JsonPath.Net - use query to flatten data structure

Question

Using JsonPath.Net, is it possible to write a single query that will obtain the values of properties with the same key at different nesting levels?

For example, from the following JSON:

{
  "ObjA" : {
    "textValue" : "a1",
    "numValue" : 1
  },
  "ObjB" : {
    "objArray": [
      {
        "textValue": "b1",
        "numValue" : 1
      },
      {
        "textValue": "b2",
        "numValue" : 2
      }
    ]
  }
}

Can we get a list of all "textValue", i.e:

[
  "a1",
  "b1",
  "b2"
]

Or all "numValue", i.e:

[
  1,
  1,
  2
]

I have been trying to do this on https://json-everything.net/json-path/, but I can't figure out how.

Leland · Accepted Answer · 2024-10-29 03:22:50Z

2

JsonPath.Net supports the recursive descent operator ... You can use it to descend the JSON hierarchy, then pick out a particular property by adding the property name after the .. like so:

var rootJsonNode = JsonNode.Parse(jsonText);

var path = JsonPath.Parse("$..textValue");
var results = path.Evaluate(rootJsonNode);                        
var newArray = JsonSerializer.SerializeToNode(results.Matches.Select(m => m.Value))!.AsArray();

Or

var path = JsonPath.Parse("$..numValue");

Demo fiddle here.

For confirmation, see RFC 9535: JSONPath: Query Expressions for JSON :

Syntax Element Description

..[<selectors>] descendant segment (Section 2.5.2): selects zero or more descendants of a node

..name shorthand for ..['name']

..* shorthand for ..[*]

edited Oct 29, 2024 at 3:22

Leland

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answered Oct 29, 2024 at 3:11

dbc

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1 Comment

Cliff Pennalligen Over a year ago

This is a thorough explanation. I must read through the entire RFC.

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Syntax Element	Description
`..[<selectors>]`	descendant segment (Section 2.5.2): selects zero or more descendants of a node
`..name`	shorthand for `..['name']`
`..*`	shorthand for `..[*]`

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