    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.assets;
    014
    015import org.apache.tapestry5.commons.Resource;
    016import org.apache.tapestry5.http.ContentType;
    017
    018import java.io.IOException;
    019import java.io.InputStream;
    020
    021/**
    022 * A transformer is used to read a {@link Resource} and pass it through a transformation stage, to get a
    023 * stream that can be used on the client side. Examples of this are languages that "compile" to
    024 * JavaScript, or any of a few higher-level versions of CSS that are compiled to standard CSS.
    025 * ResourceTransformers are contributed to the {@link StreamableResourceSource} service.
    026 *
    027 * @since 5.3
    028 * @see StreamableResourceSource
    029 */
    030public interface ResourceTransformer
    031{
    032    /**
    033     * Returns the MIME type of a transformed stream.
    034     *
    035     * @since 5.4
    036     */
    037    ContentType getTransformedContentType();
    038
    039    /**
    040     * Read the source input stream and provide a new input stream of the transformed content.
    041     *
    042     * @param source
    043     *         input content
    044     * @param dependencies
    045     *         allows additional dependencies of the source to be tracked
    046     * @return stream of output content
    047     * @throws IOException
    048     */
    049    InputStream transform(Resource source, ResourceDependencies dependencies) throws IOException;
    050}