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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.HttpEntity;
33  import org.apache.http.HttpEntityEnclosingRequest;
34  import org.apache.http.HttpException;
35  import org.apache.http.HttpRequest;
36  import org.apache.http.HttpRequestInterceptor;
37  import org.apache.http.HttpVersion;
38  import org.apache.http.ProtocolVersion;
39  import org.apache.http.annotation.Immutable;
40  import org.apache.http.params.HttpProtocolParams;
41  
42  /**
43   * RequestExpectContinue is responsible for enabling the 'expect-continue'
44   * handshake by adding <code>Expect</code> header. This interceptor is
45   * recommended for client side protocol processors.
46   * <p>
47   * The following parameters can be used to customize the behavior of this
48   * class:
49   * <ul>
50   *  <li>{@link org.apache.http.params.CoreProtocolPNames#USE_EXPECT_CONTINUE}</li>
51   * </ul>
52   *
53   * @since 4.0
54   */
55  @Immutable
56  public class RequestExpectContinue implements HttpRequestInterceptor {
57  
58      public RequestExpectContinue() {
59          super();
60      }
61  
62      public void process(final HttpRequest request, final HttpContext context)
63              throws HttpException, IOException {
64          if (request == null) {
65              throw new IllegalArgumentException("HTTP request may not be null");
66          }
67          if (request instanceof HttpEntityEnclosingRequest) {
68              HttpEntity entity = ((HttpEntityEnclosingRequest)request).getEntity();
69              // Do not send the expect header if request body is known to be empty
70              if (entity != null && entity.getContentLength() != 0) {
71                  ProtocolVersion ver = request.getRequestLine().getProtocolVersion();
72                  if (HttpProtocolParams.useExpectContinue(request.getParams())
73                          && !ver.lessEquals(HttpVersion.HTTP_1_0)) {
74                      request.addHeader(HTTP.EXPECT_DIRECTIVE, HTTP.EXPECT_CONTINUE);
75                  }
76              }
77          }
78      }
79  
80  }