* It's highly recommended that the event is defined at compile time, if the * field layout is known, so the Java Virtual Machine (JVM) can optimize the * code, possibly remove all instrumentation if Flight Recorder is inactive or * if the enabled setting for this event is set to {@code false}. *
* To define an event at compile time, see {@link Event}. *
* The following example shows how to implement a dynamic {@code Event} class. * *
* {
* @code
* List fields = new ArrayList<>();
* List messageAnnotations = Collections.singletonList(new AnnotationElement(Label.class, "Message"));
* fields.add(new ValueDescriptor(String.class, "message", messageAnnotations));
* List numberAnnotations = Collections.singletonList(new AnnotationElement(Label.class, "Number"));
* fields.add(new ValueDescriptor(int.class, "number", numberAnnotations));
*
* String[] category = { "Example", "Getting Started" };
* List eventAnnotations = new ArrayList<>();
* eventAnnotations.add(new AnnotationElement(Name.class, "com.example.HelloWorld"));
* eventAnnotations.add(new AnnotationElement(Label.class, "Hello World"));
* eventAnnotations.add(new AnnotationElement(Description.class, "Helps programmer getting started"));
* eventAnnotations.add(new AnnotationElement(Category.class, category));
*
* EventFactory f = EventFactory.create(eventAnnotations, fields);
*
* Event event = f.newEvent();
* event.set(0, "hello, world!");
* event.set(1, 4711);
* event.commit();
* }
*
*
* @since 9
*/
public final class EventFactory {
private static final long REGSITERED_ID = Type.getTypeId(Registered.class);
private final Class eventClass;
private final MethodHandle constructorHandle;
private final List
* The order of the value descriptors specifies the index to use when setting
* event values.
*
* @param annotationElements list of annotation elements that describes the
* annotations on the event, not {@code null}
*
* @param fields list of descriptors that describes the fields of the event, not
* {@code null}
*
* @return event factory, not {@code null}
*
* @throws IllegalArgumentException if the input is not valid. For example,
* input might not be valid if the field type or name is not valid in
* the Java language or an annotation element references a type that
* can't be found.
*
* @throws SecurityException if a security manager exists and the caller does
* not have {@code FlightRecorderPermission("registerEvent")}
*
* @see Event#set(int, Object)
*/
public static EventFactory create(List
* Use the {@link Event#set(int, Object)} method to set a value.
*
* @return an event instance, not {@code null}
*/
public Event newEvent() {
try {
return (Event) constructorHandle.invoke();
} catch (Throwable e) {
throw new InstantiationError("Could not instantaite dynamically generated event class " + eventClass.getName() + ". " + e.getMessage());
}
}
/**
* Returns the event type that is associated with this event factory.
*
* @return event type that is associated with this event factory, not
* {@code null}
*
* @throws java.lang.IllegalStateException if the event factory is created with
* the {@code Registered(false)} annotation and the event class is not
* manually registered before the invocation of this method
*/
public EventType getEventType() {
return EventType.getEventType(eventClass);
}
/**
* Registers an unregistered event.
*
* By default, the event class associated with this event factory is registered
* when the event factory is created, unless the event has the
* {@link Registered} annotation.
*
* A registered event class can write data to Flight Recorder and event metadata
* can be obtained by invoking {@link FlightRecorder#getEventTypes()}.
*
* If the event class associated with this event factory is already registered,
* the call to this method is ignored.
*
* @throws SecurityException if a security manager exists and the caller
* does not have {@code FlightRecorderPermission("registerEvent")}
* @see Registered
* @see FlightRecorder#register(Class)
*/
public void register() {
MetadataRepository.getInstance().register(eventClass, sanitizedAnnotation, sanitizedFields);
}
/**
* Unregisters the event that is associated with this event factory.
*
* A unregistered event class can't write data to Flight Recorder and event
* metadata can't be obtained by invoking
* {@link FlightRecorder#getEventTypes()}.
*
* If the event class associated with this event factory is not already
* registered, the call to this method is ignored.
*
* @throws SecurityException if a security manager exists and the caller does
* not have {@code FlightRecorderPermission("registerEvent")}
* @see Registered
* @see FlightRecorder#unregister(Class)
*/
public void unregister() {
MetadataRepository.getInstance().unregister(eventClass);
}
}