Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||||||
GzipUtil |
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1 | // Copyright 2004, 2005 The Apache Software Foundation |
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2 | // |
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3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
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4 | // you may not use this file except in compliance with the License. |
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5 | // You may obtain a copy of the License at |
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6 | // |
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7 | // http://www.apache.org/licenses/LICENSE-2.0 |
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8 | // |
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9 | // Unless required by applicable law or agreed to in writing, software |
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10 | // distributed under the License is distributed on an "AS IS" BASIS, |
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11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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12 | // See the License for the specific language governing permissions and |
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13 | // limitations under the License. |
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14 | package org.apache.tapestry.util.io; |
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15 | ||
16 | import org.apache.tapestry.web.WebRequest; |
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17 | ||
18 | ||
19 | /** |
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20 | * Encapsulates logic related to various gzip compression schemes and their rules |
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21 | * as they apply to different browsers. |
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22 | * |
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23 | * @author jkuhnert |
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24 | */ |
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25 | public final class GzipUtil |
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26 | { |
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27 | private static final float MIN_IE_VERSION = 7.0f; |
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28 | ||
29 | private static final String MSIE_6_COMPATIBLE_STRING = "SV1"; |
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30 | ||
31 | /* defeat instantiation */ |
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32 | 0 | private GzipUtil() { } |
33 | ||
34 | /** |
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35 | * Determines if gzip compression is appropriate/possible based on the User Agent and |
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36 | * other limiting factors. IE versions < 6.1 are known to not work with gzip compression reliably. |
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37 | * |
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38 | * @return True, if this request can be served in gzip format. False otherwise. |
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39 | */ |
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40 | public static boolean isGzipCapable(WebRequest request) |
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41 | { |
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42 | 10 | String encoding = request.getHeader("Accept-Encoding"); |
43 | 10 | if (encoding == null || encoding.indexOf("gzip") < 0) |
44 | 0 | return false; |
45 | ||
46 | // Handle IE specific hacks |
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47 | ||
48 | 10 | String userAgent = request.getHeader("User-Agent"); |
49 | 10 | int ieIndex = (userAgent != null) ? userAgent.indexOf("MSIE") : -1; |
50 | 10 | if (ieIndex > -1) { |
51 | ||
52 | 5 | float version = -1; |
53 | ||
54 | try { |
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55 | 5 | version = Float.parseFloat(userAgent.substring(ieIndex + 4, ieIndex + 8)); |
56 | 5 | } catch (NumberFormatException nf) {nf.printStackTrace();} |
57 | ||
58 | 5 | if (version >= MIN_IE_VERSION) |
59 | 1 | return true; |
60 | ||
61 | 4 | if (userAgent.indexOf(MSIE_6_COMPATIBLE_STRING) > -1) |
62 | 1 | return true; |
63 | ||
64 | // else false |
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65 | ||
66 | 3 | return false; |
67 | } |
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68 | ||
69 | 5 | return true; |
70 | } |
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71 | ||
72 | /** |
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73 | * Based on the given type of content, determines if compression is appropriate. The biggest |
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74 | * thing it does is make sure that image content isn't compressed as that kind of content |
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75 | * is already compressed fairly well. |
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76 | * |
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77 | * @param contentType |
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78 | * The content type to check. (ie "text/javascript","text/html", etc..) |
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79 | * |
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80 | * @return True if compression is appropriate for the content specified, false otherwise. |
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81 | */ |
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82 | public static boolean shouldCompressContentType(String contentType) |
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83 | { |
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84 | 8 | if (contentType == null) |
85 | 1 | return false; |
86 | ||
87 | 7 | return contentType.indexOf("javascript") > -1 |
88 | || contentType.indexOf("css") > -1 |
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89 | || contentType.indexOf("html") > -1 |
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90 | || contentType.indexOf("text") > -1; |
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91 | } |
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92 | } |