RFC 9535 - JSONPath: Query Expressions for JSON in Dart

import 'dart:convert';

import 'package:json_path/json_path.dart';

void main() {
  final json = jsonDecode('''
{
  "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
    }
  }
}  
  ''');

  final prices = JsonPath(r'$..price');

  print('All prices in the store:');

  /// The following code will print:
  ///
  /// $['store']['book'][0]['price']:	8.95
  /// $['store']['book'][1]['price']:	12.99
  /// $['store']['book'][2]['price']:	8.99
  /// $['store']['book'][3]['price']:	22.99
  /// $['store']['bicycle']['price']:	19.95
  prices
      .read(json)
      .map((match) => '${match.path}:\t${match.value}')
      .forEach(print);
}

Features and Limitations

This library follows the JsonPath internet draft specification. Since the spec itself is an evolving document, this implementation may lag behind, and some features may not be implemented in-full. Please refer to the tests (there are hundreds of them, including the CTS) to see what is supported.

Currently supported standard functions:

• length()
• count()
• match()
• search()
• value()

Data manipulation

Each JsonPathMatch produced by the .read() method contains the .pointer property which is a valid JSON Pointer and can be used to alter the referenced value. If you only need to manipulate JSON data, check out my JSON Pointer implementation.

User-defined functions

The JSONPath parser may be extended with user-defined functions. The user-defined functions take precedence over the built-in ones specified by the standard. Currently, only functions of 1 and 2 arguments are supported.

To create your own function:

1. Import package:json_path/fun_sdk.dart.
2. Create a class implementing either Fun1 (1 argument) or Fun2 (2 arguments).

To use it:

1. Create a new JsonPathParser with your function: final parser = JsonPathParser(functions: [MyFunction()]);
2. Use it to parse you expression: final jsonPath = parser.parse(r'$[?my_function(@)]');

For more details see the included example.

This package comes with some non-standard functions which you might find useful. To use them, import package:json_path/fun_extra.dart.

References

• Standard development
• Feature comparison matrix