JsonPath array length() returns number of keys instead of elements

Question

I have the following array:

"books" : [ {
  "title" : "History",
  "id":1

}, {
  "title" : "The Robotics",
  "id":2

}, {
  "title" : "The World",
   "id":3
} ]

and my JsonPath notation is this: $.books[?(@.title == 'History')].length() . I'm expecting it to return 1 (because it matches a single book), but it returns 2, which is a number of keys in the first object(that got matched). How can I force/change it to return the number of elements, not keys in the object?

Im using this library for java.

TimonNetherlands · Accepted Answer · 2021-03-02 11:44:29Z

1

The problem lies in the dot (.). You have only one but you need two. This works:

$..books[?(@.title == 'History')].length()

edited Mar 2, 2021 at 11:44

answered Mar 2, 2021 at 10:30

TimonNetherlands

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5 Comments

sparrow2 Over a year ago

Thanks @Timon. The thing is that I don't write the java code, Im using library that does this for me. The strange thing is that when I write $.books.length() it returns 3 as expected , but if I have filter and then length() , it counts keys in object

TimonNetherlands Over a year ago

I've updated the answer with a working solution.

sparrow2 Over a year ago

It still gives me 2, but I guess this is due to the library Im using. Thanks anyway

sparrow2 Over a year ago

Btw, how can I check if array is empty, I tries empty(), but does not work

TimonNetherlands Over a year ago

It seems my answer doesn't help. This code always returns length 1. I'll remove this answer in a few minutes.

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