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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.

log(String, T): T

Logs the specified value with an optional prefix, then returns the value unchanged. The function logs the output as a system log.

This function can be used to debug DataWeave scripts until a proper debugger is incorporated.


Name Description


A string that typically describes the log.


The value to log.


This example produces the output shown below in a Logger (through the Mule LoggerMessageProcessor), while the Mule DefaultLoggingService prints My Age - 33 in the console output.


%dw 2.0
output application/xml
var myvar = { "age" : 33 }
{ "age": log("My Age", myvar.age) }


<?xml version="1.0" encoding="UTF-8"?>
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