bean实例化-实例工厂

• 实例工厂

  //UserDaoFactory.java 实例工厂
  public class UserDaoFactory {
      public UserDao getUserDao(){
          return new UserDaoImpl();
      }
  }
  // UserDao.java
  public interface UserDao {
      void save();
  }
  
  // UserDaoImpl.java 接口实现类
  public class UserDaoImpl implements UserDao {
      @Override
      public void save() {
          System.out.println("user dao save...");
      }
  }
  
  // AppForInstanceUser.java 测试类
  public class AppForInstanceUser {
      public static void main(String[] args) {
          // 创建实例化工厂对象
      /* UserDaoFactory userDaoFactory = new UserDaoFactory();
          // 通过实例化工厂对象创建对象
          UserDao userDao = userDaoFactory.getUserDao();
          userDao.save();*/
  
          ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
  
          UserDao userDao = (UserDao) ctx.getBean("userDao");
  
          userDao.save();
      }
  }
  

• 配置

  <!--applicationContext.xml-->
  <!--方式三：使用实例化工厂实例化bean-->
  <bean id="userFactory" class="com.charley.factory.UserDaoFactory"/>
  <bean id="userDao" factory-bean="userDaoFactory" factory-method="getUserDao"/>