question Re: NiFi: How to extract the size of a JSON array into an attribute? in Support Questions

NiFi: How to extract the size of a JSON array into an attribute?

patrick_hochste — Wed, 29 May 2019 21:14:00 GMT

In my flow file I have JSON content which contains an array. How can I extract the size of that array into an attribute (e.g. my.array.size = 5)?

Re: NiFi: How to extract the size of a JSON array into an attribute?

Shu_ashu — Thu, 30 May 2019 08:59:51 GMT

@Patrick Hochstenbach

You can use SplitJson processor to split the array($.*) into individual flowfile then split json processor adds fragment.count attribute to the flowfile which is array size.

Use UpdateAttribute processor to change the attribute name.

Use MergeContent processor to merge back the content using Defragment strategy.

Re: NiFi: How to extract the size of a JSON array into an attribute?

patrick_hochste — Mon, 03 Jun 2019 14:07:27 GMT

Thanks, I was hoping for an easy trick because I needed many of these calculations. Maybe I need to write a custom processor for this.

Re: NiFi: How to extract the size of a JSON array into an attribute?

Shu_ashu — Tue, 04 Jun 2019 09:58:02 GMT

@Patrick Hochstenbach

Yes,You can consider custom processor/custom script for this, to do this in easier way and add the attribute to the flowfile with array size.

Re: NiFi: How to extract the size of a JSON array into an attribute?

antonisr11 — Thu, 13 Oct 2022 19:28:42 GMT

You can use EvaluateJsonPath. You only have to add an extra attribute and name it as you want (e.g. count) and set as value "$.my.array.size.length()". Then select Destination and change it to flowfile-attribute. This processor will produce a flowfile which has your extra attribute