getObject (Function)

Function retrieves the object specified in the given path of the JSON element.

Syntax

<OBJECT> json:getObject(<STRING|OBJECT> json, <STRING> path)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
json	The JSON input containing the object.		STRING OBJECT	No	Yes
path	The JSON path to fetch the object.		STRING	No	Yes

Example 1

@info(name = 'query1')
json:getObject(json,'$.address')

Given a JSON object like {'name' : 'John', 'address' : {'city' : 'NY', 'country' : 'USA'}}, the function json:getObject(json,'$.address') searches for a JSON object associated with the key address. In this case, it returns {'city' : 'NY', 'country' : 'USA'} as there is a matching object at $.address.

Example 2

@info(name = 'query2')
json:getObject(json,'$.age')

Given a JSON object like {'name' : 'John', 'age' : 23}, the function json:getObject(json,'$.age') attempts to retrieve a JSON object associated with the key age. However, it returns null because the value at $.age is not a JSON object, it's an integer.

Example 3

@info(name = 'query3')
json:getObject(json,'$.salary')

Given a JSON object like {'name' : 'John', 'age' : 23}, the function json:getObject(json,'$.salary') attempts to retrieve a JSON object associated with the key salary. In this case, it returns null as there is no matching element at $.salary.

Example 4

CREATE STREAM PersonStream (json string);
CREATE SINK STREAM AddressStream (name string, city string, country string);

@info(name = 'ExtractAddress')
INSERT INTO AddressStream
SELECT json:getString(json, '$.name') AS name, 
       json:getString(json:getObject(json, '$.address'), '$.city') AS city, 
       json:getString(json:getObject(json, '$.address'), '$.country') AS country
FROM PersonStream;

In this example, two streams are defined: PersonStream for input and AddressStream for output.

The ExtractAddress query listens for events from the PersonStream. Each event is a JSON string representing a person's details.

The function json:getString(json, '$.name') is used to extract the name (a string) from each JSON string. The functions json:getString(json:getObject(json, '$.address'), '$.city') and json:getString(json:getObject(json, '$.address'), '$.country') are used to extract the city and country from the nested address object.

These extracted values are then inserted into the AddressStream.

The query continuously processes each person's details from PersonStream, extracts the name, city, and country, and feeds these values into the AddressStream. This enables real-time analysis of the address details of the persons in the incoming data stream.