Filter expression return array can not use [index] get item inside

[gyk001]

eg. I want get the price for book "Sayings of the Century"

👍 $.store.book[?(@.title=='Sayings of the Century')] will return an book array
👍 $.store.book[?(@.title=='Sayings of the Century')].price will return an price array

😂 $.store.book[?(@.title=='Sayings of the Century')][0] will return an empty array
😂 $.store.book[?(@.title=='Sayings of the Century')].price[0] will return an empty array

I think $.store.book[?(@.title=='Sayings of the Century')][0] should return a book
$.store.book[?(@.title=='Sayings of the Century')].price[0] should return a price

[kohlsalem]

Somehow i have a similar issue here openhab/openhab1-addons#4768

i there any way to address the item after a filtering has been done?

[kohlsalem]

I found out a possible solution:

$.store.book[?(@.title=='Sayings of the Century')].price.min()

would take the one value from the list...

[kallestenflo]

A path must point to something in the document. That is the case for:

$.store.book[?(@.title=='Sayings of the Century')]

but not with:

$.store.book[?(@.title=='Sayings of the Century')][0]

where the [0] actually is expected to be applied to the result of the path evaluation. I agree that this would useful in many situations but it should not be confused with the actual path.

[apocheau]

My 2 cents.
This is a workaround using read method on the result of the filter:

String filterResult = JsonPath.read(fullJson, "$.store.book[?(@.title == 'Sayings of the Century')]").toJSONString();
Double price = JsonPath.read(filterResult, "$[0].price");

Hope it could help until we will be able to do sort of:
$.store.book[?(@.title=='Sayings of the Century')][0].price

[RamakrishnanArun]

Any chance of getting a way to support this? Would be a nice to have.

[kallestenflo]

@jochenberger whats your thoughts on this?

[jochenberger]

That's a tough one. It's apparently not part of the original JsonPath spec and is not supported on any of the implementations.
I have a similar use case in the project I use JsonPath for and I have decided to create helper methods findAll(object, path) and findFirst(object, path) where the latter calls JsonPath.parse(object).limit(1).read(path) and returns an appropriate response.
I'd say we should stick to the spec and not support this, but it's not a very strong opinion.

[RamakrishnanArun]

I would agree that going off spec is not the best idea yes because then you have an excuse to just add anything even if it deviates spec. Maybe custom functions or some sort of extension capability which is separate from the base project (which is pure spec).

[RamakrishnanArun]

What are the contribution guidelines in terms of "accepting any terms" or processes. I thought I might try experimenting.

[jochenberger]

I don't think there are any terms. Adding tests is a good way to get PRs merged, so is not breaking existing ones. ;-)
#243 seems related btw.

[jochenberger]

And there's also #191 and #197.