com.barchart.http.handlers.CancellableRequestHandler Maven / Gradle / Ivy

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/**
 * Copyright (C) 2011-2013 Barchart, Inc. 
 *
 * All rights reserved. Licensed under the OSI BSD License.
 *
 * http://www.opensource.org/licenses/bsd-license.php
 */
package com.barchart.http.handlers;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Future;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.barchart.http.request.RequestAttribute;
import com.barchart.http.request.RequestAttributeKey;
import com.barchart.http.request.RequestHandlerBase;
import com.barchart.http.request.ServerRequest;
import com.barchart.http.request.ServerResponse;

/**
 * Base class for stateless request handlers that want to register Futures that
 * will be cancelled if the client disconnects.
 */
public abstract class CancellableRequestHandler extends RequestHandlerBase {

	private static final Logger log = LoggerFactory
			.getLogger(CancellableRequestHandler.class);

	private final RequestAttributeKey ATTR_CANCEL_TASKS =
			new RequestAttributeKey("cancel-tasks");

	@Override
	public void onAbort(final ServerRequest request,
			final ServerResponse response) {

		cancelTasks(request);

	}

	@Override
	public void onException(final ServerRequest request,
			final ServerResponse response, final Throwable exception) {

		log.debug(
				"Request encountered an uncaught exception, cancelling tasks",
				exception);

		cancelTasks(request);

	}

	protected synchronized void cancelTasks(final ServerRequest request) {

		synchronized (ATTR_CANCEL_TASKS) {

			final List> tasks = request.attr(ATTR_CANCEL_TASKS).get();

			if (tasks != null) {
				for (final Future future : tasks) {
					if (!future.isDone()) {
						try {
							future.cancel(true);
						} catch (final Exception e) {
							// Swallow cancellation exceptions
							log.debug("Uncaught exception while cancelling", e);
						}
					}
				}
			}

		}

	}

	protected synchronized void cancelOnAbort(final ServerRequest request,
			final ServerResponse response, final Future future) {

		synchronized (ATTR_CANCEL_TASKS) {

			final RequestAttribute attr =
					request.attr(ATTR_CANCEL_TASKS);
			CancelFutureList tasks = attr.get();

			if (tasks == null) {
				tasks = new CancelFutureList();
				attr.set(tasks);
			}

			tasks.add(future);

		}

	}

	private class CancelFutureList extends ArrayList> {
		private static final long serialVersionUID = 1L;
	}

}