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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 org.jboss.netty.handler.codec.http;
    17
    18  import org.jboss.netty.buffer.ChannelBuffer;
    19  import org.jboss.netty.channel.ChannelPipeline;
    20  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
    21
    22
    23  /**
    24   * Decodes {@link ChannelBuffer}s into {@link HttpResponse}s and
    25   * {@link HttpChunk}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 HttpChunk}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 HttpChunk}s in your handler, insert {@link HttpChunkAggregator}
    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 HttpMessageDecoder {
    85
    86      /**
    87       * Creates a new instance with the default
    88       * {@code maxInitialLineLength (4096}}, {@code maxHeaderSize (8192)}, and
    89       * {@code maxChunkSize (8192)}.
    90       */
    91      public HttpResponseDecoder() {
    92          super();
    93      }
    94
    95      /**
    96       * Creates a new instance with the specified parameters.
    97       */
    98      public HttpResponseDecoder(
    99              int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) {
    100         super(maxInitialLineLength, maxHeaderSize, maxChunkSize);
    101     }
    102
    103     @Override
    104     protected HttpMessage createMessage(String[] initialLine) {
    105         return new DefaultHttpResponse(
    106                 HttpVersion.valueOf(initialLine[0]),
    107                 new HttpResponseStatus(Integer.valueOf(initialLine[1]), initialLine[2]));
    108     }
    109
    110     @Override
    111     protected boolean isDecodingRequest() {
    112         return false;
    113     }
    114 }