How to throw an error message if id field exist in POST request in Mulesoft 4

How to check if id in post request should not be included. I have 2 scenarios.

request body:

 {
    "name"="John"
 }

Expected result:

"Success"

request body:

 {
    "id"="323",
    "name"="Jane"
 }

Expected result: "id field should not be specified."

Solution

The following code will help you with what you are looking for

%dw 1.0
%output application/json
---
{
    output: 'ID field should not be specified' 
    when payload.id? otherwise 'Success'
}

in mule 4: when otherwise has been replaced with if else. here is the dataweave code

%dw 2.0
output application/json
---

if (payload.id?)
  { result: "ID field should not be specified" }
else { result: "Success" }