+ * 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 REGISTERED_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);
+ }
+
+}