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    1   /*
    2    * Copyright 2009 Red Hat, Inc.
    3    *
    4    * Red Hat licenses this file to you under the Apache License, version 2.0
    5    * (the "License"); you may not use this file except in compliance with the
    6    * 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.protobuf;
    17
    18  import static org.jboss.netty.buffer.ChannelBuffers.*;
    19
    20  import org.jboss.netty.buffer.ChannelBuffer;
    21  import org.jboss.netty.channel.Channel;
    22  import org.jboss.netty.channel.ChannelHandlerContext;
    23  import org.jboss.netty.channel.ChannelPipeline;
    24  import org.jboss.netty.channel.MessageEvent;
    25  import org.jboss.netty.channel.ChannelHandler.Sharable;
    26  import org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
    27  import org.jboss.netty.handler.codec.frame.LengthFieldPrepender;
    28  import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
    29
    30  import com.google.protobuf.Message;
    31  import com.google.protobuf.MessageLite;
    32
    33  /**
    34   * Encodes the requested <a href="http://code.google.com/p/protobuf/">Google
    35   * Protocol Buffers</a> {@link Message} and {@link MessageLite} into a
    36   * {@link ChannelBuffer}. A typical setup for TCP/IP would be:
    37   * <pre>
    38   * {@link ChannelPipeline} pipeline = ...;
    39   *
    40   * // Decoders
    41   * pipeline.addLast("frameDecoder",
    42   *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
    43   * pipeline.addLast("protobufDecoder",
    44   *                  new {@link ProtobufDecoder}(MyMessage.getDefaultInstance()));
    45   *
    46   * // Encoder
    47   * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
    48   * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}());
    49   * </pre>
    50   * and then you can use a {@code MyMessage} instead of a {@link ChannelBuffer}
    51   * as a message:
    52   * <pre>
    53   * void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
    54   *     MyMessage req = (MyMessage) e.getMessage();
    55   *     MyMessage res = MyMessage.newBuilder().setText(
    56   *                               "Did you say '" + req.getText() + "'?").build();
    57   *     ch.write(res);
    58   * }
    59   * </pre>
    60   *
    61   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    62   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    63   *
    64   * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
    65   *
    66   * @apiviz.landmark
    67   */
    68  @Sharable
    69  public class ProtobufEncoder extends OneToOneEncoder {
    70
    71      /**
    72       * Creates a new instance.
    73       */
    74      public ProtobufEncoder() {
    75          super();
    76      }
    77
    78      @Override
    79      protected Object encode(
    80              ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
    81          if (!(msg instanceof MessageLite)) {
    82              return msg;
    83          }
    84          return wrappedBuffer(((MessageLite) msg).toByteArray());
    85      }
    86  }