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.activemq.transport.reliable;
018    
019    import java.io.IOException;
020    
021    /**
022     * Throws an exception if packets are dropped causing the transport to be
023     * closed.
024     * 
025     * 
026     */
027    public class ExceptionIfDroppedReplayStrategy implements ReplayStrategy {
028    
029        private int maximumDifference = 5;
030    
031        public ExceptionIfDroppedReplayStrategy() {
032        }
033    
034        public ExceptionIfDroppedReplayStrategy(int maximumDifference) {
035            this.maximumDifference = maximumDifference;
036        }
037    
038        public boolean onDroppedPackets(ReliableTransport transport, int expectedCounter, int actualCounter, int nextAvailableCounter) throws IOException {
039            int difference = actualCounter - expectedCounter;
040            long count = Math.abs(difference);
041            if (count > maximumDifference) {
042                throw new IOException("Packets dropped on: " + transport + " count: " + count + " expected: " + expectedCounter + " but was: " + actualCounter);
043            }
044    
045            // lets discard old commands
046            return difference > 0;
047        }
048    
049        public void onReceivedPacket(ReliableTransport transport, long expectedCounter) {
050        }
051    
052        public int getMaximumDifference() {
053            return maximumDifference;
054        }
055    
056        /**
057         * Sets the maximum allowed difference between an expected packet and an
058         * actual packet before an error occurs
059         */
060        public void setMaximumDifference(int maximumDifference) {
061            this.maximumDifference = maximumDifference;
062        }
063    
064    }