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.processor;
018    
019    import java.util.ArrayList;
020    import java.util.List;
021    
022    import org.apache.camel.Exchange;
023    import org.apache.camel.Navigate;
024    import org.apache.camel.Processor;
025    import org.apache.camel.impl.ServiceSupport;
026    import org.apache.camel.util.ServiceHelper;
027    
028    /**
029     * A Delegate pattern which delegates processing to a nested processor which can
030     * be useful for implementation inheritance when writing an {@link org.apache.camel.spi.Policy}
031     * 
032     * @version $Revision: 16362 $
033     */
034    public class DelegateProcessor extends ServiceSupport implements Processor, Navigate<Processor> {
035        protected Processor processor;
036    
037        public DelegateProcessor() {
038        }
039    
040        public DelegateProcessor(Processor processor) {
041            if (processor == this) {
042                throw new IllegalArgumentException("Recursive DelegateProcessor!");
043            }
044            this.processor = processor;
045        }
046    
047        public void process(Exchange exchange) throws Exception {
048            processNext(exchange);
049        }
050    
051        protected void processNext(Exchange exchange) throws Exception {
052            if (processor != null) {
053                processor.process(exchange);
054            }
055        }
056    
057        @Override
058        public String toString() {
059            return "Delegate[" + processor + "]";
060        }
061    
062        public Processor getProcessor() {
063            return processor;
064        }
065    
066        public void setProcessor(Processor processor) {
067            this.processor = processor;
068        }
069    
070        protected void doStart() throws Exception {
071            ServiceHelper.startServices(processor);
072        }
073    
074        protected void doStop() throws Exception {
075            ServiceHelper.stopServices(processor);
076        }
077    
078        /**
079         * Proceed with the underlying delegated processor
080         */
081        public void proceed(Exchange exchange) throws Exception {
082            processNext(exchange);
083        }
084    
085        public boolean hasNext() {
086            return processor != null;
087        }
088    
089        public List<Processor> next() {
090            if (!hasNext()) {
091                return null;
092            }
093            List<Processor> answer = new ArrayList<Processor>(1);
094            answer.add(processor);
095            return answer;
096        }
097    }