The Header Expression Language allows you to extract values of named headers.
The recipientList element of the Spring DSL can utilize a header expression like:
In this case, the list of recipients are contained in the header 'myHeader'.
And the same example in Java DSL:
And with a slightly different syntax where you use the builder to the fullest (i.e. avoid using parameters but using stacked operations, notice that header is not a parameter but a stacked method call)
The Header language is part of camel-core.