001    // Copyright 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.services.assets;
016    
017    import org.apache.tapestry5.ioc.Resource;
018    
019    import java.io.IOException;
020    import java.io.InputStream;
021    
022    /**
023     * A transformer is used to read a {@link Resource} and pass it through a transformation stage, to get a
024     * stream that can be used on the client side. Examples of this are languages that "compile" to
025     * JavaScript, or any of a few higher-level versions of CSS that are compiled to standard CSS.
026     *
027     * @since 5.3
028     */
029    public interface ResourceTransformer
030    {
031        /**
032         * Read the source input stream and provide a new input stream of the transformed content.
033         *
034         * @param source       input content
035         * @param dependencies allows additional dependencies of the source to be tracked
036         * @return stream of output content
037         * @throws IOException
038         */
039        InputStream transform(Resource source, ResourceDependencies dependencies) throws IOException;
040    }