2.6 抽象工厂

1.定义
创建工厂的工厂。

2.优点
易于扩展不同的工厂和产品。

3.示例

public abstract class Video {
    abstract void produce();
}

public class JavaVideo extends Video {

    @Override
    void produce() {
        System.out.println("录制Java视频");
    }
}

public class PythonVideo extends Video {
    @Override
    void produce() {
        System.out.println("录制Python视频");
    }
}

public abstract class Article {
    abstract void produce();
}

public class JavaArticle extends Article {
    @Override
    void produce() {
        System.out.println("编写Java手记");
    }
}

public class PythonArticle extends Article {
    @Override
    void produce() {
        System.out.println("编写Python手记");
    }
}

public interface ICourseFactory {
    Video getVideo();

    Article getArticle();
}

public class JavaFactory implements ICourseFactory {
    @Override
    public Video getVideo() {
        return new JavaVideo();
    }

    @Override
    public Article getArticle() {
        return new JavaArticle();
    }
}

public class PythonFactory implements ICourseFactory {
    @Override
    public Video getVideo() {
        return new PythonVideo();
    }

    @Override
    public Article getArticle() {
        return new PythonArticle();
    }
}

public class Test {
    public static void main(String[] args) {
        ICourseFactory iCourseFactory = new JavaFactory();
        Video video = iCourseFactory.getVideo();
        video.produce();
        Article article = iCourseFactory.getArticle();
        article.produce();
    }
}

录制Java视频
编写Java手记

4.源码解析

public class DefaultSqlSessionFactory implements SqlSessionFactory {
  private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
    Transaction tx = null;
    try {
      final Environment environment = configuration.getEnvironment();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
      tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
      final Executor executor = configuration.newExecutor(tx, execType);
      return new DefaultSqlSession(configuration, executor, autoCommit);
    } catch (Exception e) {
      closeTransaction(tx); // may have fetched a connection so lets call close()
      throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }
}