    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.services;
    014
    015import org.apache.tapestry5.Asset;
    016import org.apache.tapestry5.commons.Resource;
    017
    018/**
    019 * Used by {@link AssetSource} to create new {@link Asset}s as needed.
    020 *
    021 * Starting in Tapestry 5.4, the built-in implementations of this interface (for context assets, and for classpath assets)
    022 * were changed so that when underlying resources changed, the client URLs for Assets are discarded; this is necessitated by two factors:
    023 * 1) the {@linkplain org.apache.tapestry5.Asset#toClientURL() client URL}
    024 * for an Asset now includes a checksum based on the content of the underlying resource, so a change to resource content
    025 * (during development) results in a change to the URL.
    026 * 2) {@link org.apache.tapestry5.services.javascript.JavaScriptStack} (especially the {@link org.apache.tapestry5.services.javascript.ExtensibleJavaScriptStack} implementation)
    027 * made no provision for rebuilding the Assets post-construction, and there is no backwards compatible way to
    028 * introduce this concept (and JavaScriptStacks are something many applications and third-party libraries make use of).
    029 * So, starting in Tapestry 5.4, the implementations of {@link Asset} should be
    030 *
    031 * @see org.apache.tapestry5.services.AssetSource
    032 */
    033public interface AssetFactory
    034{
    035    /**
    036     * Returns the Resource representing the root folder of the domain this factory is responsible for.
    037     */
    038    Resource getRootResource();
    039
    040    /**
    041     * Creates an instance of an asset.
    042     *
    043     * @param resource
    044     *         a resource within this factories domain (derived from the {@linkplain #getRootResource() root
    045     *         resource})
    046     * @return an Asset for the resource
    047     */
    048    Asset createAsset(Resource resource);
    049}