Java tutorial
/* * Copyright 2012 The Netty Project * * The Netty Project licenses this file to you under the Apache License, * version 2.0 (the "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at: * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. */ package io.netty.handler.codec.http; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.embedded.EmbeddedChannel; import io.netty.handler.codec.compression.ZlibCodecFactory; import io.netty.handler.codec.compression.ZlibWrapper; /** * Compresses an {@link HttpMessage} and an {@link HttpContent} in {@code gzip} or * {@code deflate} encoding while respecting the {@code "Accept-Encoding"} header. * If there is no matching encoding, no compression is done. For more * information on how this handler modifies the message, please refer to * {@link HttpContentEncoder}. */ public class HttpContentCompressor extends HttpContentEncoder { private final int compressionLevel; private final int windowBits; private final int memLevel; private final int contentSizeThreshold; private ChannelHandlerContext ctx; /** * Creates a new handler with the default compression level (<tt>6</tt>), * default window size (<tt>15</tt>) and default memory level (<tt>8</tt>). */ public HttpContentCompressor() { this(6); } /** * Creates a new handler with the specified compression level, default * window size (<tt>15</tt>) and default memory level (<tt>8</tt>). * * @param compressionLevel * {@code 1} yields the fastest compression and {@code 9} yields the * best compression. {@code 0} means no compression. The default * compression level is {@code 6}. */ public HttpContentCompressor(int compressionLevel) { this(compressionLevel, 15, 8, 0); } /** * Creates a new handler with the specified compression level, window size, * and memory level.. * * @param compressionLevel * {@code 1} yields the fastest compression and {@code 9} yields the * best compression. {@code 0} means no compression. The default * compression level is {@code 6}. * @param windowBits * The base two logarithm of the size of the history buffer. The * value should be in the range {@code 9} to {@code 15} inclusive. * Larger values result in better compression at the expense of * memory usage. The default value is {@code 15}. * @param memLevel * How much memory should be allocated for the internal compression * state. {@code 1} uses minimum memory and {@code 9} uses maximum * memory. Larger values result in better and faster compression * at the expense of memory usage. The default value is {@code 8} */ public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel) { this(compressionLevel, windowBits, memLevel, 0); } /** * Creates a new handler with the specified compression level, window size, * and memory level.. * * @param compressionLevel * {@code 1} yields the fastest compression and {@code 9} yields the * best compression. {@code 0} means no compression. The default * compression level is {@code 6}. * @param windowBits * The base two logarithm of the size of the history buffer. The * value should be in the range {@code 9} to {@code 15} inclusive. * Larger values result in better compression at the expense of * memory usage. The default value is {@code 15}. * @param memLevel * How much memory should be allocated for the internal compression * state. {@code 1} uses minimum memory and {@code 9} uses maximum * memory. Larger values result in better and faster compression * at the expense of memory usage. The default value is {@code 8} * @param contentSizeThreshold * The response body is compressed when the size of the response * body exceeds the threshold. The value should be a non negative * number. {@code 0} will enable compression for all responses. */ public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel, int contentSizeThreshold) { if (compressionLevel < 0 || compressionLevel > 9) { throw new IllegalArgumentException("compressionLevel: " + compressionLevel + " (expected: 0-9)"); } if (windowBits < 9 || windowBits > 15) { throw new IllegalArgumentException("windowBits: " + windowBits + " (expected: 9-15)"); } if (memLevel < 1 || memLevel > 9) { throw new IllegalArgumentException("memLevel: " + memLevel + " (expected: 1-9)"); } if (contentSizeThreshold < 0) { throw new IllegalArgumentException( "contentSizeThreshold: " + contentSizeThreshold + " (expected: non negative number)"); } this.compressionLevel = compressionLevel; this.windowBits = windowBits; this.memLevel = memLevel; this.contentSizeThreshold = contentSizeThreshold; } @Override public void handlerAdded(ChannelHandlerContext ctx) throws Exception { this.ctx = ctx; } @Override protected Result beginEncode(HttpResponse httpResponse, String acceptEncoding) throws Exception { if (this.contentSizeThreshold > 0) { if (httpResponse instanceof HttpContent && ((HttpContent) httpResponse).content().readableBytes() < contentSizeThreshold) { return null; } } String contentEncoding = httpResponse.headers().get(HttpHeaderNames.CONTENT_ENCODING); if (contentEncoding != null) { // Content-Encoding was set, either as something specific or as the IDENTITY encoding // Therefore, we should NOT encode here return null; } ZlibWrapper wrapper = determineWrapper(acceptEncoding); if (wrapper == null) { return null; } String targetContentEncoding; switch (wrapper) { case GZIP: targetContentEncoding = "gzip"; break; case ZLIB: targetContentEncoding = "deflate"; break; default: throw new Error(); } return new Result(targetContentEncoding, new EmbeddedChannel(ctx.channel().id(), ctx.channel().metadata().hasDisconnect(), ctx.channel().config(), ZlibCodecFactory.newZlibEncoder(wrapper, compressionLevel, windowBits, memLevel))); } @SuppressWarnings("FloatingPointEquality") protected ZlibWrapper determineWrapper(String acceptEncoding) { float starQ = -1.0f; float gzipQ = -1.0f; float deflateQ = -1.0f; for (String encoding : acceptEncoding.split(",")) { float q = 1.0f; int equalsPos = encoding.indexOf('='); if (equalsPos != -1) { try { q = Float.parseFloat(encoding.substring(equalsPos + 1)); } catch (NumberFormatException e) { // Ignore encoding q = 0.0f; } } if (encoding.contains("*")) { starQ = q; } else if (encoding.contains("gzip") && q > gzipQ) { gzipQ = q; } else if (encoding.contains("deflate") && q > deflateQ) { deflateQ = q; } } if (gzipQ > 0.0f || deflateQ > 0.0f) { if (gzipQ >= deflateQ) { return ZlibWrapper.GZIP; } else { return ZlibWrapper.ZLIB; } } if (starQ > 0.0f) { if (gzipQ == -1.0f) { return ZlibWrapper.GZIP; } if (deflateQ == -1.0f) { return ZlibWrapper.ZLIB; } } return null; } }