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The Core Camel Java DSL based router
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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.camel.processor;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.DelegateProcessor;
import org.apache.camel.Exchange;
import org.apache.camel.Navigate;
import org.apache.camel.Processor;
import org.apache.camel.spi.AsyncProcessorAwaitManager;
import org.apache.camel.support.ServiceSupport;
import org.apache.camel.util.AsyncProcessorConverterHelper;
import org.apache.camel.util.ServiceHelper;

/**
 * A Delegate pattern which delegates processing to a nested {@link AsyncProcessor} which can
 * be useful for implementation inheritance when writing an {@link org.apache.camel.spi.Policy}
 * 
 * Important: This implementation does support the asynchronous routing engine.
 * If you are implementing a EIP pattern please use this as the delegate.
 *
 * @version
 * @see DelegateSyncProcessor
 * @see org.apache.camel.processor.DelegateProcessor
 */
public class DelegateAsyncProcessor extends ServiceSupport implements DelegateProcessor, AsyncProcessor, Navigate {
    protected AsyncProcessor processor;

    public DelegateAsyncProcessor() {
    }

    public DelegateAsyncProcessor(AsyncProcessor processor) {
        if (processor == this) {
            throw new IllegalArgumentException("Recursive DelegateAsyncProcessor!");
        }
        this.processor = processor;
    }

    public DelegateAsyncProcessor(Processor processor) {
        this(AsyncProcessorConverterHelper.convert(processor));
    }

    @Override
    public String toString() {
        return "DelegateAsync[" + processor + "]";
    }

    public AsyncProcessor getProcessor() {
        return processor;
    }

    public void setProcessor(AsyncProcessor processor) {
        this.processor = processor;
    }

    public void setProcessor(Processor processor) {
        this.processor = AsyncProcessorConverterHelper.convert(processor);
    }

    protected void doStart() throws Exception {
        ServiceHelper.startServices(processor);
    }

    protected void doStop() throws Exception {
        ServiceHelper.stopServices(processor);
    }

    protected void doShutdown() throws Exception {
        ServiceHelper.stopAndShutdownServices(processor);
    }

    public void process(Exchange exchange) throws Exception {
        // inline org.apache.camel.util.AsyncProcessorHelper.process(org.apache.camel.AsyncProcessor, org.apache.camel.Exchange)
        // to optimize and reduce stacktrace lengths
        final AsyncProcessorAwaitManager awaitManager = exchange.getContext().getAsyncProcessorAwaitManager();
        final CountDownLatch latch = new CountDownLatch(1);
        // call the asynchronous method and wait for it to be done
        boolean sync = process(exchange, new AsyncCallback() {
            public void done(boolean doneSync) {
                if (!doneSync) {
                    awaitManager.countDown(exchange, latch);
                }
            }
        });
        if (!sync) {
            awaitManager.await(exchange, latch);
        }
    }

    public boolean process(final Exchange exchange, final AsyncCallback callback) {
        return processor.process(exchange, callback);
    }

    /**
     * @deprecated use {@link #process(org.apache.camel.Exchange, org.apache.camel.AsyncCallback)} instead
     */
    @Deprecated
    protected boolean processNext(Exchange exchange, AsyncCallback callback) {
        throw new UnsupportedOperationException("This method is deprecated, use process(Exchange, AsyncCallback) instead");
    }

    public boolean hasNext() {
        return processor != null;
    }

    public List next() {
        if (!hasNext()) {
            return null;
        }
        List answer = new ArrayList(1);
        answer.add(processor);
        return answer;
    }

}