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JSON Path

The JSON-PATH directive uses a DSL for reading JSON records.

Syntax

json-path <source-column> <destination-column> <expression>
  • <source-column> specifies the column in the record that should be considered as the "root member object" or "$"
  • <destination-column> is the name of the output column in the record where the results of the expression will be stored
  • <expression> is a JSON path expression; see Usage Notes below for details

Usage Notes

An expression always refers to a JSON structure in the same way that an XPath expression is used in combination with an XML document. The "root member object" is always referred to as $ regardless if it is an object or an array.

Notation

Expressions can use either the "dot–notation":

$.name.first

or the "bracket–notation":

$['name']['first']

Operators

Operator Description
$ 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; must evaluate to a boolean value

Functions

Functions can be invoked at the tail end of a path: the input to a function is the output of the path expression. The function output is dictated by the function itself.

Function Returns Output
min() The min value of an array of numbers Double
max() The max value of an array of numbers Double
avg() The average value of an array of numbers Double
stddev() The standard deviation value of an array of numbers Double
length() The length of an array Integer

Filter Operators

Filters are logical expressions used to filter arrays. A typical filter would be:

[?(@.age>18)]

where @ represents the current item being processed.

  • More complex filters can be created with the logical operators && and ||

  • String literals must be enclosed by either single or double quotes, such as in [?(@.color=='blue')] or [?(@.color=="blue")]

Filter Operator Description
== Left is equal in type and value to right (note 1 is not equal to '1')
!= Left is not equal to right
< Left is less than right
<= Left is less than or equal to right
> Left is greater than right
>= Left is greater than or equal to right
=~ Left matches regular expression [?(@.name=~/foo.*?/i)]
in Left exists in right [?(@.size in ['S', 'M'])]
nin Left does not exist in right
size Size of left (array or string) matches right
empty Left (array or string) is empty

Examples

Using this record as an example:

{
    "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
}
JSON Path (click link to test) Result
$.store.book[*].author The authors of all books
$..author All authors
$.store.* All things, both books and bicycles
$.store..price The price of everything
$..book[2] The third book
$..book[0,1] The first two books
$..book[:2] All books from index 0 (inclusive) until index 2 (exclusive)
$..book[1:2] All books from index 1 (inclusive) until index 2 (exclusive)
$..book[-2:] Last two books
$..book[2:] Book number two from tail
$..book[?(@.isbn)] All books with an ISBN number
$..book[?(@.isbn)] All books with an ISBN number
$.store.book[?(@.price<10)] All books in store cheaper than 10
$..book[?(@.price<=$['expensive'])] All books in store that are not "expensive"
$..book[?(@.author=~/.*REES/i)] All books matching a regex (ignore case)
$..* All books
$..book.length() The number of books