    001    // Copyright 2006, 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.internal.services;
    016
    017    import org.apache.tapestry5.internal.parser.ComponentTemplate;
    018    import org.apache.tapestry5.model.ComponentModel;
    019    import org.apache.tapestry5.services.InvalidationEventHub;
    020    import org.apache.tapestry5.services.pageload.ComponentResourceSelector;
    021
    022    /**
    023     * Provides access to cached {@link org.apache.tapestry5.internal.parser.ComponentTemplate}s. The source acts as a
    024     * invalidation event hub, and will broadcast invalidation events when any loaded template resource changes. The
    025     * listener for these invalidation events is the page source, which stores cached page instances.
    026     * <p/>
    027     * Any search for a template will end with success (a non-null template), but the template returned may be the
    028     * {@link ComponentTemplate#isMissing() missing template}.
    029     */
    030    public interface ComponentTemplateSource
    031    {
    032        /**
    033         * Provides access to a template. The template will be parsed as necessary. If no template for the exact component
    034         * is found, then the template for the component's parent is returned. In this way, it is possible for a component
    035         * to extend the behavior of its super-class without duplicating the super-class component's template.
    036         * <p/>
    037         * In some cases, the empty template will be returned.
    038         *
    039         * @param componentModel
    040         *            model for the component whose template is to be accessed
    041         * @param selector
    042         *            defines locale and other information needed to locate template
    043         * @return the cached template instance
    044         */
    045        ComponentTemplate getTemplate(ComponentModel componentModel, ComponentResourceSelector selector);
    046
    047        /**
    048         * Event hub used to notify listeners that underlying component template files have changed.
    049         *
    050         * @see org.apache.tapestry5.services.ComponentTemplates
    051         * @since 5.1.0.0
    052         */
    053        InvalidationEventHub getInvalidationEventHub();
    054    }