Dataweave - how to accumulate json response from http request connector in for each component (Mule 4) - mule

Question

I consume a HTTP request and I need to save and accumulate the JSON response with out any transformation in a variable, I do that but I dont know why the accumulate it correctly, could you please tell me how can I solve that problem.
Json Response By Iteration:
Iteration 1:
{
"orderId": "11111",
"status": "false",
"receivedAt": "2022-07-28T22:45:12.175Z",
"createdAt": "2022-07-28T22:45:12.175Z",
}
Iteration 2:
{
"orderId": "22222",
"status": "false",
"receivedAt": "2022-07-28T22:45:27.907Z",
"createdAt": "2022-07-28T22:45:27.907Z"
}
Dataweave: (csv Payload is the name of the variable where the values accumulated)
%dw 2.0
output application/json
---
if ( vars.counter == 1)
( payload )
else
( vars.csvPayload ) ++ payload
Variable Result:
{
"orderId": "11111",
"status": "false",
"receivedAt": "2022-07-28T22:45:12.175Z",
"createdAt": "2022-07-28T22:45:12.175Z",
"orderId": "22222",
"status": "false",
"receivedAt": "2022-07-28T22:45:27.907Z",
"createdAt": "2022-07-28T22:45:27.907Z"
}
Variable Expected:
[
{
"orderId": "11111",
"status": "false",
"receivedAt": "2022-07-28T22:45:12.175Z",
"createdAt": "2022-07-28T22:45:12.175Z",
},
{"orderId": "22222",
"status": "false",
"receivedAt": "2022-07-28T22:45:27.907Z",
"createdAt": "2022-07-28T22:45:27.907Z"
}
]
NOTE: I don't know why the JSON responses of each iteration are joined in the same object and not as a different object in an array.

Answer 1

The incorrect output is easy. You are concatenating an object to another object. In that case the operator ++ "extracts all the key-values pairs from each object, then combines them together into one result object." according to the documentation. The parenthesis are totally unneeded.
Setting the output to JSON in each iteration -I'm assuming this is inside a foreach- is inefficient since it requires formatting the output to JSON in each iteration only to parse it again in the following one. I recommend to use application/java -which doesn't require parsing/formatting- inside a loop and after the loop convert the entire output to JSON in one go.
You should use an array to hold the values, so assign an empty array ([]) to the variable before the foreach loop to initialize it. Then the counter is unneeded since you can just add elements to the array:
%dw 2.0
output application/java
---
vars.allOrders ++ payload
Then after the foreach just transform the array to JSON:
%dw 2.0
output application/json
---
vars.allOrders

Answer 2

Your requirement is a very common scenario in integrations.
Assuming you are using HTTP Requester inside a for-each loop and initialized the variable to hold the final Payload (lets say var finalPayload = []) before the loop, you have to keep on updating the same variable (append the new data in the same array variable like below) with the response payload received from HTTP Requester for each iteration.
var finalPayload << payload
Ultimately check the finalPayload outside for-each loop, that will give you your desired result.