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>GenericFileRenameExclusiveReadLockStrategy waiting until its possible to
030     * rename the file.</li>
031     * <li>NewFileLockExclusiveReadLockStrategy acquiring a RW file lock for the duration
032     * of the processing.</li>
033     * <li>NewMarkerFileExclusiveReadLockStrategy using a marker file for acquiring
034     * read lock.</li>
035     * </ul>
036     */
037    public interface GenericFileExclusiveReadLockStrategy<T> {
038    
039        /**
040         * Acquires exclusive read lock to the file.
041         *
042         * @param operations generic file operations
043         * @param file       the file
044         * @param exchange   the exchange
045         * @return <tt>true</tt> if read lock was acquired. If <tt>false</tt> Camel
046         *         will skip the file and try it on the next poll
047         * @throws Exception can be thrown in case of errors
048         */
049        boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange) throws Exception;
050    
051        /**
052         * Releases the exclusive read lock granted by the <tt>acquireExclusiveReadLock</tt> method.
053         *
054         * @param operations generic file operations
055         * @param file       the file
056         * @param exchange   the exchange
057         * @throws Exception can be thrown in case of errors
058         */
059        void releaseExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange) throws Exception;
060    
061        /**
062         * Sets an optional timeout period.
063         * <p/>
064         * If the readlock could not be granted within the timeperiod then the wait is stopped and the
065         * <tt>acquireExclusiveReadLock</tt> method returns <tt>false</tt>.
066         *
067         * @param timeout period in millis
068         */
069        void setTimeout(long timeout);
070    
071    }