How to convert data from object to string in mule 4? - mule

Question

I used to convert payload to string whenever i need to log the payload on console using the syntax in mule 3 [message.payloadAs(java.lang.String)] and some times used to use object to string converter or object to array converter.
But in mule 4 i don't see any converter as in mule 3 and [message.payloadAs(java.lang.String)] is alos not working.
Please assist me any new syntax of component or consept has come in mule 4 ?
Input
[
{
"firstName": "Ram",
"lastName": "Ram1",
"address": [
{
"street": "a",
"city": "b",
"state": "c"
},
{
"street": "a1",
"city": "b1",
"state": "c1"
}
]
}
Batch Image
Code
<batch:job jobName="Batch_ProcessingBatch_Job" doc:id="2582eccb-720f-499f-99fe-424cab3c9a33" >
<batch:process-records >
<batch:step name="Batch_Step1" doc:id="cb045f6b-edd3-426f-8f28-0d20b301fb6d" >
<logger level="INFO" doc:name="Logger" doc:id="2491184f-e8d7-47b7-bef0-29bafd43247f" message="In Batch_step1........... #[payload]"/>
<batch:aggregator doc:name="Batch Aggregator" doc:id="aa9c1b60-395f-4376-804d-bced200dfb43" size="2">
<set-payload value='#[write(payload, "application/json")]' doc:name="Set Payload" doc:id="9d4b27ee-5692-4a99-a93e-bd7c694f398d" />
<ee:transform doc:name="Transform Message" doc:id="06064422-1352-4ff9-8817-3e87eb1f4264" >
<ee:message >
<ee:set-payload ><![CDATA[%dw 2.0
output application/json
---
payload map(item,index) -> {
name: item.firstName,
surname: item.lastName
}]]></ee:set-payload>
</ee:message>
</ee:transform>
<logger level="INFO" doc:name="Logger" doc:id="c955490e-fab1-436e-8265-f706a577c9d2" message="In Batch_step1 Aggrigator........... #[payload]" />
</batch:aggregator>
</batch:step>
</batch:process-records>
<batch:on-complete >
<logger level="INFO" doc:name="Logger" doc:id="a3923c90-557b-4955-9c40-afd748719abd" message="#['#####It is oncomplete result####': write(payload, "application/json")]"/>
</batch:on-complete>
</batch:job>
Getting Error
Message : "You called the function 'map' with these arguments:
1: String ("[\n \"{\\n \\\"firstName\\\": \\\"Ram\\\",\\n \\\"lastName\\\": \\\"Ram1\...)
2: Function ((item:Any, index:Any) -> ???)
But it expects arguments of these types:
1: Array
2: Function
4| payload map(item,index) -> {
| ...
7| }
Trace:
at map (line: 4, column: 1)
at main (line: 4, column: 9)" evaluating expression: "%dw 2.0
output application/json
---
payload map(item,index) -> {
name: item.firstName,
surname: item.lastName
}".
Error type : MULE:EXPRESSION
Element : Batch_ProcessingFlow/processors/0/route/0/route/0/aggregator/processors/1 # training-1:Batch Processing.xml:27 (Transform Message)
Element XML : <ee:transform doc:name="Transform Message" doc:id="06064422-1352-4ff9-8817-3e87eb1f4264">
<ee:message>
<ee:set-payload>%dw 2.0
output application/json
---
payload map(item,index) -> {
name: item.firstName,
surname: item.lastName
}</ee:set-payload>
</ee:message>
</ee:transform>
(set debug level logging or '-Dmule.verbose.exceptions=true' for everything)
********************************************************************************

Answer 1

After quick googling the new way is to use #[message.payload as String] as shown in link.

Answer 2

You can use the payload.^raw syntax for the loggers. It was introduced in mule 4 and can handles cases where string conversion is needed. Typically pairs well with output text/plain format in a logger.
Ref: https://docs.mulesoft.com/mule-runtime/4.3/dataweave-cookbook-extract-data#metadata_selector
NOTE its never a good idea to log entire payloads (that could contain PII etc..) with maybe an exception where you are building a report that you need to log at the end of your batch process which possibly could be the case here...