To allow you to propagate information about the content type of produced messages, Spring Cloud Stream attaches, by default, a contentType header to outbound messages. For middleware that does not directly support headers, Spring Cloud Stream provides its own mechanism of automatically wrapping outbound messages in an envelope of its own. 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: