    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
    015package org.apache.tapestry5.internal.services;
    016
    017import org.apache.tapestry5.internal.parser.ComponentTemplate;
    018import org.apache.tapestry5.model.ComponentModel;
    019import org.apache.tapestry5.services.InvalidationEventHub;
    020import 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 */
    030public 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}