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	/*
	* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package jdk.jfr;

	import java.lang.invoke.MethodHandle;
	import java.lang.invoke.MethodHandles;
	import java.util.ArrayList;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Objects;
	import java.util.Set;

	import jdk.jfr.internal.EventClassBuilder;
	import jdk.jfr.internal.JVMSupport;
	import jdk.jfr.internal.MetadataRepository;
	import jdk.jfr.internal.Type;
	import jdk.jfr.internal.Utils;

	/**
	* Class for defining an event at runtime.
	* <p>
	* 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}.
	* <p>
	* To define an event at compile time, see {@link Event}.
	* <p>
	* The following example shows how to implement a dynamic {@code Event} class.
	*
	* <pre>
	* {@code
	* 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();
	* }
	* </pre>
	*
	* @since 8
	*/
	public final class EventFactory {

	private static final long REGISTERED_ID = Type.getTypeId(Registered.class);

	private final Class<? extends Event> eventClass;
	private final MethodHandle constructorHandle;
	private final List<AnnotationElement> sanitizedAnnotation;
	private final List<ValueDescriptor> sanitizedFields;

	private EventFactory(Class<? extends Event> eventClass, List<AnnotationElement> sanitizedAnnotation, List<ValueDescriptor> sanitizedFields) throws IllegalAccessException, NoSuchMethodException, SecurityException {
	this.constructorHandle = MethodHandles.lookup().unreflectConstructor(eventClass.getConstructor());
	this.eventClass = eventClass;
	this.sanitizedAnnotation = sanitizedAnnotation;
	this.sanitizedFields = sanitizedFields;
	}

	/**
	* Creates an {@code EventFactory} object.
	* <p>
	* 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<AnnotationElement> annotationElements, List<ValueDescriptor> fields) {
	Objects.requireNonNull(fields);
	Objects.requireNonNull(annotationElements);
	JVMSupport.ensureWithInternalError();

	Utils.checkRegisterPermission();

	List<AnnotationElement> sanitizedAnnotation = Utils.sanitizeNullFreeList(annotationElements, AnnotationElement.class);
	List<ValueDescriptor> sanitizedFields = Utils.sanitizeNullFreeList(fields, ValueDescriptor.class);
	Set<String> nameSet = new HashSet<>();
	for (ValueDescriptor v : sanitizedFields) {
	String name = v.getName();
	if (v.isArray()) {
	throw new IllegalArgumentException("Array types are not allowed for fields");
	}
	if (!Type.isValidJavaFieldType(v.getTypeName())) {
	throw new IllegalArgumentException(v.getTypeName() + " is not a valid type for an event field");
	}
	if (!Type.isValidJavaIdentifier(v.getName())) {
	throw new IllegalArgumentException(name + " is not a valid name for an event field");
	}
	if (nameSet.contains(name)) {
	throw new IllegalArgumentException("Name of fields must be unique. Found two instances of " + name);
	}
	nameSet.add(name);
	}

	// Prevent event from being registered in <clinit>
	// and only use annotations that can be resolved (those in boot class loader)
	boolean needRegister = true;
	List<AnnotationElement> bootAnnotations = new ArrayList<>();
	for (AnnotationElement ae : sanitizedAnnotation) {
	long id = ae.getTypeId();
	if (ae.isInBoot()) {
	if (id == REGISTERED_ID) {
	if (Boolean.FALSE.equals(ae.getValue("value"))) {
	needRegister = false;
	}
	} else {
	bootAnnotations.add(ae);
	}
	}
	}
	bootAnnotations.add(new AnnotationElement(Registered.class, false));

	EventClassBuilder ecb = new EventClassBuilder(bootAnnotations, sanitizedFields);
	Class<? extends Event> eventClass = ecb.build();

	if (needRegister) {
	MetadataRepository.getInstance().register(eventClass, sanitizedAnnotation, sanitizedFields);
	}
	try {
	return new EventFactory(eventClass, sanitizedAnnotation, sanitizedFields);
	} catch (IllegalAccessException e) {
	throw new IllegalAccessError("Could not accees constructor of generated event handler, " + e.getMessage());
	} catch (NoSuchMethodException e) {
	throw new InternalError("Could not find constructor in generated event handler, " + e.getMessage());
	}
	}

	/**
	* Instantiates an event, so it can be populated with data and written to the
	* Flight Recorder system.
	* <p>
	* 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.
	* <p>
	* 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.
	* <p>
	* A registered event class can write data to Flight Recorder and event metadata
	* can be obtained by invoking {@link FlightRecorder#getEventTypes()}.
	* <p>
	* 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.
	* <p>
	* A unregistered event class can't write data to Flight Recorder and event
	* metadata can't be obtained by invoking
	* {@link FlightRecorder#getEventTypes()}.
	* <p>
	* 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);
	}

	}

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