Chapter 64. Constant Language

Available as of Camel version 1.5

The Constant Expression Language is really just a way to specify constant strings as a type of expression.

Note

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.

64.1. Constant Options

The Constant language supports 1 options which are listed below.

NameDefaultJava TypeDescription

trim

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks

64.2. Example usage

The setHeader element of the Spring DSL can utilize a constant expression like: 

<route>
  <from uri="seda:a"/>
  <setHeader headerName="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");

64.3. Dependencies

The Constant language is part of camel-core.