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    1   /*
    2    *  Licensed to the Apache Software Foundation (ASF) under one
    3    *  or more contributor license agreements.  See the NOTICE file
    4    *  distributed with this work for additional information
    5    *  regarding copyright ownership.  The ASF licenses this file
    6    *  to you under the Apache License, Version 2.0 (the
    7    *  "License"); you may not use this file except in compliance
    8    *  with the License.  You may obtain a copy of the License at
    9    *
    10   *    http://www.apache.org/licenses/LICENSE-2.0
    11   *
    12   *  Unless required by applicable law or agreed to in writing,
    13   *  software distributed under the License is distributed on an
    14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    15   *  KIND, either express or implied.  See the License for the
    16   *  specific language governing permissions and limitations
    17   *  under the License.
    18   *
    19   */
    20  package org.apache.mina.example.sumup.codec;
    21
    22  import org.apache.mina.core.buffer.IoBuffer;
    23  import org.apache.mina.core.session.IoSession;
    24  import org.apache.mina.example.sumup.message.AbstractMessage;
    25  import org.apache.mina.filter.codec.ProtocolEncoderOutput;
    26  import org.apache.mina.filter.codec.demux.MessageEncoder;
    27
    28  /**
    29   * A {@link MessageEncoder} that encodes message header and forwards
    30   * the encoding of body to a subclass.
    31   *
    32   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
    33   */
    34  public abstract class AbstractMessageEncoder<T extends AbstractMessage> implements MessageEncoder<T> {
    35      private final int type;
    36
    37      protected AbstractMessageEncoder(int type) {
    38          this.type = type;
    39      }
    40
    41      public void encode(IoSession session, T message, ProtocolEncoderOutput out) throws Exception {
    42          IoBuffer buf = IoBuffer.allocate(16);
    43          buf.setAutoExpand(true); // Enable auto-expand for easier encoding
    44
    45          // Encode a header
    46          buf.putShort((short) type);
    47          buf.putInt(message.getSequence());
    48
    49          // Encode a body
    50          encodeBody(session, message, buf);
    51          buf.flip();
    52          out.write(buf);
    53      }
    54
    55      protected abstract void encodeBody(IoSession session, T message, IoBuffer out);
    56  }