stream.filter() based on message header

[Jorg Heymans]

Hi, 

I understand that it's currently not possible to access message headers from 
the filter() DSL operation, is there a semantically equivalent (stateless) 
operation that can achieve the same result ? I understand that transform(), 
transformValues() and process() could achieve the same result but they are 
stateful. 

Thanks,
Jorg