- TIBCO BusinessEvents®
- CEP Query
- Query
- Callback

# Query.Callback.exists()

## Signature

`boolean exists(String listenerName)`

## Domain

ACTION, CONDITION

## Description

Checks if a listener with the given name exists.

## Parameters

Name | Type | Description
--- | --- | ---
`listenerName` | `String` | name of the listener.

## Returns

Type | Description
--- | ---
`boolean` | true if a listener by that name exists.

## Cautions

none