Nifi: How can i replace text only in some specific fields using ReplaceText processor

[#1]

Greetings,

I have a NIFI flow in which I change a log to a JSON format file and then I need to remove space characters in some of the fields inside the JSON.
I use the ReplaceText processor and I need to know how to limit it so that it performs the replacement operation only on specific fields that I define for it.

Thank you!!

[#2]

Dont know if it is the best solution, but if you know the keys of the JSON, you can use the Processor 'EvaluateJsonPath' and put the values as attribute to the flowfile.

Then use Processor 'AttributsToJson' and set the JSON key and the value with expression language ${attr:trim()}