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.

log(String, T): T

Without changing the value of the input, log returns the input as a system log.

Use this function to help with debugging DataWeave scripts. A Mule app outputs the results through the DefaultLoggingService, which you can see in the Studio console.


Name Description


An optional string that typically describes the log.


The value to log.


This example logs the specified message. Note that the DefaultLoggingService in a Mule app that is running in Studio returns the message WARNING - "Houston, we have a problem," adding the dash `- between the prefix and value. The Logger component’s LoggerMessageProcessor returns the input string "Houston, we have a problem.", without the WARNING prefix.


%dw 2.0
output application/json
log("WARNING", "Houston, we have a problem.")


WARNING - "Houston, we have a problem."

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