JSONPath

JSONPath was developed by Stefan Goessner as an analog for XPath for use with JSON data. The following description is modified from his description of how JSONPath works.

JSONPath expressions always refer to a JSON structure in the same way as XPath expression are used in combination with an XML document. Since a JSON structure is usually anonymous and doesn't necessarily have a "root member object" JSONPath assumes the abstract name $ assigned to the outer level object.

JSONPath expressions can use the dot notation

$.store.book[0].title

or the bracket notation

$['store']['book'][0]['title']

for input paths. Internal or output paths will always be converted to the more general bracket notation.

JSONPath allows the wildcard symbol * for member names and array indices. It borrows the descendant operator '..' from E4X and the | array slice syntax proposal [start:end:step] from ECMASCRIPT 4 proposal.

KRL expressions (<expr>) can be used as an alternative to explicit names or indices using the symbol '@' for the current object. Filter expressions are supported via the syntax ?(<boolean expr>) as in

$.store.book[?(@.price < 10)].title

Comparison to XPath

Here is a complete overview and a side by side comparison of the JSONPath syntax elements with its XPath counterparts.

XPath has a lot more to offer (Location pathes in not abbreviated syntax, operators and functions) than listed here. Moreover there is a remarkable difference how the subscript operator works in Xpath and JSONPath.

• Square brackets in XPath expressions always operate on the node set resulting from the previous path fragment. Indices always start by 1.
• With JSONPath square brackets operate on the object or array addressed by the previous path fragment. Indices always start by 0.

Examples

The following provides example JSONPath expressions. The object is a simple JSON structure built after an XML example representing a bookstore (original XML file).

 { "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
    }
  }
}