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     */
017    package org.apache.camel.util.concurrent;
018    
019    import java.util.concurrent.Callable;
020    import java.util.concurrent.RejectedExecutionHandler;
021    import java.util.concurrent.RunnableFuture;
022    import java.util.concurrent.ScheduledThreadPoolExecutor;
023    import 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 org.apache.camel.ThreadPoolRejectedPolicy#Discard}
030     * and {@link org.apache.camel.ThreadPoolRejectedPolicy#DiscardOldest} policies correctly, e.g. notify
031     * {@link Callable} and {@link Runnable} tasks when they are rejected.
032     * To be notified of rejection tasks have to implement {@link org.apache.camel.Rejectable} interface: <br/>
033     * <code><pre>
034     * public class RejectableTask implements Runnable, Rejectable {
035     *     &#064;Override
036     *     public void run() {
037     *         // execute task
038     *     }
039     *     &#064;Override
040     *     public void reject() {
041     *         // do something useful on rejection
042     *     }
043     * }
044     * </pre></code>
045     * <p/>
046     * If the task does not implement {@link org.apache.camel.Rejectable} interface the behavior is exactly the same as with
047     * ordinary {@link ScheduledThreadPoolExecutor}.
048     *
049     * @see RejectableFutureTask
050     * @see org.apache.camel.Rejectable
051     * @see RejectableThreadPoolExecutor
052     */
053    public class RejectableScheduledThreadPoolExecutor extends ScheduledThreadPoolExecutor {
054    
055        public RejectableScheduledThreadPoolExecutor(int corePoolSize) {
056            super(corePoolSize);
057        }
058    
059        public RejectableScheduledThreadPoolExecutor(int corePoolSize, ThreadFactory threadFactory) {
060            super(corePoolSize, threadFactory);
061        }
062    
063        public RejectableScheduledThreadPoolExecutor(int corePoolSize, RejectedExecutionHandler handler) {
064            super(corePoolSize, handler);
065        }
066    
067        public RejectableScheduledThreadPoolExecutor(int corePoolSize, ThreadFactory threadFactory, RejectedExecutionHandler handler) {
068            super(corePoolSize, threadFactory, handler);
069        }
070    
071        @Override
072        protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
073            return new RejectableFutureTask<T>(runnable, value);
074        }
075    
076        @Override
077        protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
078            return new RejectableFutureTask<T>(callable);
079        }
080    
081    }