001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.util.concurrent;
018
019import java.util.concurrent.Callable;
020import java.util.concurrent.RejectedExecutionHandler;
021import java.util.concurrent.RunnableFuture;
022import java.util.concurrent.ScheduledThreadPoolExecutor;
023import java.util.concurrent.ThreadFactory;
024
025/**
026 * Scheduled thread pool executor that creates {@link RejectableFutureTask} instead of
027 * {@link java.util.concurrent.FutureTask} when registering new tasks for execution.
028 * <p/>
029 * Instances of {@link RejectableFutureTask} are required to handle {@link ThreadPoolRejectedPolicy#Discard} and
030 * {@link ThreadPoolRejectedPolicy#DiscardOldest} policies correctly, e.g. notify {@link Callable} and {@link Runnable}
031 * tasks when they are rejected. To be notified of rejection tasks have to implement {@link Rejectable} interface: <br/>
032 * <code><pre>
033 * public class RejectableTask implements Runnable, Rejectable {
034 *     &#064;Override
035 *     public void run() {
036 *         // execute task
037 *     }
038 *     &#064;Override
039 *     public void reject() {
040 *         // do something useful on rejection
041 *     }
042 * }
043 * </pre></code>
044 * <p/>
045 * If the task does not implement {@link Rejectable} interface the behavior is exactly the same as with ordinary
046 * {@link ScheduledThreadPoolExecutor}.
047 *
048 * @see RejectableFutureTask
049 * @see Rejectable
050 * @see RejectableThreadPoolExecutor
051 */
052public class RejectableScheduledThreadPoolExecutor extends ScheduledThreadPoolExecutor {
053
054    public RejectableScheduledThreadPoolExecutor(int corePoolSize) {
055        super(corePoolSize);
056    }
057
058    public RejectableScheduledThreadPoolExecutor(int corePoolSize, ThreadFactory threadFactory) {
059        super(corePoolSize, threadFactory);
060    }
061
062    public RejectableScheduledThreadPoolExecutor(int corePoolSize, RejectedExecutionHandler handler) {
063        super(corePoolSize, handler);
064    }
065
066    public RejectableScheduledThreadPoolExecutor(int corePoolSize, ThreadFactory threadFactory,
067                                                 RejectedExecutionHandler handler) {
068        super(corePoolSize, threadFactory, handler);
069    }
070
071    @Override
072    protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
073        if (runnable instanceof Rejectable) {
074            return new RejectableFutureTask<>(runnable, value);
075        } else {
076            return super.newTaskFor(runnable, value);
077        }
078    }
079
080    @Override
081    protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
082        if (callable instanceof Rejectable) {
083            return new RejectableFutureTask<>(callable);
084        } else {
085            return super.newTaskFor(callable);
086        }
087    }
088
089    @Override
090    public String toString() {
091        // the thread factory often have more precise details what the thread pool is used for
092        if (getThreadFactory() instanceof CamelThreadFactory) {
093            String name = ((CamelThreadFactory) getThreadFactory()).getName();
094            return super.toString() + "[" + name + "]";
095        } else {
096            return super.toString();
097        }
098    }
099
100}