Subscribing to Events From Event Provider Classes

To receive events from event provider classes, a listener must subscribe to the events. Subscribing to events also specifies the provider and the type of events that the listener will receive.

To subscribe to events from event provider classes, write one method in your listener class to process each type of event. To specify the provider and the type of event, annotate the method with the org.glassfish.external.probe.provider.annotations.ProbeListener annotation. In the @ProbeListener annotation, specify the provider and the type as follows:

"module-providername:module-name:probe-provider-name:event-type"

module-providername

The application to which the event provider belongs. This parameter must be the value of the moduleProviderName element or attribute in the definition of the event provider. See Defining an Event Provider by Writing a Java Class and Defining an Event Provider by Writing an XML Fragment.

module-name

The module for which the event provider is defined. This parameter must match be the value of the moduleName element or attribute in the definition of the event provider . See Defining an Event Provider by Writing a Java Class and Defining an Event Provider by Writing an XML Fragment.

probe-provider-name

The name of the event provider. This parameter must match be the value of the probeProviderName element or attribute in the definition of the event provider. See Defining an Event Provider by Writing a Java Class and Defining an Event Provider by Writing an XML Fragment.

event-type

The type of the event. This type is defined in the event provider class. For more information, see Defining Event Types in an Event Provider Class.

Annotate each parameter in the method signature with the @ProbeParam annotation. Set the value element of the @ProbeParam annotation to the name of the parameter.

In the method body, provide the code to update monitoring statistics in response to the event.

Example 5–6 Subscribing to Events From Event Provider Classes

This example shows the code for subscribing to events of type begin from the tx component. The provider of the component is TxManager. The body of the begin method contains code to increase the transaction count txcount by 1 each time that an event is received.

The definition of the begin event type is shown in Example 5–1.

The code for sending begin events is shown in Example 5–4.

The instantiation of the txCount object is shown in Example 5–5.

...
import org.glassfish.external.probe.provider.annotations.ProbeListener;
import org.glassfish.external.probe.provider.annotations.ProbeParam;
import org.glassfish.gmbal.ManagedObject;
...
@ManagedObject
public class TxListener {
    ...;    @ProbeListner("examplecomponent:transaction:manager:begin")
    public void begin(
    @ProbeParam("{txId}")
    String txId) {
      txCount.increment();
    }
  }