Fixes#505
The goals are twofold: to simplify the registration of new converters and
to add some consistency to the conversion process, and align them with the
way converters are used in generic Spring Messaging listeners, by describing
two possible transformations: inbound, message (including contentType)->targetClass,
and outbound payload+headers -> message. The idea is for the two
transformations to match the input and output directions of the bound channels.
List of changes:
- Create and configure input/output channels distinctly - reflected
in the definitions of `BindableChannelFactory` and `MessageChannelConfigurer`;
- Replace AbstractFromMessageConverter with bidirectional converters;
- Use the channel direction (input/output) to determine whether
`toMessage` or `fromMessage` will be invoked;
- Use contentType support from `AbstractMessageConverter` to map
converters to mime types instead;
Making converters more robust
Addressing comments
Convert content type headers to String before serializing
Addressing further PR comments
Handle common aspects of message-channel binders:
- added generic, customizable ReceivingHandler and SendingHandler
- made doBindProducer delegate to a series of template methods
- made doBindConsumer delegate to a series of template methods
- moved partitioning to an interceptor, thus fixing #493
Removed unused manual ack handling
