Aggregation in ForEach in Mule 4 - mule

Question

I want to aggregate the responses of each iteration of For Each. In each iteration I am getting Json data and I want to aggregate that Json data into Json Array/List. Please let me know how I can do that by using data weave in Transform or by any other way?
Below is sample Json data that I am getting in each iteration of For Each.
1st iteration:
{
"accountId": "12345",
"accountNumber": "999",
"accountTitle": "ABC"
}
2nd iteration:
{
"accountId": "98765",
"accountNumber": "888",
"accountTitle": "XYZ"
}
I want final aggregated output as below.
{
accountList: [
{
"accountId": "12345",
"accountNumber": "999",
"accountTitle": "ABC"
},
{
"accountId": "98765",
"accountNumber": "888",
"accountTitle": "XYZ"
}
]
}

Answer 1

You can follow something like
<!-- Define blank arraylist for aggregation -->
<dw:transform-message doc:name="Transform Message">
<dw:set-variable variableName="result"><![CDATA[%dw 1.0
%output application/java
---
[]]]></dw:set-variable>
</dw:transform-message>
<foreach doc:name="For Each">
<!-- generate response using flow logic and add following step for updating result array -->
<dw:transform-message doc:name="Transform Message">
<dw:set-variable variableName="result"><![CDATA[%dw 1.0
%output application/java
---
flowVars.result ++ [payload]]]></dw:set-variable>
</dw:transform-message>
</foreach>
<!-- Transform aggregated result to any format. I used JSON -->
<dw:transform-message doc:name="Transform Message">
<dw:set-payload><![CDATA[%dw 1.0
%output application/json
---
accountList : flowVars.result]]></dw:set-payload>
</dw:transform-message>
I have used Mule 3.x syntax. For mule 4 you can use attribute instead of variable for storing records. Dataweave syntax will remain same except for changing Dataweave language version from 1.0 to 2.0.
Hope this helps.