Class EventFactory

java.lang.Object
jdk.jfr.EventFactory
public final class EventFactory extends Object
Class for defining an event at runtime.

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 false.

To define an event at compile time, see Event.

The following example shows how to implement a dynamic Event class. 

List<ValueDescriptor> fields = new ArrayList<>();
List<AnnotationElement> messageAnnotations = Collections.singletonList(new AnnotationElement(Label.class, "Message"));
fields.add(new ValueDescriptor(String.class, "message", messageAnnotations));
List<AnnotationElement> numberAnnotations = Collections.singletonList(new AnnotationElement(Label.class, "Number"));
fields.add(new ValueDescriptor(int.class, "number", numberAnnotations));

String[] category = { "Example", "Getting Started" };
List<AnnotationElement> 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

  • Method Summary

    Modifier and Type
    Method
    Description
    static EventFactory
    create(List<AnnotationElement> annotationElements, List<ValueDescriptor> fields)
    Creates an EventFactory object.
    EventType
    getEventType()
    Returns the event type that is associated with this event factory.
    Event
    newEvent()
    Instantiates an event, so it can be populated with data and written to the Flight Recorder system.
    void
    register()
    Registers an unregistered event.
    void
    unregister()
    Unregisters the event that is associated with this event factory.

    Methods declared in class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Creates and returns a copy of this object.
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    Finalization is deprecated and subject to removal in a future release.
    final Class<?>
    getClass()
    Returns the runtime class of this Object.
    int
    hashCode()
    Returns a hash code value for this object.
    final void
    notify()
    Wakes up a single thread that is waiting on this object's monitor.
    final void
    notifyAll()
    Wakes up all threads that are waiting on this object's monitor.
    String
    toString()
    Returns a string representation of the object.
    final void
    wait()
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
    final void
    wait(long timeoutMillis)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
    final void
    wait(long timeoutMillis, int nanos)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

  • Method Details

    • create

      public static EventFactory create(List<AnnotationElement> annotationElements, List<ValueDescriptor> fields)
      Creates an EventFactory object.

      The order of the value descriptors specifies the index to use when setting event values.

      Parameters:
      annotationElements - list of annotation elements that describes the annotations on the event, not null
      fields - list of descriptors that describes the fields of the event, not null
      Returns:
      event factory, not 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.
      See Also:

    • newEvent

      public Event newEvent()
      Instantiates an event, so it can be populated with data and written to the Flight Recorder system.

      Use the Event.set(int, Object) method to set a value.

      Returns:
      an event instance, not null

    • getEventType

      public EventType getEventType()
      Returns the event type that is associated with this event factory.
      Returns:
      event type that is associated with this event factory, not null
      Throws:
      IllegalStateException - if the event factory is created with the Registered(false) annotation and the event class is not manually registered before the invocation of this method

    • register

      public void register()
      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 Registered annotation.

      A registered event class can write data to Flight Recorder and event metadata can be obtained by invoking FlightRecorder.getEventTypes().

      If the event class associated with this event factory is already registered, the call to this method is ignored.

      See Also:

    • unregister

      public void unregister()
      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 FlightRecorder.getEventTypes().

      If the event class associated with this event factory is not already registered, the call to this method is ignored.

      See Also: