Introduction

Since the Vancouver release, there is a new API GlideJsonPath[1] that allows to query a JSON string with jsonPath[2].

The jsonPath can be viewed as the JSON equivalent of the XPath for XML. It allows to perform queries like $.library.bools.*.title for example. Jsonpath is offically a RFC since february 2024[^3]

I suspect the under the hood, it use the implementation JsonPath[5].

Usage of the GlideJsonPath

The official documentation[1] is very succint and there is a couple of extra information that can help:

• the GlideJsonPath expect a String, not an object as parameter
• the read function seems to return an array of JavaObject, which are not the same as the javascript objects. It might need some kind of converstion before being able to use it.

To ease the usage, I suggest to use a function like this one, that accept an Object as parameter and return also a javascript Object:

/*
	@name executeJSONpath
	@description execute the JSON path on the given object and return the result 
	@param {Object} [obj] - Object on which to execute the json path
	@param {String} [jsonPath] - Json path to use for the query
	@return {Object} Object after applying the jsonPath read
*/
function executeJSONpath (obj, path){
  try{
    // Convert the object to a JSON string
    var jsonString = JSON.stringify(obj);

    // call and retrieve the result from GlideJsonPath
    var gjp = new GlideJsonPath(jsonString);
    var gjpResult = gjp.read(path);

    return gjpResult;
    
  } catch (exception){
    gs.error("Error in function 'executeJSONpath' : " + exception + JSON.stringify(exception));
  }
}

##JSON path syntax

The JSON path syntax can be summarized as follow:

dot-notation or bracket-notation

the JsonPath can use either a dot-notation, like $.store.book[0].title or a bracker-notation $['store']['book'][0]['title']

It can also use a mix of both, like this example: $['store']['book'][0].title

Also in the bracket notation, it is possibe to specify mutliple attribute to retrieve, for example: `$[‘store’][‘book’][0].[“title”, “author”]

Elements

The JsonPath can use the following elements [2][3][5]:

• $: The root element to query. This starts all path expressions.
• @: The current node being processed by a filter predicate.
• *: Wildcard. Available anywhere a name or numeric are required.
• ..: Deep scan. Available anywhere a name is required.
• .<name>: Dot-notated child
• ['<name>' (, '<name>')]: Bracket-notated child or children
• [<number> (, <number>)]: Array index or indexes
• [start:end]: Array slice operator
• [?(<expression>)]: Filter expression. Expression must evaluate to a boolean value.

Functions

The specification gives several functions (min(), max(), …), but unfortunately it seems thay are not supported by the ServiceNow implementation.

Operators

For use in the expression, we can use the “classic” operator like “==”, “!=”, “>”, “=>”, etc. It also supports:

• =~: left matches regular expression [?(@.name =~ /foo.*?/i)]
• in: left exists in right [?(@.size in [‘S’, ‘M’])]
• nin: left does not exists in right
• subsetof: left is a subset of right [?(@.sizes subsetof [‘S’, ‘M’, ‘L’])]
• anyof: left has an intersection with right [?(@.sizes anyof [‘M’, ‘L’])]
• noneof: left has no intersection with right [?(@.sizes noneof [‘M’, ‘L’])]
• size: size of left (array or string) should match right
• empty: left (array or string) should be empty

Limitations

• functions: functions are not supported, as stated above
• unique values: There is not way to ask for unique values: there can be duplicated entries (for example when listing all categories)

Example of JSON path

This table show the result of various jsonPath from the GitHub JsonPath documentation[5].

When creating a new jsonPath, you can use this online evaluator[4] to test it

Sample JSON

Here is the sample JSON used for the tests:

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}

References

• [^1]GlideJsonPath | ServiceNow Developers
• [^2]JSON with JSONPath
• [^3]RFC 9535 - JSONPath: Query Expressions for JSON
• [^4]JSONPath Online Evaluator
• [^5]GitHub - json-path/JsonPath: Java JsonPath implementation