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.component.file;
018
019 import org.apache.camel.Exchange;
020
021 /**
022 * Strategy for acquiring exclusive read locks for files to be consumed. After
023 * granting the read lock it is realeased, we just want to make sure that when
024 * we start consuming the file its not currently in progress of being written by
025 * third party.
026 * <p/>
027 * Camel supports out of the box the following strategies:
028 * <ul>
029 * <li>FileRenameExclusiveReadLockStrategy waiting until its possible to rename the file.</li>
030 * <li>FileLockExclusiveReadLockStrategy acquiring a RW file lock for the duration of the processing.</li>
031 * <li>MarkerFileExclusiveReadLockStrategy using a marker file for acquiring read lock.</li>
032 * </ul>
033 */
034 public interface GenericFileExclusiveReadLockStrategy<T> {
035
036 /**
037 * Acquires exclusive read lock to the file.
038 *
039 * @param operations generic file operations
040 * @param file the file
041 * @param exchange the exchange
042 * @return <tt>true</tt> if read lock was acquired. If <tt>false</tt> Camel
043 * will skip the file and try it on the next poll
044 * @throws Exception can be thrown in case of errors
045 */
046 boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange) throws Exception;
047
048 /**
049 * Releases the exclusive read lock granted by the <tt>acquireExclusiveReadLock</tt> method.
050 *
051 * @param operations generic file operations
052 * @param file the file
053 * @param exchange the exchange
054 * @throws Exception can be thrown in case of errors
055 */
056 void releaseExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange) throws Exception;
057
058 /**
059 * Sets an optional timeout period.
060 * <p/>
061 * If the readlock could not be granted within the timeperiod then the wait is stopped and the
062 * <tt>acquireExclusiveReadLock</tt> method returns <tt>false</tt>.
063 *
064 * @param timeout period in millis
065 */
066 void setTimeout(long timeout);
067
068 }