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說明

復合的責任鏈，類似于管道模式，只要符合條件，說會向下傳遞，不會終止

演算法說明

• 按最高優先級去使用，符合就用，不符合就走下一個策略
• 具體鏈條,有點像pipeline管道模式
  • BlackHandler ip=172.17.0.11
  • RateLimitHandler header=is-black
  • WriteBlackHandler header=real-black

繼承抽象類

• AbstractHandler 抽象的責任處理者
  • 抽象方法action，需要各個子類【具體的責任處理者】自己去實作
  • final修飾的方法，封裝了實作細節，子類不能重寫
  • setNextHandler方法，設定下一個鏈條的【責任處理者】
• HandlerFactory 責任工廠
  • 通過一個責任處理串列，回傳一個責任鏈條
  • 責任鏈條可以持久化到資料庫里

責任鏈如果沒有終止條件，就類似于pipeline管道了

測驗代碼

抽象處理者

public abstract class AbstractHandler<T> {

	private AbstractHandler nextHandler;

	public final void setNextHandler(AbstractHandler nextHandler) {
		this.nextHandler = nextHandler;
	}

	protected abstract void action(T body);

	// final表示不允許子類重寫
	public final void handleRequest(T body) {
		action(body);

		if (this.nextHandler != null)
			this.nextHandler.handleRequest(body);
	}

}

具體處理者

public class BlackHandler extends AbstractHandler<Request> {

	private static final Logger logger = LoggerFactory.getLogger(CouponHandler.class);

	@Override
	public void action(Request body) {
		logger.info("BlackHandler 處理");
	}

}
public class RateLimitHandler extends AbstractHandler<Request> {

	private static final Logger logger = LoggerFactory.getLogger(CouponHandler.class);

	@Override
	protected void action(Request body) {
		logger.info("RateLimitHandler 處理");

	}

}
public class WriteBlackHandler extends AbstractHandler<Request> {

	private static final Logger logger = LoggerFactory.getLogger(CouponHandler.class);

	@Override
	protected void action(Request body) {
		logger.info("WriteBlackHandler 處理");

	}

}
public class EndHandler extends AbstractHandler<Request> {

	private static final Logger logger = LoggerFactory.getLogger(CouponHandler.class);

	@Override
	protected void action(Request body) {
		logger.info("EndHandler 處理");

	}

}

處理者工廠和請求資料體

public class HandlerFactory {

	public static <T extends Request> AbstractHandler<T> createHandler(List<AbstractHandler<T>> handlerModels) {
		AbstractHandler<T> handler = null;
		AbstractHandler<T> previousHandler = null;

		for (AbstractHandler<T> currentHandler : handlerModels.stream().collect(Collectors.toList())) {

			if (previousHandler != null) {
				previousHandler.setNextHandler(currentHandler);
			}
			else {
				handler = currentHandler;
			}
			previousHandler = currentHandler;

		}

		return handler;
	}

}
@AllArgsConstructor
@NoArgsConstructor
@Data
public class Request {

	private String ip;

	private String userId;

}

測驗用例

 public static void main(String[] args) {
		List<AbstractHandler<Request>> abstractHandlers = Arrays.asList(new RateLimitHandler(), new BlackHandler(),
				new WriteBlackHandler(),new EndHandler());
		AbstractHandler<Request> abstractHandler = HandlerFactory.createHandler(abstractHandlers);
		abstractHandler.handleRequest(new Request("1", "user1"));
	}

如果希望將你的責任鏈處理存盤到資料庫中，那個在handleFactory里，就需要介面className了,例如下面的代碼：

public static Handler handlerFactory() {
		List<HandlerModel> handlerModels = new ArrayList<>();
		handlerModels
				.add(new HandlerModel("CouponHandler", "com.lind.common.pattern.chinaorder.handler.CouponHandler", 1));
		handlerModels.add(
				new HandlerModel("DiscountHandler", "com.lind.common.pattern.chinaorder.handler.DiscountHandler", 2));
		handlerModels.add(
				new HandlerModel("BigGiftHandler", "com.lind.common.pattern.chinaorder.handler.BigGiftHandler", 3));
		handlerModels.add(new HandlerModel("VipHandler", "com.lind.common.pattern.chinaorder.handler.VipHandler", 4));
		return createHandler(handlerModels);
	}

	private static Handler createHandler(List<HandlerModel> handlerModels) {
		Handler handler = null;
		Handler previousHandler = null;

		for (HandlerModel handlerModel : handlerModels.stream().sorted().collect(Collectors.toList())) {
			try {
				Handler currentHandler = (Handler) Class.forName(handlerModel.getClassPath()).newInstance();
				if (previousHandler != null) {
					previousHandler.setNextHandler(currentHandler);
				}
				else {
					handler = currentHandler;
				}
				previousHandler = currentHandler;
			}
			catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
				throw new RuntimeException(e);
			}
		}

		return handler;
	}

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作者：倉儲大叔，張占嶺，
榮譽：微軟MVP
QQ：853066980

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