How to Rename JSON Keys in Your Data with DataWeave

This article will explain how one can rename JSON Keys or Fields from the payload containing JSON data, without affecting the other fields present in the payload.

This example includes the below-mentioned functions:

• mapObject to go through the key:value pairs in a JSON object.
• if by itself to determine when to change the name of a key.
• if with and to retain the name of all keys except the two with new names.
• as to coerce the type of the keys into a String.

Input JSON Payload

{
  "Employee":[
  {
  "employeeId":1,
  "firstName":"Alex",
  "lastName":"Davis",
  "email":"alex@abc.com",
  "dob":"12/14/1998"
  },
  {
  "employeeId":2,
  "firstName":"John",
  "lastName":"Dann",
  "email":"john@abc.com",
  "dob":"12/14/1995"
  }]
}

Dataweave Logic

%dw 2.0
output application/json
---
payload.Employee map (emp) -> {
    (emp mapObject (value, key) -> {
        (id: value) if(key as String == 'employeeId'),
        ((key):value) if(key as String !='employeeId')
    })
}

Output JSON

[
  {
    "id": 1,
    "firstName": "Alex",
    "lastName": "Davis",
    "email": "alex@abc.com",
    "dob": "12/14/1998"
  },
  {
    "id": 2,
    "firstName": "John",
    "lastName": "Dann",
    "email": "john@abc.com",
    "dob": "12/14/1995"
  }
]

There is another approach to the same problem using the pattern matching mechanism, The example includes the below-mentioned functions and statements:

• mapObject to go through the key:value pairs in a JSON object.
• match on each key in the input.
• case statements to change the name of matching keys in the input.
• else statement to retain the name of keys that do not require a name change.

%dw 2.0
output application/json

fun renameKey(key: Key) = key match {
    case "employeeId" -> "id"
    else -> (key)
}
---
payload.Employee map (emp) ->
emp mapObject (value, key) -> {
    (renameKey(key)) : value
}