    001// Copyright 2011-2013 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.internal.services.assets;
    016
    017import org.apache.tapestry5.commons.Resource;
    018import org.apache.tapestry5.services.assets.*;
    019
    020import java.io.IOException;
    021
    022public class SRSCompressingInterceptor extends DelegatingSRS
    023{
    024    private final int compressionCutoff;
    025
    026    private final AssetChecksumGenerator checksumGenerator;
    027
    028    public SRSCompressingInterceptor(StreamableResourceSource delegate, int compressionCutoff, AssetChecksumGenerator checksumGenerator)
    029    {
    030        super(delegate);
    031        this.compressionCutoff = compressionCutoff;
    032        this.checksumGenerator = checksumGenerator;
    033    }
    034
    035    public StreamableResource getStreamableResource(Resource baseResource, StreamableResourceProcessing processing, ResourceDependencies dependencies)
    036            throws IOException
    037    {
    038        StreamableResource streamable = delegate.getStreamableResource(baseResource, processing, dependencies);
    039
    040        return processing == StreamableResourceProcessing.COMPRESSION_ENABLED ? compress(streamable) : streamable;
    041    }
    042
    043    private StreamableResource compress(StreamableResource uncompressed) throws IOException
    044    {
    045        if (uncompressed.getCompression() != CompressionStatus.COMPRESSABLE)
    046        {
    047            return uncompressed;
    048        }
    049
    050        int size = uncompressed.getSize();
    051
    052        // Because of GZIP overhead, streams below a certain point actually get larger when compressed so
    053        // we don't even try.
    054
    055        if (size < compressionCutoff)
    056        {
    057            return uncompressed;
    058        }
    059
    060        return new CompressedStreamableResource(uncompressed, checksumGenerator);
    061    }
    062}