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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.codec.http;
17  
18  import io.netty.buffer.ByteBuf;
19  import io.netty.channel.ChannelPipeline;
20  import io.netty.handler.codec.TooLongFrameException;
21  
22  
23  /**
24   * Decodes {@link ByteBuf}s into {@link HttpResponse}s and
25   * {@link HttpContent}s.
26   *
27   * <h3>Parameters that prevents excessive memory consumption</h3>
28   * <table border="1">
29   * <tr>
30   * <th>Name</th><th>Meaning</th>
31   * </tr>
32   * <tr>
33   * <td>{@code maxInitialLineLength}</td>
34   * <td>The maximum length of the initial line (e.g. {@code "HTTP/1.0 200 OK"})
35   *     If the length of the initial line exceeds this value, a
36   *     {@link TooLongFrameException} will be raised.</td>
37   * </tr>
38   * <tr>
39   * <td>{@code maxHeaderSize}</td>
40   * <td>The maximum length of all headers.  If the sum of the length of each
41   *     header exceeds this value, a {@link TooLongFrameException} will be raised.</td>
42   * </tr>
43   * <tr>
44   * <td>{@code maxChunkSize}</td>
45   * <td>The maximum length of the content or each chunk.  If the content length
46   *     exceeds this value, the transfer encoding of the decoded response will be
47   *     converted to 'chunked' and the content will be split into multiple
48   *     {@link HttpContent}s.  If the transfer encoding of the HTTP response is
49   *     'chunked' already, each chunk will be split into smaller chunks if the
50   *     length of the chunk exceeds this value.  If you prefer not to handle
51   *     {@link HttpContent}s in your handler, insert {@link HttpObjectAggregator}
52   *     after this decoder in the {@link ChannelPipeline}.</td>
53   * </tr>
54   * </table>
55   *
56   * <h3>Decoding a response for a <tt>HEAD</tt> request</h3>
57   * <p>
58   * Unlike other HTTP requests, the successful response of a <tt>HEAD</tt>
59   * request does not have any content even if there is <tt>Content-Length</tt>
60   * header.  Because {@link HttpResponseDecoder} is not able to determine if the
61   * response currently being decoded is associated with a <tt>HEAD</tt> request,
62   * you must override {@link #isContentAlwaysEmpty(HttpMessage)} to return
63   * <tt>true</tt> for the response of the <tt>HEAD</tt> request.
64   * </p><p>
65   * If you are writing an HTTP client that issues a <tt>HEAD</tt> request,
66   * please use {@link HttpClientCodec} instead of this decoder.  It will perform
67   * additional state management to handle the responses for <tt>HEAD</tt>
68   * requests correctly.
69   * </p>
70   *
71   * <h3>Decoding a response for a <tt>CONNECT</tt> request</h3>
72   * <p>
73   * You also need to do additional state management to handle the response of a
74   * <tt>CONNECT</tt> request properly, like you did for <tt>HEAD</tt>.  One
75   * difference is that the decoder should stop decoding completely after decoding
76   * the successful 200 response since the connection is not an HTTP connection
77   * anymore.
78   * </p><p>
79   * {@link HttpClientCodec} also handles this edge case correctly, so you have to
80   * use {@link HttpClientCodec} if you are writing an HTTP client that issues a
81   * <tt>CONNECT</tt> request.
82   * </p>
83   */
84  public class HttpResponseDecoder extends HttpObjectDecoder {
85  
86      private static final HttpResponseStatus UNKNOWN_STATUS = new HttpResponseStatus(999, "Unknown");
87  
88      /**
89       * Creates a new instance with the default
90       * {@code maxInitialLineLength (4096)}, {@code maxHeaderSize (8192)}, and
91       * {@code maxChunkSize (8192)}.
92       */
93      public HttpResponseDecoder() {
94      }
95  
96      /**
97       * Creates a new instance with the specified parameters.
98       */
99      public HttpResponseDecoder(
100             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) {
101         super(maxInitialLineLength, maxHeaderSize, maxChunkSize, true);
102     }
103 
104     public HttpResponseDecoder(
105             int maxInitialLineLength, int maxHeaderSize, int maxChunkSize, boolean validateHeaders) {
106         super(maxInitialLineLength, maxHeaderSize, maxChunkSize, true, validateHeaders);
107     }
108 
109     @Override
110     protected HttpMessage createMessage(String[] initialLine) {
111         return new DefaultHttpResponse(
112                 HttpVersion.valueOf(initialLine[0]),
113                 new HttpResponseStatus(Integer.parseInt(initialLine[1]), initialLine[2]), validateHeaders);
114     }
115 
116     @Override
117     protected HttpMessage createInvalidMessage() {
118         return new DefaultFullHttpResponse(HttpVersion.HTTP_1_0, UNKNOWN_STATUS, validateHeaders);
119     }
120 
121     @Override
122     protected boolean isDecodingRequest() {
123         return false;
124     }
125 }