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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.HttpException;
34  import org.apache.http.HttpResponse;
35  import org.apache.http.HttpResponseInterceptor;
36  import org.apache.http.HttpStatus;
37  import org.apache.http.HttpVersion;
38  import org.apache.http.ProtocolException;
39  import org.apache.http.ProtocolVersion;
40  import org.apache.http.annotation.Immutable;
41  import org.apache.http.util.Args;
42  
43  /**
44   * ResponseContent is the most important interceptor for outgoing responses.
45   * It is responsible for delimiting content length by adding
46   * {@code Content-Length} or {@code Transfer-Content} headers based
47   * on the properties of the enclosed entity and the protocol version.
48   * This interceptor is required for correct functioning of server side protocol
49   * processors.
50   *
51   * @since 4.0
52   */
53  @Immutable
54  public class ResponseContent implements HttpResponseInterceptor {
55  
56      private final boolean overwrite;
57  
58      /**
59       * Default constructor. The {@code Content-Length} or {@code Transfer-Encoding}
60       * will cause the interceptor to throw {@link ProtocolException} if already present in the
61       * response message.
62       */
63      public ResponseContent() {
64          this(false);
65      }
66  
67      /**
68       * Constructor that can be used to fine-tune behavior of this interceptor.
69       *
70       * @param overwrite If set to {@code true} the {@code Content-Length} and
71       * {@code Transfer-Encoding} headers will be created or updated if already present.
72       * If set to {@code false} the {@code Content-Length} and
73       * {@code Transfer-Encoding} headers will cause the interceptor to throw
74       * {@link ProtocolException} if already present in the response message.
75       *
76       * @since 4.2
77       */
78       public ResponseContent(final boolean overwrite) {
79           super();
80           this.overwrite = overwrite;
81      }
82  
83      /**
84       * Processes the response (possibly updating or inserting) Content-Length and Transfer-Encoding headers.
85       * @param response The HttpResponse to modify.
86       * @param context Unused.
87       * @throws ProtocolException If either the Content-Length or Transfer-Encoding headers are found.
88       * @throws IllegalArgumentException If the response is null.
89       */
90      @Override
91      public void process(final HttpResponse response, final HttpContext context)
92              throws HttpException, IOException {
93          Args.notNull(response, "HTTP response");
94          if (this.overwrite) {
95              response.removeHeaders(HTTP.TRANSFER_ENCODING);
96              response.removeHeaders(HTTP.CONTENT_LEN);
97          } else {
98              if (response.containsHeader(HTTP.TRANSFER_ENCODING)) {
99                  throw new ProtocolException("Transfer-encoding header already present");
100             }
101             if (response.containsHeader(HTTP.CONTENT_LEN)) {
102                 throw new ProtocolException("Content-Length header already present");
103             }
104         }
105         final ProtocolVersion ver = response.getStatusLine().getProtocolVersion();
106         final HttpEntity entity = response.getEntity();
107         if (entity != null) {
108             final long len = entity.getContentLength();
109             if (entity.isChunked() && !ver.lessEquals(HttpVersion.HTTP_1_0)) {
110                 response.addHeader(HTTP.TRANSFER_ENCODING, HTTP.CHUNK_CODING);
111             } else if (len >= 0) {
112                 response.addHeader(HTTP.CONTENT_LEN, Long.toString(entity.getContentLength()));
113             }
114             // Specify a content type if known
115             if (entity.getContentType() != null && !response.containsHeader(
116                     HTTP.CONTENT_TYPE )) {
117                 response.addHeader(entity.getContentType());
118             }
119             // Specify a content encoding if known
120             if (entity.getContentEncoding() != null && !response.containsHeader(
121                     HTTP.CONTENT_ENCODING)) {
122                 response.addHeader(entity.getContentEncoding());
123             }
124         } else {
125             final int status = response.getStatusLine().getStatusCode();
126             if (status != HttpStatus.SC_NO_CONTENT
127                     && status != HttpStatus.SC_NOT_MODIFIED
128                     && status != HttpStatus.SC_RESET_CONTENT) {
129                 response.addHeader(HTTP.CONTENT_LEN, "0");
130             }
131         }
132     }
133 
134 }