1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.myfaces.commons.resourcehandler;
20
21
22 /**
23 * Utility methods needed in PackagedResource and PackagedResourceHandler.
24 *
25 * @author Jakob Korherr
26 */
27 public class ResourceUtils
28 {
29 /**
30 * Checks if the user agent supports GZIP compression on basis of the "Accept-Encoding" header field.
31 * Created according to RFC2616, section 14.3 Accept-Encoding.
32 *
33 * Some examples of Accept-Encoding:
34 *
35 * Accept-Encoding: gzip, deflate
36 * Accept-Encoding:
37 * Accept-Encoding: *
38 * Accept-Encoding: compress;q=0.5, gzip;q=1.0
39 * Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
40 *
41 * @param acceptEncodingHeader
42 * @return
43 */
44 public static boolean isGZIPEncodingAccepted(String acceptEncodingHeader)
45 {
46 if (acceptEncodingHeader == null)
47 {
48 return false;
49 }
50 int gzipIndex = acceptEncodingHeader.indexOf("gzip");
51 if (gzipIndex != -1)
52 {
53 // "gzip" appears in the header
54 // --> check if banned via q=0
55 return !isEncodingQValueZero(acceptEncodingHeader, gzipIndex);
56 }
57
58 // no "gzip" in header --> check for "*"
59 int starIndex = acceptEncodingHeader.indexOf('*');
60 if (starIndex != -1)
61 {
62 // "*" appears in the header
63 // --> check if banned via q=0
64 return !isEncodingQValueZero(acceptEncodingHeader, starIndex);
65 }
66
67 // neither "gzip" nor "*" in header
68 return false;
69 }
70
71 private static boolean isEncodingQValueZero(String acceptEncodingHeader, int startIndex)
72 {
73 // remove any precending definitions
74 String encodingSubstring = acceptEncodingHeader.substring(startIndex);
75
76 // remove any subsequent definitions (separated via ,)
77 int commaIndex = encodingSubstring.indexOf(',');
78 if (commaIndex != -1)
79 {
80 encodingSubstring = encodingSubstring.substring(0, commaIndex);
81 }
82
83 int qZeroIndex = encodingSubstring.indexOf("q=0");
84 if (qZeroIndex != -1)
85 {
86 String qZeroSubstring = encodingSubstring.substring(qZeroIndex).trim();
87 if (qZeroSubstring.matches("q=0(\\.(0){0,3})?"))
88 {
89 // "q=0" or "q=0." or "q=0.0" or "q=0.00" or "q=0.000" found
90 // NOTE that there MUST NOT be more than 3 digits after the decimal point (per RFC section 3.9)
91 return true;
92 }
93 else
94 {
95 // q=0.xyz" found with any of xyz being != 0
96 return false;
97 }
98 }
99 else
100 {
101 // "q=0" not found
102 return false;
103 }
104 }
105
106 }