isExists (Function)

Function checks whether there is a JSON element present in the given path or not.

Syntax

<BOOL> json:isExists(<STRING|OBJECT> json, <STRING> path)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
json	The JSON input that needs to be searched for an elements.		STRING OBJECT	No	Yes
path	The JSON path to check for the element.		STRING	No	Yes

Example 1

json:isExists(json, '$.name')

Given a JSON object like {'name' : 'John', 'age' : 23}, the function json:isExists(json,'$.name') checks if an element exists at the key name. In this instance, it returns true because there is a matching element at $.name.

Example 2

json:isExists(json, '$.salary')

With a JSON object like {'name' : 'John', 'age' : 23}, the function json:isExists(json,'$.salary') checks if an element exists at the key salary. In this instance, it returns false because there is no matching element at $.salary.

Example 3

json:isExists(json, '$.age')

Given a JSON object like {'name' : 'John', 'age' : 23}, the function json:isExists(json,'$.age') checks if an element exists at the key age. In this instance, it returns true because there is a matching element at $.age.

Example 4

json:isExists(json, '$.address.city')

For a JSON object like {'name' : 'John', 'address' : {'city' : 'NY', 'country' : 'USA'}}, the function json:isExists(json,'$.address.city') checks if an element exists at the key address.city. In this instance, it returns true because there is a matching element at $.address.city.

Example 5

CREATE STREAM PersonStream (json string);
CREATE SINK STREAM AddressExistsStream (name string, addressExists bool);

@info(name = 'ExtractAddressData')
INSERT INTO AddressExistsStream
SELECT json:getString(json, '$.name') AS name, 
       json:isExists(json, '$.address') AS addressExists
FROM PersonStream;

In this example, PersonStream is defined for the input data and AddressExistsStream for the output.

The ExtractAddressData stream worker listens for events from the PersonStream. Each event is a JSON string representing a person's details.

The function json:getString(json, '$.name') is used to extract the name (a string) from each JSON string. The function json:isExists(json, '$.address') is used to check if the address key exists in each JSON string.

The extracted name and the result of the existence check are then inserted into the AddressExistsStream.

The stream worker continuously processes each person's details from PersonStream, extracts the name, checks the existence of the address, and feeds these values into the AddressExistsStream. This allows real-time analysis of whether the address details of the persons in the incoming data stream exist or not.