io.smartspaces.tasks.SimpleSequentialTaskQueue.java Source code

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Here is the source code for io.smartspaces.tasks.SimpleSequentialTaskQueue.java

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/*
 * Copyright (C) 2016 Keith M. Hughes
 * Copyright (C) 2012 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package io.smartspaces.tasks;

import io.smartspaces.system.SmartSpacesEnvironment;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;

import org.apache.commons.logging.Log;

/**
 * A task queue which will run its event handlers in First in, First Out
 * order.
 *
 * @author Keith M. Hughes
 */
public class SimpleSequentialTaskQueue implements SequentialTaskQueue {

    /**
     * The list of events to process.
     */
    private BlockingQueue<Runnable> tasks = new LinkedBlockingQueue<Runnable>();

    /**
     * The queue future, used for shutting the queue down.
     */
    private Future<?> queueFuture;

    /**
     * The space environment to run under.
     */
    private SmartSpacesEnvironment spaceEnvironment;

    /**
     * The logger for errors.
     */
    private Log log;

    /**
     * Construct a new task queue.
     *
     * @param spaceEnvironment
     *          the space environment the queue will use
     * @param log
     *          the logger to use
     */
    public SimpleSequentialTaskQueue(SmartSpacesEnvironment spaceEnvironment, Log log) {
        this.spaceEnvironment = spaceEnvironment;
        this.log = log;
    }

    @Override
    public void startup() {
        queueFuture = spaceEnvironment.getExecutorService().submit(new Runnable() {
            @Override
            public void run() {
                processTasks();
            }
        });
    }

    @Override
    public void shutdown() {
        if (queueFuture != null) {
            queueFuture.cancel(true);
            queueFuture = null;

            tasks.clear();
        }
    }

    @Override
    public void addTask(Runnable task) {
        try {
            tasks.put(task);
        } catch (InterruptedException e) {
            // Don't care
        }
    }

    /**
     * Process tasks until the task processing thread is interrupted.
     */
    private void processTasks() {
        try {
            while (!Thread.interrupted()) {
                processNextTask();
            }
        } catch (InterruptedException e) {
            // Don't care
        }
    }

    /**
     * Process the next event.
     *
     * @throws InterruptedException
     *           the thread got interrupted
     */
    private void processNextTask() throws InterruptedException {
        try {
            Runnable task = tasks.take();

            task.run();
        } catch (InterruptedException e) {
            throw e;
        } catch (Exception e) {
            log.error("Error during task processing", e);
        }
    }
}