@Override
	protected Object convertFromInternal(Message<?> message, Class<?> targetClass, Object conversionHint) {
		MimeType mimeType = contentTypeResolver.resolve(message.getHeaders());
		byte[] converted = null;
		if (mimeType == null || mimeType.getParameter("Charset") == null) {
			converted = ((String) message.getPayload()).getBytes();
		}
		else {
			String encoding = mimeType.getParameter("Charset");
			if (encoding != null) {
				try {
					converted = ((String) message.getPayload()).getBytes(encoding);
				}
				catch (UnsupportedEncodingException e) {
					logger.error(e.getMessage(), e);
				}
			}
		}
		return converted;

	}
Don't need to manipulate message headers. Just return the payload
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/integration/bus/converter/StringToByteArrayMessageConverter.java