JsonPath - Filter Array and get only the first element

Question

Im trying to filter the elements of this JSON array to return only the first element it will find.

{
    "elements": [{
        "urn": "urn:li:lyndaCourse:189800",
        "details": {
            "classifications": [{
                    "associatedClassification": {
                        "urn": "urn:li:lyndaCategory:9331",
                        "type": "LIBRARY"
                    }
                },
                {
                    "associatedClassification": {
                        "urn": "urn:li:lyndaCategory:8982",
                        "type": "SUBJECT"
                    }
                },
                {
                    "associatedClassification": {
                        "urn": "urn:li:lyndaCategory:8920",
                        "type": "LIBRARY"
                    }
                }
            ]
        }
    }]
}

But this results in an EMPTY array [].

I tried this JSONPATH query in https://jsonpath.herokuapp.com/

$.elements[0].details.classifications..associatedClassification[?(@.type=='LIBRARY')][0]

Expecting to get:

[{
    "urn": "urn:li:lyndaCategory:9331",
    "type": "LIBRARY"
}]

Delta George · Accepted Answer · 2022-04-10 09:35:49Z

4

The following works on all elements:

$..classifications[?(@.associatedClassification.type=='LIBRARY')]

and returns a list of all matching associatedClassification objects.

JSONPath is expected to point inside the original document. Therefore, getting the first element from the result list would require post-processing, e.g. a separate JSONPath, e.g.

$.[0]

answered Apr 10, 2022 at 9:35

Delta George

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2 Comments

David Marciel Over a year ago

Thank you! It took me a lot to find this solution.

juanpa.arrivillaga Feb 6 at 21:44

naively, I find this ridiculous, but thank you for confirming.

Brank Victoria · Accepted Answer · 2022-03-31 14:10:52Z

3

Another way to filter the information is by filtering the property "classification" (without using ".."), and use "associatedClassification.type" in your filter, so you should have something like this:

$.elements[0].details.classifications[?(@.associatedClassification.type=='LIBRARY')]

With the above JSONPATH you will have all items which type is "LIBRARY" (in your example will return 2 items).

You mentioned you need only the first one of the filtered items, as far as I investigated it seems there's no posible solution to return only the first item using only JSONPATH (see the thread bellow):

https://github.com/json-path/JsonPath/issues/272

edited Mar 31, 2022 at 14:10

answered Mar 30, 2022 at 13:01

Brank Victoria

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2 Comments

Infor.KS Over a year ago

In my testing, the .. works, and its also documented here github.com/json-path/… anyway - my main problem is getting the first item of the result set and yeah it looks like it can't be done just by jsonpath.

Brank Victoria Over a year ago

You're totally right, I didn't know it, I will modify the answer, thank you

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