Do you mean to leave attribute as `object-mapper`? Agree.
From other side I've changed a bit my mind and thought that **serializer** means some narrow sphere of application, so I wanted to rename `JsonSerializer` to the `JsonMapper` (or `ObjectMapper` as you mentioned) to be more compatible with Jackson's one: it's not full serializer as similar abstraction in the Spring, it's not converter, because we use the last one to convert from/to Message.
And one more thought: how about to allows provide  Jackson's `ObjectMapper` ref as it is now? At least before SI 3.1 and say that it is deprecated. In this case guys with Jackson 1.x don't have to change their configs at all.
I think I'll be able to do something in the parser to divide a level of responsibility.
WDYT?