getString (Function)
Function retrieves value specified in the given path of the JSON element as a string.
Syntax
<STRING> json:getString(<STRING|OBJECT> json, <STRING> path)
Query Parameters
| Name | Description | Default Value | Possible Data Types | Optional | Dynamic |
|---|---|---|---|---|---|
| json | The JSON input containing value. | STRING OBJECT | No | Yes | |
| path | The JSON path to fetch the value. | STRING | No | Yes |
Example 1
json:getString(json,'$.name')
In a JSON object like {'name' : 'John', 'age' : 23}, the function json:getString(json,'$.name') searches for a string value associated with the key name. Here, it returns John as there is a matching string at $.name.
Example 2
json:getString(json,'$.salary')
For a JSON object like {'name' : 'John', 'age' : 23}, the function json:getString(json,'$.salary') looks for a string value associated with the key salary. Here, it returns null as there is no matching element at $.salary.
Example 3
json:getString(json,'$.age')
In a JSON object like {'name' : 'John', 'age' : 23}, the function json:getString(json,'$.age') looks for a string value associated with the key age. Here, it returns "23" as a string, since the function can convert the numeric value at $.age to a string representation.
Example 4
json:getString(json,'$.address')
For a JSON object like {'name' : 'John', 'address' : {'city' : 'NY', 'country' : 'USA'}}, the function json:getString(json,'$.address') searches for a string associated with the key address. Here, it returns '{"city":"NY","country":"USA"}' as a string, since the function can convert the nested JSON object at $.address into a string representation.
Example 5
CREATE STREAM UserDetailsStream (json string);
CREATE SINK STREAM NameStream (name string);
@info(name = 'ExtractNameFromJson')
INSERT INTO NameStream
SELECT json:getString(json, '$.name') AS name
FROM UserDetailsStream;
In this example, two streams are defined: UserDetailsStream for input data and NameStream for output. The ExtractNameFromJson stream worker listens for events from the UserDetailsStream. Each event is a JSON string representing a user's details. The function json:getString(json, '$.name') is used to extract the name (a string) from each JSON string. This extracted name is then inserted into the NameStream. The stream worker continuously processes each user's details from UserDetailsStream, extracts the name, and feeds this value into the NameStream. This setup enables real-time analysis of the names of the users in the incoming data stream.