001// Copyright 2011, 2012 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.services.assets;
016
017import org.apache.tapestry5.commons.Resource;
018import org.apache.tapestry5.http.ContentType;
019import org.apache.tapestry5.ioc.annotations.UsesMappedConfiguration;
020
021import java.io.IOException;
022import java.util.Set;
023
024/**
025 * Converts {@link Resource}s into {@link StreamableResource}s, and may be responsible for
026 * {@linkplain ResourceTransformer transforming} resources based on file extension. Contributions map a file extension
027 * (such as "coffee") to a transformer for that file extension.
028 * Service decorators added to this service may provide additional processing (compression, minimization, and caching).
029 *
030 * @since 5.3
031 */
032@UsesMappedConfiguration(ResourceTransformer.class)
033public interface StreamableResourceSource
034{
035    /**
036     * Given a desired content type, identify which file extensions can be mapped to that extension based on
037     * contributed {@link ResourceTransformer}s that can
038     * {@linkplain org.apache.tapestry5.services.assets.ResourceTransformer#getTransformedContentType() produce the content type}
039     * based for a file with that extension.
040     *
041     * @param contentType
042     *         to search for (just a MIME type, such as "text/javascript")
043     * @return set of file extension, possibly empty, in no particular order. These are the bare extensions, e.g.,
044     * "js", "coffee".
045     * @since 5.4
046     */
047    Set<String> fileExtensionsForContentType(ContentType contentType);
048
049    /**
050     * Converts a Resource (which must be non-null and exist) into a streamable resource, along with
051     * some additional optional behaviors.
052     *
053     * @param baseResource
054     *         the resource to convert
055     * @param processing
056     *         defines additional processing after the resource has been read and possibly transformed
057     * @param dependencies
058     *         Passed to any {@link ResourceTransformer} to track additional dependencies of the base resource
059     * @return the contents of the Resource, possibly transformed, in a streamable format.
060     * @throws IOException
061     *         if the resource does not exist or a URL for the content is not available
062     */
063    StreamableResource getStreamableResource(Resource baseResource, StreamableResourceProcessing processing, ResourceDependencies dependencies)
064            throws IOException;
065}