JSON with JSONPath

JSONPath is a query language for JSON with features similar to XPath for XML. JSONPath is used for selecting and extracting a sub-section from the JSON document.

1. JSONPath Dependencies

To use JSONPath, we will need to include its dependency and then use it.

2. JSONPath Syntax

A JsonPath expression begins with the dollar sign ($) character, which refers to the root element of a query. The dollar sign is followed by a sequence of child elements, which are separated via dot (code) notation or via the square brackets (code).

The important JSONPath syntax rules are:

• $ symbol refers to the root object or element.
• @ symbol refers to the current object or element.
• . operator is the dot-child operator, which you use to denote a child element of the current element.
• [ ] is the subscript operator, which you use to denote a child element of the current element (by name or index).
• * operator is a wildcard, returning all objects or elements regardless of their names.
• , operator is the union operator, which returns the union of the children or indexes indicated.
• : operator is the array slice operator, so you can slice collections using the syntax [start:end:step] to return a subcollection of a collection.
• ( ) operator lets you pass a script expression in the underlying implementation’s script language. It’s not supported by every implementation of JSONPath, however.
• ? ( ) to query all items that meet a certain criteria.

3. JSONPath Expression Examples

Below given are few examples of JSONPath.

$.store.book[0].title
$.store.book[*].title
$..book[3]

//or using brackets

$['store']['book'][0].['title']
$['store']['book'][*].['title']
$..['book'][3]

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

4. JSONPath Example using JavaScript

We have the following JSON document. We will apply the JSONPath expressions to it.

{ 
	"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
		}
	}
}

Example 1

Using JSONPath to find the names of all authors.

var response = jsonPath(store , "$..author").toJSONString();

Program output:

[
"Nigel Rees",
"Evelyn Waugh",
"Herman Melville",
"J. R. R. Tolkien"
]

Example 2

Using JSONPath to find the details for book number 4. The array index is zero-based.

var response = jsonPath(store , "$..book[3]").toJSONString();

Program output:

[
	{
		"category":"fiction",
		"author":"J. R. R. Tolkien",
		"title":"The Lord of the Rings",
		"isbn":"0-395-19395-8",
		"price":22.99
	}
]