Array size using jsonpath expression - Stefan Goessner JsonPath

Question

I'm having a problem with finding an array or list size using Stefan Goessner's JsonPath. I'm using the version json-path-2.0.0.

My jsonpath expression is $.orders.length and JSON looks something like this:

{
  "orders" : [
    ...
  ]
}

Its failing with the following error:

com.jayway.jsonpath.PathNotFoundException: Property ['length'] not found in path $['orders']

And I tried with $.orders.length() too which is again failing with the below error:

com.jayway.jsonpath.PathNotFoundException: Property ['length()'] not found in path $['orders']

Please suggest me how to get the length of the array using Goessner's JsonPath expression.

[EDIT] Following is how I'm obtaining the configuration:

    com.jayway.jsonpath.Configuration conf = com.jayway.jsonpath.Configuration.defaultConfiguration().addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL);
    DocumentContext documentContext = JsonPath.using(conf).parse(orderJson);
    Object val = documentContext.read(jsonPathExpression);

Solution

It seems that support for returning the length() of an array was only added in version 2.1.0 of the jayway json-path library.

Based on some quick tests, the $.orders.length() expression seems to work with both version 2.1.0 and version 2.2.0, so I think you just need to upgrade your dependency version in order to fix the error you are seeing.

Comments

[DaFois]

Please always add an explanation to the code. it will improve the quality of the answer

[Alex Rewa]

A small correction, seems that it should be $.orders.length (without ()), just tested and works fine for me

[Võ Quang Hòa]

@AlexRewa I tried and it doesn't work on my side with the error message java.lang.AssertionError: No value at JSON path "$.length". But "$.length()" works fine

[Alex Rewa]

@VõQuangHòa, weird... seems it depends on JsonPath implementation.