public static String decodeExceptionMessage(Message<?> requestMessage) {
		return "Could not convert message: " + DatatypeConverter.printHexBinary((byte[]) requestMessage.getPayload());
	}
Encodes requested headers into payload with format
{@code 0xff, n(1), [ [lenHdr(1), hdr, lenValue(4), value] ... ]}.
The 0xff indicates this new format; n is number of headers (max 255); for
each header, the name length (1 byte) is followed by the name, followed by
the value length (int) followed by the value (json).
<p>
Previously, there was no leading 0xff; the value length was 1 byte and only
String header values were supported (no JSON conversion).

@author Eric Bottard
@author Gary Russell
spring-xd-messagebus-spi/src/main/java/org/springframework/xd/dirt/integration/bus/EmbeddedHeadersMessageConverter.java