DataWeave 2.2 is compatible and bundled with Mule 4.2. Standard Support for Mule 4.2 ended on May 2, 2021, and this version of Mule will reach its End of Life on May 2, 2023, 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.

fail(String): Nothing

Throws an exception with the specified message.


Name Description


An error message (String).


This example returns a failure message Data was empty because the expression (sizeOf(myVar) <= 0) is true. A shortened version of the error message is shown in the Output section below.


%dw 2.0
import * from dw::Runtime
var result = []
output application/json
if(sizeOf(result) <= 0) fail('Data was empty') else result


ERROR 2018-07-29 11:47:44,983 ...
Message               : "Data was empty

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