public final class EventFactory extends Object
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();
Modifier and Type | Method | Description |
---|---|---|
static EventFactory |
create |
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. |
public static EventFactory create(List<AnnotationElement> annotationElements, List<ValueDescriptor> fields)
EventFactory
object. The order of the value descriptors specifies the index to use when setting event values.
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
null
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.SecurityException
- if a security manager exists and the caller does not have FlightRecorderPermission("registerEvent")
public Event newEvent()
Use the Event.set(int, Object)
method to set a value.
null
public EventType getEventType()
null
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 methodpublic void register()
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.
SecurityException
- if a security manager exists and the caller does not have FlightRecorderPermission("registerEvent")
public void unregister()
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.
SecurityException
- if a security manager exists and the caller does not have FlightRecorderPermission("registerEvent")
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/jdk.jfr/jdk/jfr/EventFactory.html