Spring Cloud Stream allows to propagate information about the content type of the messages it produces by attaching by default a contentType header to outbound messages.
For middleware that does not directly support headers, Spring Cloud Stream provides its own mechanism of wrapping outbound messages in an envelope of its own, automatically.
For middleware that does support headers, Spring Cloud Stream applications may receive messages with a given content type from non-Spring Cloud Stream applications.
Spring Cloud Stream can handle messages based on this information in two ways:
contentType settings on inbound and outbound channels;@StreamListener-annotated methods.