19_傳智播客JDBC_使用DAO工廠模式（代碼超經典）

原創

nttwbd

2020-02-20 15:00

package five.test.daoFaction;

import java.io.InputStream;
import java.util.Properties;

import five.dao.UserDao;

public class DaoFactory {

// 簡單工廠模式 && 單例模式
private static UserDao ud = null;
private static DaoFactory instance = new DaoFactory();

// 單例模式構造方法私有
private DaoFactory(){
  try {
   Properties properties = new Properties();
   //InputStream inputStream = new FileInputStream(new File("src/daoconfig.properties"));

   //通過ClassLoader 來得到配置的文件
   InputStream inputStream = DaoFactory.class.getClassLoader()
     .getResourceAsStream("daoconfig.properties");
   properties.load(inputStream);
   String className = properties.getProperty("userDaoClass");

   Class myClass = Class.forName(className);
   ud = (UserDao) myClass.newInstance();
  } catch (Exception e) {
   // 如果再讀取配置文件時出錯，拋出系統啓動異常
   throw new ExceptionInInitializerError(e);
  }
}

    public static DaoFactory getInstance() {
  return instance;
}

    public UserDao getUserDao() {
  return ud;
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package five.test;

import java.sql.Date;

import five.dao.UserDao;
import five.domain.User;
import five.test.daoFaction.DaoFactory;

public class UserDaoTest {

public static void main(String[] args) {
  User user = new User(20, null, "20pass", null, 0);
  user.setBrithday(new Date(0));
  user.setName("dao name1");
  user.setMonney(1000.0f);

  //依賴具體實現[new UserDaoImpl();]
  //對策工廠模式通過配置文件
  //存在修改代碼的可能，在不修改代碼的前提下
  //就只能修改配置文件
  //UserDao ud = new UserDaoImpl();
  UserDao ud = DaoFactory.getInstance().getUserDao();

  ud.addUser(user);
  user = ud.getUser(20);

  System.out.print(user.getPassword());
}
}