In Spring Integration, handlers and interceptors look like they basically achieve the same thing. There are even some 'duped' implementations, such as MessageTransformingChannelInterceptor and MessageTransformingHandler, which as far as I can tell provide the same functionality with different semantics.
Is there a time when one is appropriate and not another? If it's a matter of preference then I'm guessing that there'd be some sort of convention?
Thanks, Roy
My general rule of thumb is to use interceptors sparingly; and typically, only for "passive" things like logging, wire tap etc.
Some users like to do message validation in interceptors; especially if they want to apply the same validation to multiple channels, perhaps with a global interceptor with an appropriate channel pattern.
The transforming interceptor was created in a very early iteration of the framework (2008) and we should probably remove (at least) the only mention of it in the reference (in the XML section).