Content type conversion matrix

Introduction

This page documents the expectation one must have when producing and consuming messages via Spring Cloud Stream channel-based binders (i.e., Kafka, Rabbit)

Assumptions and expectations

• The payloads of messages "on-the-wire" is represented as byte[] while "in-binder/in-jvm" it could be anything.
  • toMessage(..) - <T> -> byte[]
  • fromMessage(..) - byte[] -> <T>
• Binders perform serialization (producer) and deserialization (consumer) of payload to/from byte[] utilizing MessageConverters.
• Default content-type is application/json
• Content-type can be set per binding or as Message header
  • --spring.cloud.stream.default.contentType= - default binding
  • --spring.cloud.stream.bindings.<bindingName>.contentType= - per-binding name
• Content-type set as Message header takes precedence over content-type set per binding
• Content-type headers are NOT propagated to preserve flexibility of (re)setting in/out content-type at the handler level (via MessageHeaders) or binding level.

Supported Content-Types

Below is the list of content types supported by the provided MessageConverters

• application/json application/octet-stream
• application/x-java-object (must contain type attribute with FQN of the actual type: application/x-java-object; type=foo.bar.MyClass) - DEPRECATED
• application/x-java-serialized-object - DEPRECATED
• application/x-spring-tuple - DEPRECATED

Inbound content-type	Supported Handler payload type	Outbound content-type	MessageConverter
-	byte[], String, POJO (json friendly)	application/json	ApplicationJsonMessageConverter
application/json	byte[], String, POJO (json friendly)	application/json	ApplicationJsonMessageConverter
text/*	byte[], String	text/* .	ObjectStringMessageConverter
application/x-java-object	byte[], POJO (Kryo)	text/* .
application/x-java-serialized-object	byte[], POJO	application/x-java-serialized-object
application/octet-stream	byte[]	application/octet-stream