Mule Dev Tricks: DataWeave - Using mapObject - Part IV

Introduction

In my last post I covered the topic of removing null object and empty strings from JSON payload. That solution is only good for two level of objects. If the JSON hierarchy has multiple level, then it would not work. In that case, we need to use recursion. This post will show the solution for this purpose.

Sample Input

[
  {
    "first_name" : "Gary",
    "middle_name" : "",
    "last_name" : "Liu",
    "address" : {
     "street" : {
      "number" : "",
      "name" : ""
     },
     "city" : null,
     "zip" : null
    }
  }
]

Desired Output

[
  {
    "first_name": "Gary",
    "last_name": "Liu"
  }
]

Solution

%dw 1.0
%output application/json

%function skipNulls(o) o 
    unless o is :object 
    otherwise o mapObject {
        (($$): skipNulls($)) when ($ != null and $ != "")
    }

%function skipEmpty(o) o
 unless o is :object 
    otherwise o mapObject {
        (($$): skipEmpty($)) when ($ != {} and $ != '')
    }

---
payload map ((person)  -> { 
 (skipEmpty(person mapObject { 
         ($$): skipNulls($)
     })
 )
 
})

Key Learning Points

In the solution given here, I used the recursion as the following:

%function skipNulls(o) o 
    unless o is :object 
    otherwise o mapObject {
        (($$): skipNulls($)) when ($ != null and $ != "")
    }

This demonstrates that dataweave functions allow us to use the recursion concept. The code provide here is not perfect yet. There is a bug I am working on.