Forward-port the pull request #172 to fix #164

codec-http/src/main/java/io/netty/handler/codec/http/HttpContentCompressor.java

@@ -123,13 +123,43 @@ public class HttpContentCompressor extends HttpContentEncoder {
                         new ZlibEncoder(wrapper, compressionLevel, windowBits, memLevel)));
     }
 
-    private ZlibWrapper determineWrapper(String acceptEncoding) {
-        // FIXME: Use the Q value.
-        if (acceptEncoding.indexOf("gzip") >= 0) {
-            return ZlibWrapper.GZIP;
+    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.valueOf(encoding.substring(equalsPos + 1));
+                } catch (NumberFormatException e) {
+                    // Ignore encoding
+                    q = 0.0f;
+                }
+            }
+            if (encoding.indexOf("*") >= 0) {
+                starQ = q;
+            } else if (encoding.indexOf("gzip") >= 0 && q > gzipQ) {
+                gzipQ = q;
+            } else if (encoding.indexOf("deflate") >= 0 && q > deflateQ) {
+                deflateQ = q;
+            }
         }
-        if (acceptEncoding.indexOf("deflate") >= 0) {
-            return ZlibWrapper.ZLIB;
+        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;
     }

codec-http/src/test/java/io/netty/handler/codec/http/HttpContentCompressorTest.java

@@ -0,0 +1,62 @@
+/*
+* Copyright 2011 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 org.junit.Assert;
+import org.junit.Test;
+
+import io.netty.handler.codec.compression.ZlibWrapper;
+
+public class HttpContentCompressorTest {
+    @Test
+    public void testGetTargetContentEncoding() throws Exception {
+        HttpContentCompressor compressor = new HttpContentCompressor();
+
+        String[] tests = {
+            // Accept-Encoding -> Content-Encoding
+            "", null,
+            "*", "gzip",
+            "*;q=0.0", null,
+            "gzip", "gzip",
+            "compress, gzip;q=0.5", "gzip",
+            "gzip; q=0.5, identity", "gzip",
+            "gzip ; q=0.1", "gzip",
+            "gzip; q=0, deflate", "deflate",
+            " defalte ; q=0 , *;q=0.5", "gzip",
+        };
+        for (int i = 0; i < tests.length; i += 2) {
+            String acceptEncoding = tests[i];
+            String contentEncoding = tests[i + 1];
+            ZlibWrapper targetWrapper = compressor.determineWrapper(acceptEncoding);
+            String targetEncoding = null;
+            if (targetWrapper != null) {
+                switch (targetWrapper) {
+                case GZIP:
+                    targetEncoding = "gzip";
+                    break;
+                case ZLIB:
+                    targetEncoding = "deflate";
+                    break;
+                default:
+                    if (targetWrapper != null) {
+                        Assert.fail();
+                    }
+                }
+            }
+            Assert.assertEquals(contentEncoding, targetEncoding);
+        }
+    }
+}