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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  
28  package org.apache.http.protocol;
29  
30  import java.io.IOException;
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.params.CoreProtocolPNames;
37  import org.apache.http.params.HttpParams;
38  import org.apache.http.util.Args;
39  
40  /**
41   * RequestUserAgent is responsible for adding <code>User-Agent</code> header.
42   * This interceptor is recommended for client side protocol processors.
43   *
44   * @since 4.0
45   */
46  @SuppressWarnings("deprecation")
47  @Immutable
48  public class RequestUserAgent implements HttpRequestInterceptor {
49  
50      private final String userAgent;
51  
52      public RequestUserAgent(final String userAgent) {
53          super();
54          this.userAgent = userAgent;
55      }
56  
57      public RequestUserAgent() {
58          this(null);
59      }
60  
61      public void process(final HttpRequest request, final HttpContext context)
62          throws HttpException, IOException {
63          Args.notNull(request, "HTTP request");
64          if (!request.containsHeader(HTTP.USER_AGENT)) {
65              String s = null;
66              final HttpParams params = request.getParams();
67              if (params != null) {
68                  s = (String) params.getParameter(CoreProtocolPNames.USER_AGENT);
69              }
70              if (s == null) {
71                  s = this.userAgent;
72              }
73              if (s != null) {
74                  request.addHeader(HTTP.USER_AGENT, s);
75              }
76          }
77      }
78  
79  }