DataWeave 2.1 is compatible with Mule 4.1. Standard Support for Mule 4.1 ended on November 2, 2020, and this version of Mule will reach its End of Life on November 2, 2022, when Extended Support ends.

Deployments of new applications to CloudHub that use this version of Mule are no longer allowed. Only in-place updates to applications are permitted.

MuleSoft recommends that you upgrade to the latest version of Mule 4 that is in Standard Support so that your applications run with the latest fixes and security enhancements.

failIf(T, (value: T) -> Boolean, String): T

Produces a failure with the specified message if the expression in the evaluator returns true. If not true, returns the value.


Name Description


The value to return only if the evaluator expression is false.


Expression that returns true or false.


This example produces a failure (instead of a { "result": "SUCCESS" } message) because the expression isEmpty(empty) is true. The empty variable defines an empty object.


%dw 2.0
import failIf from dw::Runtime
var empty = {}
var notEmpty = { "a" : "b" }
output application/json
{ "result" : "SUCCESS" failIf (isEmpty(empty)) }


  at fail (Unknown)
  at dw::Runtime::failIf (line: 97, column: 26)
  at main (line: 7, column: 24)

In the Studio console component, the output looks something like this:

ERROR 2018-07-29 11:56:39,988 ...
Message               : "Failed

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