FIXMessageEncoder#encode() may throws protocol handler exception: java.nio.BufferOverflowException, if message contains Chinese characters.

we use "UTF-8" as default charset instead of "ISO-8859-1". So charsetEncoding = "UTF-8".

FIXMessageEncoder#encode() :
   ByteBuffer buffer = ByteBuffer.allocate(fixMessageString.length());
   try {
      buffer.put(fixMessageString.getBytes(charsetEncoding));
   } catch (UnsupportedEncodingException e) {
      throw new ProtocolCodecException(e);
   }

if message contains Chinese characters, fixMessageString.length() will not equal to fixMessageString.getBytes(charsetEncoding).length. Because A Chinese character will use "three" Bytes in "UTF-8". But in String, it's length is still "1".

we let: byte[] src = fixMessageString.getBytes(charsetEncoding);
when a message contains "one" Chinese character,
if fixMessageString.length() = 190, then src.length = 192, buffer.capacity() = 256. So buffer.put(src) will not throw java.nio.BufferOverflowException;
if fixMessageString.length() = 255, then src.length = 257, buffer.capacity() = 256. At this time, buffer.put(src) will throw java.nio.BufferOverflowException;

solution:
   use "fixMessageString.getBytes(charsetEncoding).length" to allocate buffer space instead of "fixMessageString.length()".

    ByteBuffer buffer;
    try {
        byte[] src = fixMessageString.getBytes(charsetEncoding);
        buffer = ByteBuffer.allocate(src.length);
        buffer.put(src);
    } catch (UnsupportedEncodingException e) {
        throw new ProtocolCodecException(e);
    }