Mule Dev Tricks: DataWeave Using Reduction

Introduction

In this post, I am going to demonstrate how to convert an array of JSON payload to a single JSON payload.

Input

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[   {     "worker_id": "AMAGWK00002673",     "position_id": "35119973",     "requisition_id": "R-32353",     "applicant_id": "199505",     "staff_id": "199504"   },   {     "worker_id": "AMAGWK00002674",     "position_id": "35119943",     "requisition_id": "R-32353",     "applicant_id": "199505",     "staff_id": "199506"   },   {     "worker_id": "AMAGWK00002675",     "position_id": "35119975",     "requisition_id": "R-32354",     "applicant_id": "199507",     "staff_id": "199508"   } ]

Desired Output

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{   "AMAGWK00002673": "199504",   "AMAGWK00002674": "199506",   "AMAGWK00002675": "199508" }

Solution

The first step is to use dataweave to extrace the worker_id. This is very straight forward. The only trick about this piece of script is to use value as key in the transformed JSON result. This is achieved by using ($.key) : $.otherKey. here key = worker_id and the otherKey is staff_id.

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payload map ((value, index) -> {      (value.worker_id): value.staff_id })

The above dataweave script will produce the following result:

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[   {     "AMAGWK00002673": "199504"   },   {     "AMAGWK00002674": "199506"   },   {     "AMAGWK00002675": "199508"   } ]

In order to produce the final result, we need to use reduction reduce($$ + $).

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payload map ((value, index) -> {      (value.worker_id): value.staff_id }) reduce($$ ++ $)

Note: You have to use reduce ($$ ++$). The round bracket is important! The MuleSoft documentation missed that which causes many confusions.