Count length of JSON array in non-blocking way ?

You can do this in an XMLXQueryExtractor which I think is non blocking

e.g. if your json looks like this

{
    "id" : 1,
    "data" : [
            {"x" : 1},
            {"x" : 2},
            {"x" : 3},
            {"x" : 4}
        ]
}

You can do something like this to get the size of the array

jn:size(fme:get-json-attribute("json")("data"))

Thanks ​@ebygomm 

It looks promising.

My array JSON query is: json[*][*][“nodes”]

How would that be expressed in XQuery ?

You could use a JSONFlattener on your JSON response. The JSON list would convert to an FME List attribute. Then you could use a ListElementCounter !

Are you able to share some example json?

This is a good attempt.

I thought it would be messy, but not really.

However, one of the obstacles I have here is that the hierarchial path to the nodes array in the response has a variable name embedded within it, so exposing the array by name in JSONFlattener (or AttributeExposer) isn’t possible.

It’s basically “data.$(SERVICE_NAME).nodes{}” where SERVICE_NAME is a variable parameter value.

E.g. “data.GEODKV_Kommuneomraade.nodes{}”. I have no say in problematic naming.

So I’m stuck with an unexposed array, which I cannot get ListElementCounter to process :-(

Any thoughts on how to remedy this ?

Cheers.

Of course. Here’s a small sample:

{
	"data": {
		"GEODKV_Kommuneomraade": {
			"pageInfo": {
				"endCursor": "TVRJd01ERTROVFExTURJd01qRXdNekV5TVRneE5ESXpOemM9",
				"hasNextPage": true
			},
			"nodes": [
				{
					"kommunekode": "0787"
				},
				{
					"kommunekode": "0787"
				}
			]
		}
	}
}

But beware, the “GEODKV_Kommuneomraade” part is not static, but a variable service name, depending on which service I query. And I need to build a generic handling that works on all services.

This is a reponse from a GraphQL query.

Would this sort of approach work?

Can you try it in the json extractor/fragmentor with .size? Like this : json[*][*][“nodes”].size

I found this in the json query section of the fragmenter:

JSON Property Expressions

A property expression is a structure expression as described above, followed by a . (dot) operator and a property name. Currently, the only supported properties are type and size. The type property returns the type of the JSON value referred to by the JSON structure expression. For example, if the outermost JSON element is an array, and the first element of the array is a string, then the expression json[0].type would have a value of string. The size property, which can only be applied to an array, returns the number of elements in the array.

So the .size sounds like what you need.

Nice!