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;
018    
019    /**
020     * An <b>asynchronous</b> processor which can process an {@link Exchange} in an asynchronous fashion
021     * and signal completion by invoking the {@link AsyncCallback}.
022     * <p/>
023     * Any processor can be coerced to have an {@link AsyncProcessor} interface by using the
024     * {@link org.apache.camel.impl.converter.AsyncProcessorTypeConverter#convert AsyncProcessorTypeConverter.covert}
025     * method.
026     * <p/>
027     * <b>Important:<b/> Use the {@link org.apache.camel.util.AsyncProcessorHelper#process(AsyncProcessor, Exchange, AsyncCallback)}
028     * method to invoke the process method, which ensure Camel have a chance to interweave and invoke it in a reliable manner.
029     * For example when using transactions all the invocations has to occur in synchronous manner to ensure the transaction
030     * work is done in the same thread, which is required by Spring TransactionManager.
031     *
032     * @version 
033     */
034    public interface AsyncProcessor extends Processor {
035    
036        /**
037         * Processes the message exchange.
038         * Similar to {@link Processor#process}, but the caller supports having the exchange asynchronously processed.
039         * <p/>
040         * If there was a failure processing then the caused {@link Exception} would be set on the {@link Exchange}.
041         *
042         * @param exchange the message exchange
043         * @param callback the {@link AsyncCallback} will be invoked when the processing of the exchange is completed.
044         *                 If the exchange is completed synchronously, then the callback is also invoked synchronously.
045         *                 The callback should therefore be careful of starting recursive loop.
046         * @return (doneSync) <tt>true</tt> to continue execute synchronously, <tt>false</tt> to continue being executed asynchronously
047         * @see org.apache.camel.util.AsyncProcessorHelper#process(AsyncProcessor, Exchange, AsyncCallback)
048         */
049        boolean process(Exchange exchange, AsyncCallback callback);
050    }