Java example source code file (AbstractScheduledEventExecutor.java)

This example Java source code file (AbstractScheduledEventExecutor.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstracteventexecutor, abstractscheduledeventexecutor, illegalargumentexception, override, priorityqueue, queue, runnable, scheduledfuturetask, threading, threads, timeunit, util

The AbstractScheduledEventExecutor.java Java example source code

/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project licenses this file to you 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.netty.util.concurrent;

import io.netty.util.internal.ObjectUtil;

import java.util.PriorityQueue;
import java.util.Queue;
import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * Abstract base class for {@link EventExecutor}s that want to support scheduling.
 */
public abstract class AbstractScheduledEventExecutor extends AbstractEventExecutor {

    Queue<ScheduledFutureTask scheduledTaskQueue;

    protected AbstractScheduledEventExecutor() {
    }

    protected AbstractScheduledEventExecutor(EventExecutorGroup parent) {
        super(parent);
    }

    protected static long nanoTime() {
        return ScheduledFutureTask.nanoTime();
    }

    Queue<ScheduledFutureTask scheduledTaskQueue() {
        if (scheduledTaskQueue == null) {
            scheduledTaskQueue = new PriorityQueue<ScheduledFutureTask();
        }
        return scheduledTaskQueue;
    }

    private static  boolean isNullOrEmpty(Queue<ScheduledFutureTask queue) {
        return queue == null || queue.isEmpty();
    }

    /**
     * Cancel all scheduled tasks.
     *
     * This method MUST be called only when {@link #inEventLoop()} is {@code true}.
     */
    protected void cancelScheduledTasks() {
        assert inEventLoop();
        Queue<ScheduledFutureTask scheduledTaskQueue = this.scheduledTaskQueue;
        if (isNullOrEmpty(scheduledTaskQueue)) {
            return;
        }

        final ScheduledFutureTask<?>[] scheduledTasks =
                scheduledTaskQueue.toArray(new ScheduledFutureTask<?>[scheduledTaskQueue.size()]);

        for (ScheduledFutureTask<?> task: scheduledTasks) {
            task.cancelWithoutRemove(false);
        }

        scheduledTaskQueue.clear();
    }

    /**
     * @see {@link #pollScheduledTask(long)}
     */
    protected final Runnable pollScheduledTask() {
        return pollScheduledTask(nanoTime());
    }

    /**
     * Return the {@link Runnable} which is ready to be executed with the given {@code nanoTime}.
     * You should use {@link #nanoTime()} to retrieve the the correct {@code nanoTime}.
     */
    protected final Runnable pollScheduledTask(long nanoTime) {
        assert inEventLoop();

        Queue<ScheduledFutureTask scheduledTaskQueue = this.scheduledTaskQueue;
        ScheduledFutureTask<?> scheduledTask = scheduledTaskQueue == null ? null : scheduledTaskQueue.peek();
        if (scheduledTask == null) {
            return null;
        }

        if (scheduledTask.deadlineNanos() <= nanoTime) {
            scheduledTaskQueue.remove();
            return scheduledTask;
        }
        return null;
    }

    /**
     * Return the nanoseconds when the next scheduled task is ready to be run or {@code -1} if no task is scheduled.
     */
    protected final long nextScheduledTaskNano() {
        Queue<ScheduledFutureTask scheduledTaskQueue = this.scheduledTaskQueue;
        ScheduledFutureTask<?> scheduledTask = scheduledTaskQueue == null ? null : scheduledTaskQueue.peek();
        if (scheduledTask == null) {
            return -1;
        }
        return Math.max(0, scheduledTask.deadlineNanos() - nanoTime());
    }

    final ScheduledFutureTask<?> peekScheduledTask() {
        Queue<ScheduledFutureTask scheduledTaskQueue = this.scheduledTaskQueue;
        if (scheduledTaskQueue == null) {
            return null;
        }
        return scheduledTaskQueue.peek();
    }

    /**
     * Returns {@code true} if a scheduled task is ready for processing.
     */
    protected final boolean hasScheduledTasks() {
        Queue<ScheduledFutureTask scheduledTaskQueue = this.scheduledTaskQueue;
        ScheduledFutureTask<?> scheduledTask = scheduledTaskQueue == null ? null : scheduledTaskQueue.peek();
        return scheduledTask != null && scheduledTask.deadlineNanos() <= nanoTime();
    }

    @Override
    public  ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
        ObjectUtil.checkNotNull(command, "command");
        ObjectUtil.checkNotNull(unit, "unit");
        if (delay < 0) {
            throw new IllegalArgumentException(
                    String.format("delay: %d (expected: >= 0)", delay));
        }
        return schedule(new ScheduledFutureTask<Void>(
                this, command, null, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
    }

    @Override
    public <V> ScheduledFuture schedule(Callable callable, long delay, TimeUnit unit) {
        ObjectUtil.checkNotNull(callable, "callable");
        ObjectUtil.checkNotNull(unit, "unit");
        if (delay < 0) {
            throw new IllegalArgumentException(
                    String.format("delay: %d (expected: >= 0)", delay));
        }
        return schedule(new ScheduledFutureTask<V>(
                this, callable, ScheduledFutureTask.deadlineNanos(unit.toNanos(delay))));
    }

    @Override
    public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
        ObjectUtil.checkNotNull(command, "command");
        ObjectUtil.checkNotNull(unit, "unit");
        if (initialDelay < 0) {
            throw new IllegalArgumentException(
                    String.format("initialDelay: %d (expected: >= 0)", initialDelay));
        }
        if (period <= 0) {
            throw new IllegalArgumentException(
                    String.format("period: %d (expected: > 0)", period));
        }

        return schedule(new ScheduledFutureTask<Void>(
                this, Executors.<Void>callable(command, null),
                ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), unit.toNanos(period)));
    }

    @Override
    public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
        ObjectUtil.checkNotNull(command, "command");
        ObjectUtil.checkNotNull(unit, "unit");
        if (initialDelay < 0) {
            throw new IllegalArgumentException(
                    String.format("initialDelay: %d (expected: >= 0)", initialDelay));
        }
        if (delay <= 0) {
            throw new IllegalArgumentException(
                    String.format("delay: %d (expected: > 0)", delay));
        }

        return schedule(new ScheduledFutureTask<Void>(
                this, Executors.<Void>callable(command, null),
                ScheduledFutureTask.deadlineNanos(unit.toNanos(initialDelay)), -unit.toNanos(delay)));
    }

    <V> ScheduledFuture schedule(final ScheduledFutureTask task) {
        if (inEventLoop()) {
            scheduledTaskQueue().add(task);
        } else {
            execute(new Runnable() {
                @Override
                public void run() {
                    scheduledTaskQueue().add(task);
                }
            });
        }

        return task;
    }

    final void removeScheduled(final ScheduledFutureTask<?> task) {
        if (inEventLoop()) {
            scheduledTaskQueue().remove(task);
        } else {
            execute(new Runnable() {
                @Override
                public void run() {
                    removeScheduled(task);
                }
            });
        }
    }
}