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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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