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1   /*
2    * ====================================================================
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *   http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing,
14   * software distributed under the License is distributed on an
15   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16   * KIND, either express or implied.  See the License for the
17   * specific language governing permissions and limitations
18   * under the License.
19   * ====================================================================
20   *
21   * This software consists of voluntary contributions made by many
22   * individuals on behalf of the Apache Software Foundation.  For more
23   * information on the Apache Software Foundation, please see
24   * <http://www.apache.org/>.
25   *
26   */
27  package org.apache.http.client.protocol;
28  
29  import java.io.IOException;
30  import java.util.List;
31  
32  import org.apache.http.HttpException;
33  import org.apache.http.HttpRequest;
34  import org.apache.http.HttpRequestInterceptor;
35  import org.apache.http.annotation.Immutable;
36  import org.apache.http.protocol.HttpContext;
37  
38  /**
39   * Class responsible for handling Content Encoding requests in HTTP.
40   * <p>
41   * Instances of this class are stateless, therefore they're thread-safe and immutable.
42   *
43   * @see "http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.5"
44   *
45   * @since 4.1
46   */
47  @Immutable
48  public class RequestAcceptEncoding implements HttpRequestInterceptor {
49  
50      private final String acceptEncoding;
51  
52      /**
53       * @since 4.4
54       */
55      public RequestAcceptEncoding(final List<String> encodings) {
56          if (encodings != null && !encodings.isEmpty()) {
57              final StringBuilder buf = new StringBuilder();
58              for (int i = 0; i < encodings.size(); i++) {
59                  if (i > 0) {
60                      buf.append(",");
61                  }
62                  buf.append(encodings.get(i));
63              }
64              this.acceptEncoding = buf.toString();
65          } else {
66              this.acceptEncoding = "gzip,deflate";
67          }
68      }
69  
70      public RequestAcceptEncoding() {
71          this(null);
72      }
73  
74      @Override
75      public void process(
76              final HttpRequest request,
77              final HttpContext context) throws HttpException, IOException {
78  
79          /* Signal support for Accept-Encoding transfer encodings. */
80          if (!request.containsHeader("Accept-Encoding")) {
81              request.addHeader("Accept-Encoding", acceptEncoding);
82          }
83      }
84  
85  }