Chapter 67. 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.

67.1. Constant Options
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The Constant language supports 1 options, which are listed below.

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Name	Default	Java Type	Description
trim	`true`	`Boolean`	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 headerName="theHeader">
    <constant>the value</constant>
  </setHeader>
  <to uri="mock:b"/>
</route>

<route>
  <from uri="seda:a"/>
  <setHeader headerName="theHeader">
    <constant>the value</constant>
  </setHeader>
  <to uri="mock:b"/>
</route>

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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");

from("seda:a")
  .setHeader("theHeader", constant("the value"))
  .to("mock:b");

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The Constant language is part of camel-core.