001    // Copyright 2006, 2007, 2008, 2011 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.services;
016    
017    /**
018     * An object which manages a list of {@link org.apache.tapestry5.services.InvalidationListener}s. There are multiple
019     * event hub services implementing this interface, each with a specific marker annotation; each can register listeners
020     * and fire events; these are based on the type of resource that has been invalidated. Tapestry has built-in support
021     * for:
022     * <dl>
023     * <dt>message catalog resources
024     * <dd>{@link org.apache.tapestry5.services.ComponentMessages} marker annotation
025     * <dt>component templates
026     * <dd>{@link org.apache.tapestry5.services.ComponentTemplates} marker annotation
027     * <dt>component classes
028     * <dd>{@link org.apache.tapestry5.services.ComponentClasses} marker annotation
029     * </dl>
030     * <p>
031     * Starting in Tapestry 5.3, these services are disabled in production (it does nothing).
032     * 
033     * @since 5.1.0.0
034     */
035    public interface InvalidationEventHub
036    {
037        /**
038         * Adds a listener, who needs to know when an underlying resource of a given category has changed (so that the
039         * receiver may discard any cached data that may have been invalidated). Does nothing in production mode.
040         */
041        void addInvalidationListener(InvalidationListener listener);
042    }