001package org.apache.commons.jcs3.utils.access;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *   http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022/**
023 * Interface for doing a piece of work which is expected to be cached. This is
024 * meant to be used in conjunction with JCSWorker.
025 * <p>
026 * Implement doWork() to return the work being done. isFinished() should return
027 * false until setFinished(true) is called, after which time it should return
028 * true.
029 * </p>
030 */
031public interface JCSWorkerHelper<V>
032{
033    /**
034     * Tells us whether or not the work has been completed. This will be called
035     * automatically by JCSWorker. You should not call it yourself.
036     * <p>
037     * @return True if the work has already been done, otherwise false.
038     */
039    boolean isFinished();
040
041    /**
042     * Sets whether or not the work has been done.
043     * <p>
044     * @param isFinished
045     *            True if the work has already been done, otherwise false.
046     */
047    void setFinished( boolean isFinished );
048
049    /**
050     * The method to implement to do the work that should be cached. JCSWorker
051     * will call this itself! You should not call this directly.
052     * <p>
053     * @return The result of doing the work to be cached.
054     * @throws Exception
055     *             If anything goes wrong while doing the work, an Exception
056     *             should be thrown.
057     */
058    V doWork() throws Exception;
059}