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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.ThreadingBehavior;
36  import org.apache.http.annotation.Contract;
37  import org.apache.http.params.CoreProtocolPNames;
38  import org.apache.http.params.HttpParams;
39  import org.apache.http.util.Args;
40  
41  /**
42   * RequestUserAgent is responsible for adding {@code User-Agent} header.
43   * This interceptor is recommended for client side protocol processors.
44   *
45   * @since 4.0
46   */
47  @SuppressWarnings("deprecation")
48  @Contract(threading = ThreadingBehavior.IMMUTABLE)
49  public class RequestUserAgent implements HttpRequestInterceptor {
50  
51      private final String userAgent;
52  
53      public RequestUserAgent(final String userAgent) {
54          super();
55          this.userAgent = userAgent;
56      }
57  
58      public RequestUserAgent() {
59          this(null);
60      }
61  
62      @Override
63      public void process(final HttpRequest request, final HttpContext context)
64          throws HttpException, IOException {
65          Args.notNull(request, "HTTP request");
66          if (!request.containsHeader(HTTP.USER_AGENT)) {
67              String s = null;
68              final HttpParams params = request.getParams();
69              if (params != null) {
70                  s = (String) params.getParameter(CoreProtocolPNames.USER_AGENT);
71              }
72              if (s == null) {
73                  s = this.userAgent;
74              }
75              if (s != null) {
76                  request.addHeader(HTTP.USER_AGENT, s);
77              }
78          }
79      }
80  
81  }