The on statement is used to create an event listener that looks for input events that match the pattern specified by an event condition. When a matching event is detected, the event listener fires (also referred to as triggers) and the specified event listener action is executed.

A listener assignment clause is used to obtain a reference to the event listener that is created by the on statement. One can either define a new variable of type listener or specify a reference to an existing listener variable.

Example:

The event condition specifies what events are of interest. See Event expressions.

A listener action defines the processing that will be performed when a matching event is detected and the event listener fires. The listener action can be one of the following:

The listener action is invoked automatically by the correlator when the event condition is satisfied. This may be:

For more information, see Specifying the on statement.