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     * @version $Revision: 14059 $
035     */
036    public class DefaultExchangeComparator implements ExpressionResultComparator<Exchange> {
037    
038        private Expression<Exchange> expression;
039    
040        public Expression<Exchange> getExpression() {
041            return expression;
042        }
043    
044        public void setExpression(Expression<Exchange> expression) {
045            this.expression = expression;
046        }
047    
048        @SuppressWarnings("unchecked")
049        public void setExpressions(List<Expression> expressions) {
050            if (expressions.isEmpty()) {
051                throw new IllegalArgumentException(
052                        "Expression required to resolve sequence number");
053            } else if (expressions.size() > 1) {
054                throw new IllegalArgumentException(
055                        "More than one expression currently not supported");
056            }
057            expression = expressions.get(0);
058        }
059    
060        public boolean predecessor(Exchange o1, Exchange o2) {
061            long n1 = getSequenceNumber(o1);
062            long n2 = getSequenceNumber(o2);
063            return n1 == (n2 - 1L);
064        }
065    
066        public boolean successor(Exchange o1, Exchange o2) {
067            long n1 = getSequenceNumber(o1);
068            long n2 = getSequenceNumber(o2);
069            return n2 == (n1 - 1L);
070        }
071    
072        public int compare(Exchange o1, Exchange o2) {
073            Long n1 = getSequenceNumber(o1);
074            Long n2 = getSequenceNumber(o2);
075            return n1.compareTo(n2);
076        }
077    
078        private long getSequenceNumber(Exchange exchange) {
079            return (Long)expression.evaluate(exchange);
080        }
081        
082    }