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/*
* SchedulerQueue.java February 2007
*
* Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
*
* 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 org.simpleframework.common.thread;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
/**
* The <code>SchedulerQueue</code> object is used to schedule tasks
* for execution. This queues the task for the requested period of
* time before it is executed. It ensures that the delay is adhered
* to such that tasks can be timed for execution in an accurate way.
*
* @author Niall Gallagher
*/
class SchedulerQueue {
/**
* This is the actual scheduler used to schedule the tasks.
*/
private final ScheduledThreadPoolExecutor executor;
/**
* This is the factory used to create the worker threads.
*/
private final ThreadFactory factory;
/**
* Constructor for the <code>SchedulerQueue</code> object. This
* will create a scheduler with a fixed number of threads to use
* before execution. Depending on the types of task that are
* to be executed this should be increased for accuracy.
*
* @param type this is the type of task to execute
* @param size this is the number of threads for the scheduler
*/
public SchedulerQueue(Class type, int size) {
this.factory = new DaemonFactory(type);
this.executor = new ScheduledThreadPoolExecutor(size, factory);
}
/**
* The <code>execute</code> method is used to queue the task for
* execution. If all threads are busy the provided task is queued
* and waits until all current and outstanding tasks are finished.
*
* @param task this is the task to be queued for execution
*/
public void execute(Runnable task) {
executor.execute(task);
}
/**
* This will execute the task within the executor after the time
* specified has expired. If the time specified is zero then it
* will be executed immediately. Once the scheduler has been
* stopped then this method will no longer accept runnable tasks.
*
* @param task this is the task to schedule for execution
* @param delay the time in milliseconds to wait for execution
*/
public void execute(Runnable task, long delay) {
execute(task, delay, TimeUnit.MILLISECONDS);
}
/**
* This will execute the task within the executor after the time
* specified has expired. If the time specified is zero then it
* will be executed immediately. Once the scheduler has been
* stopped then this method will no longer accept runnable tasks.
*
* @param task this is the task to schedule for execution
* @param delay this is the delay to wait before execution
* @param unit this is the duration time unit to wait for
*/
public void execute(Runnable task, long delay, TimeUnit unit) {
executor.schedule(task, delay, unit);
}
/**
* This is used to stop the executor by interrupting all running
* tasks and shutting down the threads within the pool. This will
* return once it has been stopped, and no further tasks will be
* accepted by this pool for execution.
*/
public void stop() {
stop(60000);
}
/**
* This is used to stop the executor by interrupting all running
* tasks and shutting down the threads within the pool. This will
* return once it has been stopped, and no further tasks will be
* accepted by this pool for execution.
*
* @param wait the number of milliseconds to wait for it to stop
*/
public void stop(long wait) {
if(!executor.isTerminated()) {
try {
executor.shutdown();
executor.awaitTermination(wait, MILLISECONDS);
} catch(Exception e) {
throw new IllegalStateException("Could not stop pool", e);
}
}
}
}
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