View Javadoc

    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.buffer.ChannelBuffers;
    20  import org.jboss.netty.channel.ChannelHandlerContext;
    21  import org.jboss.netty.channel.ChannelStateEvent;
    22  import org.jboss.netty.channel.Channels;
    23  import org.jboss.netty.channel.LifeCycleAwareChannelHandler;
    24  import org.jboss.netty.channel.MessageEvent;
    25  import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
    26  import org.jboss.netty.handler.codec.embedder.DecoderEmbedder;
    27
    28  /**
    29   * Decodes the content of the received {@link HttpRequest} and {@link HttpChunk}.
    30   * The original content is replaced with the new content decoded by the
    31   * {@link DecoderEmbedder}, which is created by {@link #newContentDecoder(String)}.
    32   * Once decoding is finished, the value of the <tt>'Content-Encoding'</tt>
    33   * header is set to the target content encoding, as returned by {@link #getTargetContentEncoding(String)}.
    34   * Also, the <tt>'Content-Length'</tt> header is updated to the length of the
    35   * decoded content.  If the content encoding of the original is not supported
    36   * by the decoder, {@link #newContentDecoder(String)} should return {@code null}
    37   * so that no decoding occurs (i.e. pass-through).
    38   * <p>
    39   * Please note that this is an abstract class.  You have to extend this class
    40   * and implement {@link #newContentDecoder(String)} properly to make this class
    41   * functional.  For example, refer to the source code of {@link HttpContentDecompressor}.
    42   * <p>
    43   * This handler must be placed after {@link HttpMessageDecoder} in the pipeline
    44   * so that this handler can intercept HTTP requests after {@link HttpMessageDecoder}
    45   * converts {@link ChannelBuffer}s into HTTP requests.
    46   */
    47  public abstract class HttpContentDecoder extends SimpleChannelUpstreamHandler
    48                                           implements LifeCycleAwareChannelHandler {
    49
    50      private DecoderEmbedder<ChannelBuffer> decoder;
    51
    52      /**
    53       * Creates a new instance.
    54       */
    55      protected HttpContentDecoder() {
    56          super();
    57      }
    58
    59      @Override
    60      public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
    61          Object msg = e.getMessage();
    62          if (msg instanceof HttpResponse && ((HttpResponse) msg).getStatus().getCode() == 100) {
    63              // 100-continue response must be passed through.
    64              ctx.sendUpstream(e);
    65          } else if (msg instanceof HttpMessage) {
    66              HttpMessage m = (HttpMessage) msg;
    67
    68              // Clean-up the previous decoder if not cleaned up correctly.
    69              finishDecode();
    70
    71              // Determine the content encoding.
    72              String contentEncoding = m.getHeader(HttpHeaders.Names.CONTENT_ENCODING);
    73              if (contentEncoding != null) {
    74                  contentEncoding = contentEncoding.trim();
    75              } else {
    76                  contentEncoding = HttpHeaders.Values.IDENTITY;
    77              }
    78
    79              boolean hasContent = m.isChunked() || m.getContent().readable();
    80              if (hasContent && (decoder = newContentDecoder(contentEncoding)) != null) {
    81                  // Decode the content and remove or replace the existing headers
    82                  // so that the message looks like a decoded message.
    83                  m.setHeader(
    84                          HttpHeaders.Names.CONTENT_ENCODING,
    85                          getTargetContentEncoding(contentEncoding));
    86
    87                  if (!m.isChunked()) {
    88                      ChannelBuffer content = m.getContent();
    89                      // Decode the content
    90                      content = ChannelBuffers.wrappedBuffer(
    91                              decode(content), finishDecode());
    92
    93                      // Replace the content.
    94                      m.setContent(content);
    95                      if (m.containsHeader(HttpHeaders.Names.CONTENT_LENGTH)) {
    96                          m.setHeader(
    97                                  HttpHeaders.Names.CONTENT_LENGTH,
    98                                  Integer.toString(content.readableBytes()));
    99                      }
    100                 }
    101             }
    102
    103             // Because HttpMessage is a mutable object, we can simply forward the received event.
    104             ctx.sendUpstream(e);
    105         } else if (msg instanceof HttpChunk) {
    106             HttpChunk c = (HttpChunk) msg;
    107             ChannelBuffer content = c.getContent();
    108
    109             // Decode the chunk if necessary.
    110             if (decoder != null) {
    111                 if (!c.isLast()) {
    112                     content = decode(content);
    113                     if (content.readable()) {
    114                         c.setContent(content);
    115                         ctx.sendUpstream(e);
    116                     }
    117                 } else {
    118                     ChannelBuffer lastProduct = finishDecode();
    119
    120                     // Generate an additional chunk if the decoder produced
    121                     // the last product on closure,
    122                     if (lastProduct.readable()) {
    123                         Channels.fireMessageReceived(
    124                                 ctx, new DefaultHttpChunk(lastProduct), e.getRemoteAddress());
    125                     }
    126
    127                     // Emit the last chunk.
    128                     ctx.sendUpstream(e);
    129                 }
    130             } else {
    131                 ctx.sendUpstream(e);
    132             }
    133         } else {
    134             ctx.sendUpstream(e);
    135         }
    136     }
    137
    138     @Override
    139     public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
    140         // Clean-up the previous decoder if not cleaned up correctly.
    141         finishDecode();
    142
    143         super.channelClosed(ctx, e);
    144     }
    145
    146     /**
    147      * Returns a new {@link DecoderEmbedder} that decodes the HTTP message
    148      * content encoded in the specified <tt>contentEncoding</tt>.
    149      *
    150      * @param contentEncoding the value of the {@code "Content-Encoding"} header
    151      * @return a new {@link DecoderEmbedder} if the specified encoding is supported.
    152      *         {@code null} otherwise (alternatively, you can throw an exception
    153      *         to block unknown encoding).
    154      */
    155     protected abstract DecoderEmbedder<ChannelBuffer> newContentDecoder(String contentEncoding) throws Exception;
    156
    157     /**
    158      * Returns the expected content encoding of the decoded content.
    159      * This method returns {@code "identity"} by default, which is the case for
    160      * most decoders.
    161      *
    162      * @param contentEncoding the value of the {@code "Content-Encoding"} header
    163      * @return the expected content encoding of the new content
    164      */
    165     protected String getTargetContentEncoding(String contentEncoding) throws Exception {
    166         return HttpHeaders.Values.IDENTITY;
    167     }
    168
    169     private ChannelBuffer decode(ChannelBuffer buf) {
    170         decoder.offer(buf);
    171         return ChannelBuffers.wrappedBuffer(decoder.pollAll(new ChannelBuffer[decoder.size()]));
    172     }
    173
    174     private ChannelBuffer finishDecode() {
    175         if (decoder == null) {
    176             return ChannelBuffers.EMPTY_BUFFER;
    177         }
    178
    179         ChannelBuffer result;
    180         if (decoder.finish()) {
    181             result = ChannelBuffers.wrappedBuffer(decoder.pollAll(new ChannelBuffer[decoder.size()]));
    182         } else {
    183             result = ChannelBuffers.EMPTY_BUFFER;
    184         }
    185         decoder = null;
    186         return result;
    187     }
    188
    189     public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
    190         // NOOP
    191     }
    192
    193     public void afterAdd(ChannelHandlerContext ctx) throws Exception {
    194         // NOOP
    195     }
    196
    197     public void beforeRemove(ChannelHandlerContext ctx) throws Exception {
    198         // NOOP
    199     }
    200
    201     public void afterRemove(ChannelHandlerContext ctx) throws Exception {
    202         finishDecode();
    203     }
    204 }