl();
        User admin = userService.login("admin", "1234567");
        System.out.println(admin.getUserPassword());
    }
}

7）编写servlet

package com.mine.servlet.user;

import com.mine.pojo.User;
import com.mine.service.user.UserService;
import com.mine.service.user.UserServiceImpl;
import com.mine.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。去调业务层的代码，要么私有进来，要么去new
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("LoginServlet -- start....");

        // 获取用户名和密码,去前端拿
        String userCode = req.getParameter("userCode");
        String userPassword = req.getParameter("userPassword");

        // 和数据库中的密码进行对比，调业务层
        UserService userService = new UserServiceImpl();
        try {
            User user = userService.login(userCode, userPassword); // 这里已经把登录的人查出来
            if (user != null) { // 查有此人，可以登录
                // 将用户的信息放到session中
                req.getSession().setAttribute(Constants.USER_SESSION, user);
                // 登录成功之后跳转到内部主页
                resp.sendRedirect("jsp/frame.jsp");

            } else { // 查无此人，无法登录
                // 转发回登录页面，顺带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);

            }
        } catch (SQLException e) {
            e.printStackTrace();
        }


    }

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

上面代码中的

Constants.USER_SESSION

8)注册servlet

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

9）测试访问，确保以上成功

出现bug：用户名和密码都正确，但是就是没有跳转到下一个页面，而是提示错误

错误信息：java.sql.SQLException: No suitable driver found for jdbc:mysql:/localhost:3306?useUnicode=true&characterEncoding=utf-8

 

 preparedStatement = connection.prepareStatement(sql)和resultSet = preparedStatement.executeQuery(sql)是功能相同的两行代码。所以会报错。

登录功能优化：

注销功能：思路：移除session,返回登录页面

package com.mine.servlet.user;

import com.mine.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;

public class LogoutServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 移除用户的session
        req.getSession().removeAttribute(Constants.USER_SESSION);
        // 回到登录页面
        resp.sendRedirect("/login.jsp");
    }

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

注册

<servlet>
        <servlet-name>LogoutServlet</servlet-name>
        <servlet-class>com.mine.servlet.user.LogoutServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LogoutServlet</servlet-name>
        <url-pattern>/jsp/logout.do</url-pattern>
    </servlet-mapping>

 出现bug 404

解决方案：

登录拦截优化：

编写一个过滤器

package com.mine.filter;

import com.mine.pojo.User;
import com.mine.util.Constants;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.HttpRetryException;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class SysFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;  // 这个为了获取session
        HttpServletResponse response = (HttpServletResponse) resp; // 这个为了重定向

        // 过滤器从session中获取用户，如果把session移除掉，它一定获取不到
        User user = (User) request.getSession().getAttribute(Constants.USER_SESSION);

        if (user == null) { // 如果用户为空，说明session已经被移除或者注销了或者未登录,那就让它走error.jsp
            response.sendRedirect("/smbms/error.jsp");

        } else {
            chain.doFilter(req, resp);
        }
    }

    @Override
    public void destroy() {

    }
}

配置

<!--    用户登录过滤器-->
    <filter>
        <filter-name>SysFilter</filter-name>
        <filter-class>com.mine.filter.SysFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>SysFilter</filter-name>
        <url-pattern>/jsp/*</url-pattern>   <!-- jsp下面的所有页面 -->
    </filter-mapping>

注：如果error.jsp访问找不到资源，把error改个名即可访问

bug: