Since Camel 1.5
The Constant Expression Language is really just a way to specify constant strings as a type of expression.
This is a fixed constant value that is only set once during starting up the route, do not use this if you want dynamic values during routing.
The Constant language supports 1 options, which are listed below.
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Whether to trim the value to remove leading and trailing whitespaces and line breaks
The setHeader element of the Spring DSL can utilize a constant expression like:
<route> <from uri="seda:a"/> <setHeader name="theHeader"> <constant>the value</constant> </setHeader> <to uri="mock:b"/> </route>
in this case, the Message coming from the seda:a Endpoint will have 'theHeader' header set to the constant value 'the value'.
And the same example using Java DSL:
from("seda:a") .setHeader("theHeader", constant("the value")) .to("mock:b");
You can externalize the constant and have Camel load it from a resource such as
This is done using the following syntax:
"resource:scheme:location", eg to refer to a file on the classpath you can do: