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.internal.services.assets;
016    
017    import org.apache.tapestry5.ioc.Resource;
018    import org.apache.tapestry5.services.assets.*;
019    
020    import java.io.BufferedOutputStream;
021    import java.io.ByteArrayOutputStream;
022    import java.io.IOException;
023    import java.util.zip.GZIPOutputStream;
024    
025    public class SRSCompressingInterceptor implements StreamableResourceSource
026    {
027        private final int compressionCutoff;
028    
029        private final StreamableResourceSource delegate;
030    
031        public SRSCompressingInterceptor(int compressionCutoff, StreamableResourceSource delegate)
032        {
033            this.compressionCutoff = compressionCutoff;
034            this.delegate = delegate;
035        }
036    
037        public StreamableResource getStreamableResource(Resource baseResource, StreamableResourceProcessing processing, ResourceDependencies dependencies)
038                throws IOException
039        {
040            StreamableResource streamable = delegate.getStreamableResource(baseResource, processing, dependencies);
041    
042            return processing == StreamableResourceProcessing.COMPRESSION_ENABLED ? compress(streamable) : streamable;
043        }
044    
045        private StreamableResource compress(StreamableResource uncompressed) throws IOException
046        {
047            if (uncompressed.getCompression() != CompressionStatus.COMPRESSABLE)
048            {
049                return uncompressed;
050            }
051    
052            int size = uncompressed.getSize();
053    
054            // Because of GZIP overhead, streams below a certain point actually get larger when compressed so
055            // we don't even try.
056    
057            if (size < compressionCutoff)
058            {
059                return uncompressed;
060            }
061    
062            ByteArrayOutputStream bos = new ByteArrayOutputStream(size);
063    
064            GZIPOutputStream gos = new GZIPOutputStream(bos);
065            BufferedOutputStream buffered = new BufferedOutputStream(gos);
066    
067            uncompressed.streamTo(buffered);
068    
069            buffered.close();
070    
071            BytestreamCache cache = new BytestreamCache(bos);
072    
073            return new StreamableResourceImpl(uncompressed.getDescription(),
074                    uncompressed.getContentType(), CompressionStatus.COMPRESSED,
075                    uncompressed.getLastModified(), cache);
076        }
077    }