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.resequencer;
018    
019    import java.util.List;
020    
021    import org.apache.camel.Exchange;
022    import org.apache.camel.Expression;
023    
024    /**
025     * Compares elements of an {@link Exchange} sequence by comparing
026     * <code>long</code> values returned by this comaprator's
027     * <code>expression</code>. The expression is set during route definition
028     * e.g.
029     * 
030     * <pre>
031     *    ...resequencer(header(&quot;seqnum&quot;)).stream()...
032     * </pre>
033     * 
034     * @author Martin Krasser
035     * 
036     * @version $Revision: 303 $
037     */
038    public class DefaultExchangeComparator implements ExpressionResultComparator<Exchange> {
039    
040        private Expression<Exchange> expression;
041    
042        public Expression<Exchange> getExpression() {
043            return expression;
044        }
045    
046        public void setExpression(Expression<Exchange> expression) {
047            this.expression = expression;
048        }
049    
050        @SuppressWarnings("unchecked")
051        public void setExpressions(List<Expression> expressions) {
052            if (expressions.isEmpty()) {
053                throw new IllegalArgumentException(
054                        "Expression required to resolve sequence number");
055            } else if (expressions.size() > 1) {
056                throw new IllegalArgumentException(
057                        "More than one expression currently not supported");
058            }
059            expression = expressions.get(0);
060        }
061    
062        public boolean predecessor(Exchange o1, Exchange o2) {
063            long n1 = getSequenceNumber(o1);
064            long n2 = getSequenceNumber(o2);
065            return n1 == (n2 - 1L);
066        }
067    
068        public boolean successor(Exchange o1, Exchange o2) {
069            long n1 = getSequenceNumber(o1);
070            long n2 = getSequenceNumber(o2);
071            return n2 == (n1 - 1L);
072        }
073    
074        public int compare(Exchange o1, Exchange o2) {
075            Long n1 = getSequenceNumber(o1);
076            Long n2 = getSequenceNumber(o2);
077            return n1.compareTo(n2);
078        }
079    
080        private long getSequenceNumber(Exchange exchange) {
081            return (Long)expression.evaluate(exchange);
082        }
083        
084    }