001// Copyright 2010 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.ioc;
016
017import org.apache.tapestry5.ioc.annotations.EagerLoad;
018import org.apache.tapestry5.services.UpdateListenerHub;
019
020/**
021 * Optional interface that may be implemented by a service implementation (or even
022 * a {@linkplain ObjectLocator#proxy(Class, Class) proxy} to give the service implementation
023 * more control over its lifecyle.
024 * 
025 * @since 5.2.2
026 */
027public interface ReloadAware
028{
029    /**
030     * Invoked when Tapestry {@linkplain UpdateListenerHub#fireCheckForUpdates() notices
031     * that the implementation class has changed}. The existing instance is notified, so that
032     * it can cleanly shutdown now, before being re-instantiated. This is necessary when the
033     * service implementation retains some form of external resources.
034     * <p>
035     * In addition, the implementation may request an immediate reload. Normally, reloading of the service is deferred
036     * until a method of the proxy object is invoked (this causes the normal just-in-time instantiation of the
037     * implementation). When this method returns true, the implementation is re-created immediately. This is most often
038     * the case for services that are {@linkplain EagerLoad eagerly loaded} in the first place.
039     * 
040     * @return true if the service should be reloaded immediately, false if reload should be deferred
041     */
042    boolean shutdownImplementationForReload();
043}