What are the main differences between UpdateAttribute and EvaluateJsonPath operators in NiFi?

Question

Recently started working with NiFi and started wondering what are really the differences between those two operators - UpdateAttribute and EvaluateJsonPath? The flows in my project are using both of them to create attributes in Flowfile, and for now I can't really understand what's the difference, as they both seem to be doing more or less the same thing?..

I was reading the docs for them, and saw that:

UpdateAttribute: This processor updates the attributes of a FlowFile using properties or rules that are added by the user. There are three ways to use this processor to add or modify attributes.

• One way is the "Basic Usage"; this allows you to set default attribute changes that affect every FlowFile going through the processor.
• The second way is the "Advanced Usage"; this allows you to make conditional attribute changes that only affect a FlowFile if it meets certain conditions. It is possible to use both methods in the same processor at the same time.
• The third way is the "Delete Attributes Expression"; this allows you to provide a regular expression and any attributes with a matching name will be deleted.

EvaluateJsonPath: Evaluates one or more JsonPath expressions against the content of a FlowFile. The results of those expressions are assigned to FlowFile Attributes or are written to the content of the FlowFile itself, depending on configuration of the Processor.

It seems that UpdateAttribute can also take the data from JSON and it is at least more flexible as it can also delete attributes?

Answer 1

They are two completely different processors. UpdateAttribute is used to manipulate or create an attribute within the FlowFile, while EvaluateJsonPath is used to extract values from a JSON and insert them either within the FlowFile itself or in its attributes.