This project is a C# implementation of JSONPath.
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.
Expressions of the underlying scripting language (<expr>) can be used as an
alternative to explicit names or indices, as in:
$.store.book[(@.length-1)].title
using the symbol @ for the current object. Filter expressions are supported via
the syntax ?(<boolean expr>), as in:
$.store.book[?(@.price < 10)].title
Below is a complete overview and a side-by-side comparison of the JSONPath syntax elements with its XPath counterparts:
| XPath | JSONPath | Description |
|---|---|---|
/ | $ | The root object/element |
. | @ | The current object/element |
/ | . or [] | Child operator |
.. | n/a | Parent operator |
// | .. | Recursive descent. JSONPath borrows this syntax from E4X. |
* | * | Wildcard. All objects/elements regardless their names. |
@ | n/a | Attribute access. JSON structures don't have attributes. |
[] | [] | Subscript operator. XPath uses it to iterate over element collections and for predicates. In Javascript and JSON it is the native array operator. |
| | [,] | Union operator in XPath results in a combination of node sets. JSONPath allows alternate names or array indices as a set. |
| n/a | [start:end:step] | Array slice operator borrowed from ES4. |
[] | ?() | Applies a filter (script) expression. |
| n/a | () | Script expression, using the underlying script engine. |
() | n/a | Grouping in XPath |
Let's practice JSONPath expressions by some more examples. We start with a simple JSON structure built after an XML example representing a bookstore:
{ "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
}
}
}
| XPath | JSONPath | Result | Notes |
|---|---|---|---|
/store/book/author | $.store.book[*].author | The authors of all books in the store | |
//author | $..author | All authors | |
/store/* | $.store.* | All things in store, which are some books and a red bicycle | |
/store//price | $.store..price | The price of everything in the store | |
//book[3] | $..book[2] | The third book | |
//book[last()] | $..book[(@.length-1)]$..book[-1:] | The last book in order | |
//book[position()<3] | $..book[0,1]$..book[:2] | The first two books | |
//book/*[self::category|self::author] or //book/(category,author) in XPath 2.0 | $..book[category,author] | The categories and authors of all books | |
//book[isbn] | $..book[?(@.isbn)] | Filter all books with isbn number | |
//book[price<10] | $..book[?(@.price<10)] | Filter all books cheapier than 10 | |
//*[price>19]/.. | $..[?(@.price>19)] | Categories with things more expensive than 19 | Parent (caret) not present in original spec |
//* | $..* | All elements in XML document; all members of JSON structure | |
/store/book/[position()!=1] | $.store.book[?(@path !== "$[\'store\'][\'book\'][0]")] | All books besides that at the path pointing to the first | @path not present in original spec |
See also: