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;
018
019import java.util.concurrent.CountDownLatch;
020
021import org.apache.camel.AsyncCallback;
022import org.apache.camel.AsyncProcessor;
023import org.apache.camel.Exchange;
024import org.apache.camel.spi.AsyncProcessorAwaitManager;
025import org.apache.camel.spi.UnitOfWork;
026import org.slf4j.Logger;
027import org.slf4j.LoggerFactory;
028
029/**
030 * Helper methods for {@link AsyncProcessor} objects.
031 */
032public final class AsyncProcessorHelper {
033
034    private static final Logger LOG = LoggerFactory.getLogger(AsyncProcessorHelper.class);
035
036    private AsyncProcessorHelper() {
037        // utility class
038    }
039
040    /**
041     * Calls the async version of the processor's process method.
042     * <p/>
043     * This implementation supports transacted {@link Exchange}s which ensure those are run in a synchronous fashion.
044     * See more details at {@link org.apache.camel.AsyncProcessor}.
045     *
046     * @param processor the processor
047     * @param exchange  the exchange
048     * @param callback  the callback
049     * @return <tt>true</tt> to continue execute synchronously, <tt>false</tt> to continue being executed asynchronously
050     * @deprecated should no longer be needed, instead invoke the process method on the {@link AsyncProcessor} directly,
051     * instead of using this method.
052     */
053    @Deprecated
054    public static boolean process(final AsyncProcessor processor, final Exchange exchange, final AsyncCallback callback) {
055        boolean sync;
056
057        if (exchange.isTransacted()) {
058            // must be synchronized for transacted exchanges
059            LOG.trace("Transacted Exchange must be routed synchronously for exchangeId: {} -> {}", exchange.getExchangeId(), exchange);
060            try {
061                process(processor, exchange);
062            } catch (Throwable e) {
063                exchange.setException(e);
064            }
065            callback.done(true);
066            sync = true;
067        } else {
068            final UnitOfWork uow = exchange.getUnitOfWork();
069
070            // allow unit of work to wrap callback in case it need to do some special work
071            // for example the MDCUnitOfWork
072            AsyncCallback async = callback;
073            if (uow != null) {
074                async = uow.beforeProcess(processor, exchange, callback);
075            }
076
077            // we support asynchronous routing so invoke it
078            sync = processor.process(exchange, async);
079
080            // execute any after processor work (in current thread, not in the callback)
081            if (uow != null) {
082                uow.afterProcess(processor, exchange, callback, sync);
083            }
084        }
085
086        if (LOG.isTraceEnabled()) {
087            LOG.trace("Exchange processed and is continued routed {} for exchangeId: {} -> {}",
088                    new Object[]{sync ? "synchronously" : "asynchronously", exchange.getExchangeId(), exchange});
089        }
090        return sync;
091    }
092
093    /**
094     * Calls the async version of the processor's process method and waits
095     * for it to complete before returning. This can be used by {@link AsyncProcessor}
096     * objects to implement their sync version of the process method.
097     * <p/>
098     * <b>Important:</b> This method is discouraged to be used, as its better to invoke the asynchronous
099     * {@link AsyncProcessor#process(org.apache.camel.Exchange, org.apache.camel.AsyncCallback)} method, whenever possible.
100     *
101     * @param processor the processor
102     * @param exchange  the exchange
103     * @throws Exception can be thrown if waiting is interrupted
104     */
105    public static void process(final AsyncProcessor processor, final Exchange exchange) throws Exception {
106        final AsyncProcessorAwaitManager awaitManager = exchange.getContext().getAsyncProcessorAwaitManager();
107
108        final CountDownLatch latch = new CountDownLatch(1);
109        boolean sync = processor.process(exchange, new AsyncCallback() {
110            public void done(boolean doneSync) {
111                if (!doneSync) {
112                    awaitManager.countDown(exchange, latch);
113                }
114            }
115
116            @Override
117            public String toString() {
118                return "Done " + processor;
119            }
120        });
121        if (!sync) {
122            awaitManager.await(exchange, latch);
123        }
124    }
125
126}