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    
015    package org.apache.tapestry5.ioc;
016    
017    import org.apache.tapestry5.ioc.annotations.EagerLoad;
018    import 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     */
027    public 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    }