Extract Key-Value Pairs with `Pluck` Function

In addition to using the DataWeave functions such as entriesOf, keysOf, or valuesOf to work with key-value pairs, you can also use pluck. The following Mule app example shows how to use the DataWeave pluck function to extract key-value pairs from a JSON payload and store them into Mule event variables with variable names as the keys and their corresponding values.

The Mule app consists of:

A Scheduler component that triggers the flow
A Set Payload component that sets the JSON payload
A Transform Message component that transforms the content read from the Set Payload component by extracting the key-value pairs with the pluck function and putting them into an array
A For Each scope component that iterates over the array
A Set Variable component that sets the variable name as the Key and variable value as the Value in the JSON array
A Logger component that prints the variable results per each iteration

Application XML File (reformatted for readability):

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

<mule xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core"
      xmlns="http://www.mulesoft.org/schema/mule/core"
      xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/ee/core http://www.mulesoft.org/schema/mule/ee/core/current/mule-ee.xsd">
      <flow name="json-varsFlow" >
            <scheduler doc:name="Scheduler" >
	          <scheduling-strategy >
		        <fixed-frequency frequency="10000"/>
                  </scheduling-strategy>
	    </scheduler>
	    <set-payload value='{"firstName": "jason", "job": "engineer", "dept":"support"}'
	                 doc:name="Set Payload"
			 mimeType="application/json" />
	    <ee:transform doc:name="Transform Message" >
	          <ee:message >
		        <ee:set-payload ><![CDATA[%dw 2.0
output application/json
---

payload pluck (value,key)  -> {
	Test:{
		Key: key,
		Value: value
	}
}]]></ee:set-payload>
                  </ee:message>
            </ee:transform>
	    <foreach doc:name="For Each"
	             collection="#[payload.Test]">
	                <logger level="INFO" doc:name="Logger" message="#[payload]" />
		        <set-variable value="#[payload.Value]"
		                      doc:name="Set Variable"
				      variableName="#[payload.Key]"/>
		        <logger level="INFO"
		                doc:name="Logger"
			        message="#[vars[payload.Key]]"/>
            </foreach>
      </flow>
</mule>

Note that the Transform Message configures the following DataWeave script:

%dw 2.0
output application/json
---
payload pluck (value,key)  -> {
  Test: {
    Key: key,
    Value: value
  }
}

When the the Mule app executes with the following JSON payload:

{
  "firstName": "jason", "job": "engineer", "dept":"support"
}

The DataWeave transformation result is:

[
  {
    "Test": {
      "Key": "firstName",
      "Value": "jason"
    }
  },
  {
    "Test": {
      "Key": "job",
      "Value": "engineer"
    }
  },
  {
    "Test": {
      "Key": "dept",
      "Value": "support"
    }
  }
]

The For Each scope component iterates over the transformed values, and the app logs the values of the variable results (reformatted for readability):

INFO  2022-06-22 10:11:17,864 [[MuleRuntime].uber.02:
      [jsonsample].json-varsFlow.CPU_INTENSIVE @5c652aa]
      [processor: json-varsFlow/processors/2/processors/0; event: 545f5ef0-f24e-11ec-8c92-147ddaaf4f97]
      org.mule.runtime.core.internal.processor.LoggerMessageProcessor:
      {
          "Key": "firstName",
	  "Value": "jason"
      }
INFO  2022-06-22 10:11:17,870 [[MuleRuntime].uber.02: [jsonsample].json-varsFlow.CPU_INTENSIVE @5c652aa]
      [processor: json-varsFlow/processors/2/processors/2; event: 545f5ef0-f24e-11ec-8c92-147ddaaf4f97]
      org.mule.runtime.core.internal.processor.LoggerMessageProcessor:
      "jason"
INFO  2022-06-22 10:11:17,871 [[MuleRuntime].uber.02: [jsonsample].json-varsFlow.CPU_INTENSIVE @5c652aa]
      [processor: json-varsFlow/processors/2/processors/0; event: 545f5ef0-f24e-11ec-8c92-147ddaaf4f97]
      org.mule.runtime.core.internal.processor.LoggerMessageProcessor:
      {
        "Key": "job",
        "Value": "engineer"
      }
INFO  2022-06-22 10:11:17,875 [[MuleRuntime].uber.02:
      [jsonsample].json-varsFlow.CPU_INTENSIVE @5c652aa]
      [processor: json-varsFlow/processors/2/processors/2; event: 545f5ef0-f24e-11ec-8c92-147ddaaf4f97]
      org.mule.runtime.core.internal.processor.LoggerMessageProcessor:
      "engineer"
INFO  2022-06-22 10:11:17,877 [[MuleRuntime].uber.02:
      [jsonsample].json-varsFlow.CPU_INTENSIVE @5c652aa]
      [processor: json-varsFlow/processors/2/processors/0; event: 545f5ef0-f24e-11ec-8c92-147ddaaf4f97]
      org.mule.runtime.core.internal.processor.LoggerMessageProcessor:
      {
         "Key": "dept",
	 "Value": "support"
      }
INFO  2022-06-22 10:11:17,879 [[MuleRuntime].uber.02: [jsonsample].json-varsFlow.CPU_INTENSIVE @5c652aa]
      [processor: json-varsFlow/processors/2/processors/2; event: 545f5ef0-f24e-11ec-8c92-147ddaaf4f97]
      org.mule.runtime.core.internal.processor.LoggerMessageProcessor:
      "support"

Extract Key-Value Pairs with Pluck Function

See Also

Extract Key-Value Pairs with `Pluck` Function