Dao类

package Dao;

import java.sql.ResultSet;
import java.sql.SQLException;
import Entity.Admin;


/**
 *
 * @author llq
 *管理员数据库操作封装
 */
public class AdminDao extends BaseDao {
    //将从表单获取到的username和password作为参数传入，返回一个在数据库的user表中对应了用户名和密码的user对象
    /*
     * 1、如果成功返回一个user对象说明在数据库中找到和表单输入对应的用户名和密码，登录成功
     * 2、如果返回为空说明在数据库中没有找到和表单对应的用户名和密码，登录失败*/
    public Admin login(String username , String password){
        String sql = "select * from Admin where username = '" + username + "' and password = '" + password + "'";
        ResultSet resultSet = query(sql);
        try {
            if(resultSet.next()){
                Admin admin = new Admin();
                admin.setId(resultSet.getInt("id"));
                admin.setUsername(resultSet.getString("username"));
                admin.setPassword(resultSet.getString("password"));
                return admin;
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

package Dao;

import Entity.Finance;

import java.sql.ResultSet;
import java.sql.SQLException;

public class FinanceDao extends BaseDao {
    public Finance login(String tno, String password)
    {
        String sql="select * from  Finance where tno = '" + tno + "' and password = '" + password + "'";
        ResultSet resultSet = query(sql);
        try {
            if(resultSet.next()){
                Finance finance = new Finance();
                finance.setId(resultSet.getInt("id"));
                finance.setTno(resultSet.getString("tno"));
                finance.setPassword(resultSet.getString("password"));
                return finance;
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

package Dao;


import Entity.Manager;

import java.sql.ResultSet;
import java.sql.SQLException;

public class ManagerDao extends BaseDao{
    public Manager login(String sno, String password)
    {
        String sql = "select * from  Manager where sno = '" + sno + "' and password = '" + password + "'";
        ResultSet resultSet = query(sql);
        try {
            if(resultSet.next()){
                Manager manager = new Manager();
                manager.setId(resultSet.getInt("id"));
                manager.setSno(resultSet.getString("sno"));
                manager.setPassword(resultSet.getString("password"));
                return manager;
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

package Dao;

import Entity.Staff;

import java.sql.ResultSet;
import java.sql.SQLException;

public class StaffDao extends BaseDao{
    public Staff login(String sno, String password)
    {
        String sql = "select * from  Staff where sno = '" + sno + "' and password = '" + password + "'";
        ResultSet resultSet = query(sql);
        try {
            if(resultSet.next()){
                Staff staff = new Staff();
                staff.setId(resultSet.getInt("id"));
                staff.setSno(resultSet.getString("sno"));
                staff.setPassword(resultSet.getString("password"));
                return staff;
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

package Dao;


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

/**
 *
 * @author llq
 *基础dao，封装基本操作
 */
public class BaseDao {
    private DbUtil dbUtil = new DbUtil();
    /**
     * 及时关闭数据库连接，释放资源
     */
    public void closeCon(){
        dbUtil.closeCon();
    }

    /**
     * 基础查询，多条查询
     */
    public ResultSet query(String sql){
        try {
            PreparedStatement prepareStatement = dbUtil.getConnection().prepareStatement(sql);
            return prepareStatement.executeQuery();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null ;
    }
    /**
     *增删改
     */
    public boolean update(String sql){
        try {
            return dbUtil.getConnection().prepareStatement(sql).executeUpdate() > 0;
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return false;
    }
    public Connection getConnection(){
        return dbUtil.getConnection();
    }
}