桥接模式

设计模式 评论

桥接模式

属于结构型模式

桥接模式将抽象和实现分离开来,各自独立,但能动态的结合;

为什么使用桥接模式

桥接模式基于类的最小设计原则, 通过使用封装、聚合及继承，让不同的类承担不同的职责；
将事物的抽象和实现分离， 从而保持各部分的独立性功能的扩展性；

使用桥接模式

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// 抽象事物 消息
public abstract class AbstractMessage {
    public AbstractMessage(MessageImplementor messageImplementor) {
        this.messageImplementor = messageImplementor;
    }

    private MessageImplementor messageImplementor;

    public void sendMessage(String message, String toUser){
        this.messageImplementor.send(message,toUser);
    }
}

// 抽象的子类, 默认消息
public class DefaultMessage extends AbstractMessage {
    public DefaultMessage(MessageImplementor messageImplementor) {
        super(messageImplementor);
    }

    @Override
    public void sendMessage(String message, String toUser) {
        super.sendMessage(message, toUser);
    }
}

// 抽象的子类, 加急消息
public class UrgencyMessage extends AbstractMessage {
    @Override
    public void sendMessage(String message, String toUser) {
        super.sendMessage("加急"+message, toUser);
    }

    public UrgencyMessage(MessageImplementor messageImplementor) {
        super(messageImplementor);
    }
}

// 抽象的子类, 特快消息
public class ExpressMessage extends AbstractMessage {
    public ExpressMessage(MessageImplementor messageImplementor) {
        super(messageImplementor);
    }

    @Override
    public void sendMessage(String message, String toUser) {
        super.sendMessage("特快"+message, toUser);
    }
}

// 行为接口
public interface MessageImplementor {
    void send(String message,String toUser);
}

// 行为的实现, 用邮件发
public class MessageMail implements MessageImplementor {
    @Override
    public void send(String message, String toUser) {
        System.out.println("用邮件给 "+toUser+" 发送: "+message);
    }
}

// 行为的实现, 用微信发
public class MessageWeChat implements MessageImplementor {
    @Override
    public void send(String message, String toUser) {
        System.out.println("用微信给 "+toUser+" 发送: "+message);
    }
}

//测试
@Test
public void testBridging(){
    AbstractMessage message1=new DefaultMessage(new MessageMail());
    AbstractMessage message2=new DefaultMessage(new MessageWeChat());
    AbstractMessage message3=new UrgencyMessage(new MessageMail());
    AbstractMessage message4=new UrgencyMessage(new MessageWeChat());
    AbstractMessage message5=new ExpressMessage(new MessageMail());
    AbstractMessage message6=new ExpressMessage(new MessageWeChat());
    message1.sendMessage("在吗","小明");
    message2.sendMessage("在吗","小明");
    message3.sendMessage("在吗","小明");
    message4.sendMessage("在吗","小明");
    message5.sendMessage("在吗","小明");
    message6.sendMessage("在吗","小明");
}

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