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.

write(Any, String, Object): String | Binary

Writes (as a String or Binary) the given value in a specific format.

Returns a string or binary with the serialized representation of the value in the specified mimeType (format). You might use this function when you need some data in a format different from the script output, for example to embed data as JSON/CSV inside an XML.


Name Description


The value to write. The value can be of any supported data type.


A supported format (or content type) to write. Default: application/dw.


Optional: Sets writer configuration properties for the particular content type. For writer configuration properties (and other content types), see DataWeave Output Formats and Writer Properties.


This example takes JSON input and writes the payload to a CSV format that uses a pipe (|) separator and includes the header (matching keys in the JSON objects). Note that if you instead use "header":false in your script, the output will lack the Name|Email|Id|Title header in the output.


    "Name": "Mr White",
    "Email": "white@mulesoft.com",
    "Id": "1234",
    "Title": "Chief Java Prophet"
    "Name": "Mr Orange",
    "Email": "orange@mulesoft.com",
    "Id": "4567",
    "Title": "Integration Ninja"


%dw 2.0
output application/xml
  "output" : write(payload, "application/csv", {"header":true, "separator" : "|"})


<?xml version="1.0" encoding="US-ASCII"?>
Mr White|white@mulesoft.com|1234|Chief Java Prophet
Mr Orange|orange@mulesoft.com|4567|Integration Ninja

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