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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.ThreadingBehavior;
41  import org.apache.http.annotation.Contract;
42  import org.apache.http.util.Args;
43  
44  /**
45   * ResponseContent is the most important interceptor for outgoing responses.
46   * It is responsible for delimiting content length by adding
47   * {@code Content-Length} or {@code Transfer-Content} headers based
48   * on the properties of the enclosed entity and the protocol version.
49   * This interceptor is required for correct functioning of server side protocol
50   * processors.
51   *
52   * @since 4.0
53   */
54  @Contract(threading = ThreadingBehavior.IMMUTABLE)
55  public class ResponseContent implements HttpResponseInterceptor {
56  
57      private final boolean overwrite;
58  
59      /**
60       * Default constructor. The {@code Content-Length} or {@code Transfer-Encoding}
61       * will cause the interceptor to throw {@link ProtocolException} if already present in the
62       * response message.
63       */
64      public ResponseContent() {
65          this(false);
66      }
67  
68      /**
69       * Constructor that can be used to fine-tune behavior of this interceptor.
70       *
71       * @param overwrite If set to {@code true} the {@code Content-Length} and
72       * {@code Transfer-Encoding} headers will be created or updated if already present.
73       * If set to {@code false} the {@code Content-Length} and
74       * {@code Transfer-Encoding} headers will cause the interceptor to throw
75       * {@link ProtocolException} if already present in the response message.
76       *
77       * @since 4.2
78       */
79       public ResponseContent(final boolean overwrite) {
80           super();
81           this.overwrite = overwrite;
82      }
83  
84      /**
85       * Processes the response (possibly updating or inserting) Content-Length and Transfer-Encoding headers.
86       * @param response The HttpResponse to modify.
87       * @param context Unused.
88       * @throws ProtocolException If either the Content-Length or Transfer-Encoding headers are found.
89       * @throws IllegalArgumentException If the response is null.
90       */
91      @Override
92      public void process(final HttpResponse response, final HttpContext context)
93              throws HttpException, IOException {
94          Args.notNull(response, "HTTP response");
95          if (this.overwrite) {
96              response.removeHeaders(HTTP.TRANSFER_ENCODING);
97              response.removeHeaders(HTTP.CONTENT_LEN);
98          } else {
99              if (response.containsHeader(HTTP.TRANSFER_ENCODING)) {
100                 throw new ProtocolException("Transfer-encoding header already present");
101             }
102             if (response.containsHeader(HTTP.CONTENT_LEN)) {
103                 throw new ProtocolException("Content-Length header already present");
104             }
105         }
106         final ProtocolVersion ver = response.getStatusLine().getProtocolVersion();
107         final HttpEntity entity = response.getEntity();
108         if (entity != null) {
109             final long len = entity.getContentLength();
110             if (entity.isChunked() && !ver.lessEquals(HttpVersion.HTTP_1_0)) {
111                 response.addHeader(HTTP.TRANSFER_ENCODING, HTTP.CHUNK_CODING);
112             } else if (len >= 0) {
113                 response.addHeader(HTTP.CONTENT_LEN, Long.toString(entity.getContentLength()));
114             }
115             // Specify a content type if known
116             if (entity.getContentType() != null && !response.containsHeader(
117                     HTTP.CONTENT_TYPE )) {
118                 response.addHeader(entity.getContentType());
119             }
120             // Specify a content encoding if known
121             if (entity.getContentEncoding() != null && !response.containsHeader(
122                     HTTP.CONTENT_ENCODING)) {
123                 response.addHeader(entity.getContentEncoding());
124             }
125         } else {
126             final int status = response.getStatusLine().getStatusCode();
127             if (status != HttpStatus.SC_NO_CONTENT
128                     && status != HttpStatus.SC_NOT_MODIFIED
129                     && status != HttpStatus.SC_RESET_CONTENT) {
130                 response.addHeader(HTTP.CONTENT_LEN, "0");
131             }
132         }
133     }
134 
135 }