大数据必学Java基础（一百零一）：BaseDAO抽取

package com.lanson.dao;
import com.lanson.pojo.Emp;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
public abstract class BaseDao {
    private static String driver ="com.mysql.cj.jdbc.Driver";
    private static String url="jdbc:mysql://127.0.0.1:3306/mydb?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai&allowPublicKeyRetrieval=true";
    private static String user="root";
    private static String password="root";
    public int baseUpdate(String sql,Object ... args){
        // 向 Emp表中增加一条数据
        Connection connection = null;
        PreparedStatement preparedStatement=null;
        int rows=0;
        try{
            Class.forName(driver);
            connection = DriverManager.getConnection(url, user,password);
            preparedStatement = connection.prepareStatement(sql);
            //设置参数
            for (int i = 0; i <args.length ; i++) {
                preparedStatement.setObject(i+1, args[i]);
            }
            //执行CURD
            rows =preparedStatement.executeUpdate();// 这里不需要再传入SQL语句
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(null != preparedStatement){
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if(null != connection){
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return rows;
    }
    public List baseQuery(Class clazz,String sql,Object ... args) {
        // 查询名字中包含字母A的员工信息
        Connection connection = null;
        PreparedStatement preparedStatement=null;
        ResultSet resultSet=null;
        List list =null;
        try{
            Class.forName(driver);
            connection = DriverManager.getConnection(url, user,password);
            preparedStatement = connection.prepareStatement(sql);//这里已经传入SQL语句
            //设置参数
            for (int i = 0; i <args.length ; i++) {
                preparedStatement.setObject(i+1, args[i]);
            }
            //执行CURD
            resultSet = preparedStatement.executeQuery();// 这里不需要再传入SQL语句
            list=new ArrayList() ;
            // 根据字节码获取所有 的属性
            Field[] fields = clazz.getDeclaredFields();
            for (Field field : fields) {
                field.setAccessible(true);// 设置属性可以 访问
            }
            while(resultSet.next()){
                // 通过反射创建对象
                Object obj = clazz.newInstance();//默认在通过反射调用对象的空参构造方法
                for (Field field : fields) {// 临时用Field设置属性
                    String fieldName = field.getName();// empno  ename job .... ...
                    Object data = resultSet.getObject(fieldName);
                    field.set(obj,data);
                }
                list.add(obj);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(null != resultSet){
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if(null != preparedStatement){
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if(null != connection){
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return list;
    }
}

package com.lanson.dao.impl;
import com.lanson.dao.BaseDao;
import com.lanson.dao.EmpDao;
import com.lanson.pojo.Emp;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
public class EmpDaoImpl extends BaseDao implements EmpDao {
    @Override
    public int addEmp(Emp emp) {
        String sql="insert into emp values(DEFAULT ,?,?,?,?,?,?,?)";
        return baseUpdate(sql, emp.getEname(),emp.getJob(),emp.getMgr(),emp.getHiredate(),emp.getSal(),emp.getComm(),emp.getDeptno());
    }
    @Override
    public int deleteByEmpno(int empno) {
        String sql="delete from emp where empno =?";
        return baseUpdate(sql, empno);
    }
    @Override
    public List<Emp> findAll() {
        String sql ="select * from emp";
        return baseQuery(Emp.class, sql );
    }
    @Override
    public int updateEmp(Emp emp) {
        String sql="update emp set ename =? ,job=?, mgr =?,hiredate =?,sal=?,comm=?,deptno=? where empno =?";
        return baseUpdate(sql, emp.getEname(),emp.getJob(),emp.getMgr(),emp.getHiredate(),emp.getSal(),emp.getComm(),emp.getDeptno(),emp.getEmpno());
    }
}

package com.lanson.dao.impl;
import com.lanson.dao.BaseDao;
import com.lanson.dao.DeptDao;
import com.lanson.pojo.Dept;
import com.lanson.pojo.Emp;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: Lansonli
 * @Description: MircoMessage:Mark_7001
 */
public class DeptDaoImpl extends BaseDao implements DeptDao {
    @Override
    public List<Dept> findAll() {
        String sql="select * from dept";
        return  baseQuery(Dept.class, sql);
    }
    @Override
    public int addDept(Dept dept) {
        String sql="insert into dept values(?,?,?)";
        return baseUpdate(sql, dept.getDeptno(),dept.getDname(),dept.getLoc());
    }
}