HHH-10302 Cache the LoadEvent and PostLoadEvent to reduce allocations

Author: stuartwdouglas

hibernate-core/src/main/java/org/hibernate/event/internal/DefaultLoadEventListener.java

@@ -615,7 +615,7 @@ protected Object loadFromSecondLevelCache(
 			}
 			else {
 				entity = convertCacheReferenceEntryToEntity( (ReferenceCacheEntryImpl) entry,
-						event.getEntityId(), persister, event.getSession(), entityKey );
+						event.getEntityId(), persister, event.getSession(), entityKey, event );
 			}
 		}
 		else {
@@ -638,7 +638,8 @@ private Object convertCacheReferenceEntryToEntity(
 			Serializable entityId,
 			EntityPersister persister,
 			EventSource session,
-			EntityKey entityKey) {
+			EntityKey entityKey,
+			LoadEvent loadEvent) {
 		final Object entity = referenceCacheEntry.getReference();
 
 		if ( entity == null ) {
@@ -651,15 +652,15 @@ private Object convertCacheReferenceEntryToEntity(
 			EventListenerGroup<PostLoadEventListener> evenListenerGroup = getEvenListenerGroup(session);
 
 			if(!evenListenerGroup.isEmpty()) {
-				postLoad(session, evenListenerGroup.listeners(), entity, entityId, persister);
+				postLoad(session, evenListenerGroup.listeners(), entity, entityId, persister, loadEvent);
 			}
 			return entity;
 		}
 	}
 
 	private void postLoad(EventSource session, Iterable<PostLoadEventListener> listeners,
-							Object entity, Serializable entityId, EntityPersister persister) {
-		PostLoadEvent postLoadEvent = new PostLoadEvent(session)
+							Object entity, Serializable entityId, EntityPersister persister, LoadEvent event) {
+		PostLoadEvent postLoadEvent = event.getPostLoadEvent()
 				.setEntity(entity)
 				.setId(entityId)
 				.setPersister(persister);
@@ -788,7 +789,7 @@ private Object convertCacheEntryToEntity(
 		persistenceContext.initializeNonLazyCollections();
 
 		//PostLoad is needed for EJB3
-		PostLoadEvent postLoadEvent = new PostLoadEvent( session )
+		PostLoadEvent postLoadEvent = event.getPostLoadEvent()
 				.setEntity( entity )
 				.setId( entityId )
 				.setPersister( persister );
@@ -885,7 +886,7 @@ private Object assembleCacheEntry(
 
 		//PostLoad is needed for EJB3
 		//TODO: reuse the PostLoadEvent...
-		PostLoadEvent postLoadEvent = new PostLoadEvent( session )
+		PostLoadEvent postLoadEvent = event.getPostLoadEvent()
 				.setEntity( result )
 				.setId( id )
 				.setPersister( persister );

hibernate-core/src/main/java/org/hibernate/event/spi/LoadEvent.java

@@ -45,6 +45,7 @@ public LockOptions setScope(boolean scope) {
 	private LockOptions lockOptions;
 	private boolean isAssociationFetch;
 	private Object result;
+	private PostLoadEvent postLoadEvent;
 
 	public LoadEvent(Serializable entityId, Object instanceToLoad, EventSource source) {
 		this( entityId, null, instanceToLoad, DEFAULT_LOCK_OPTIONS, false, source );
@@ -104,6 +105,7 @@ else if ( lockOptions.getLockMode() == null ) {
 		this.instanceToLoad = instanceToLoad;
 		this.lockOptions = lockOptions;
 		this.isAssociationFetch = isAssociationFetch;
+		this.postLoadEvent = new PostLoadEvent(source);
 	}
 
 	public Serializable getEntityId() {
@@ -180,4 +182,12 @@ public Object getResult() {
 	public void setResult(Object result) {
 		this.result = result;
 	}
+
+	public PostLoadEvent getPostLoadEvent() {
+		return postLoadEvent;
+	}
+
+	public void setPostLoadEvent(PostLoadEvent postLoadEvent) {
+		this.postLoadEvent = postLoadEvent;
+	}
 }

hibernate-core/src/main/java/org/hibernate/internal/SessionImpl.java

@@ -205,6 +205,7 @@ public final class SessionImpl extends AbstractSessionImpl implements EventSourc
 	private transient ExceptionMapper exceptionMapper;
 	private transient ManagedFlushChecker managedFlushChecker;
 	private transient AfterCompletionAction afterCompletionAction;
+	private transient LoadEvent loadEvent; //cached LoadEvent instance
 
 	/**
 	 * Constructor used for openSession(...) processing, as well as construction
@@ -936,8 +937,26 @@ private void fireDelete(DeleteEvent event, Set transientEntities) {
 
 	@Override
 	public void load(Object object, Serializable id) throws HibernateException {
-		LoadEvent event = new LoadEvent( id, object, this );
+		LoadEvent event = loadEvent;
+		loadEvent = null;
+		if(event == null) {
+			event = new LoadEvent( id, object, this );
+		} else {
+			event.setEntityClassName(null);
+			event.setEntityId(id);
+			event.setInstanceToLoad(object);
+			event.setLockMode(LoadEvent.DEFAULT_LOCK_MODE);
+			event.setLockScope(LoadEvent.DEFAULT_LOCK_OPTIONS.getScope());
+			event.setLockTimeout(LoadEvent.DEFAULT_LOCK_OPTIONS.getTimeOut());
+		}
 		fireLoad( event, LoadEventListener.RELOAD );
+		if(loadEvent == null) {
+			event.setEntityClassName(null);
+			event.setEntityId(null);
+			event.setInstanceToLoad(null);
+			event.setResult(null);
+			loadEvent = event;
+		}
 	}
 
 	@Override
@@ -971,10 +990,28 @@ public Object immediateLoad(String entityName, Serializable id) throws Hibernate
 			EntityPersister persister = getFactory().getEntityPersister( entityName );
 			LOG.debugf( "Initializing proxy: %s", MessageHelper.infoString( persister, id, getFactory() ) );
 		}
-
-		LoadEvent event = new LoadEvent( id, entityName, true, this );
+		LoadEvent event = loadEvent;
+		loadEvent = null;
+		if(event == null) {
+			event = new LoadEvent( id, entityName, true, this );
+		} else {
+			event.setEntityClassName(entityName);
+			event.setEntityId(id);
+			event.setInstanceToLoad(null);
+			event.setLockMode(LoadEvent.DEFAULT_LOCK_MODE);
+			event.setLockScope(LoadEvent.DEFAULT_LOCK_OPTIONS.getScope());
+			event.setLockTimeout(LoadEvent.DEFAULT_LOCK_OPTIONS.getTimeOut());
+		}
 		fireLoad( event, LoadEventListener.IMMEDIATE_LOAD );
-		return event.getResult();
+		Object result = event.getResult();
+		if(loadEvent == null) {
+			event.setEntityClassName(null);
+			event.setEntityId(null);
+			event.setInstanceToLoad(null);
+			event.setResult(null);
+			loadEvent = event;
+		}
+		return result;
 	}
 
 	@Override
@@ -986,12 +1023,32 @@ public Object internalLoad(String entityName, Serializable id, boolean eager, bo
 				: eager
 				? LoadEventListener.INTERNAL_LOAD_EAGER
 				: LoadEventListener.INTERNAL_LOAD_LAZY;
-		LoadEvent event = new LoadEvent( id, entityName, true, this );
+
+		LoadEvent event = loadEvent;
+		loadEvent = null;
+		if(event == null) {
+			event = new LoadEvent( id, entityName, true, this );
+		} else {
+			event.setEntityClassName(entityName);
+			event.setEntityId(id);
+			event.setInstanceToLoad(null);
+			event.setLockMode(LoadEvent.DEFAULT_LOCK_MODE);
+			event.setLockScope(LoadEvent.DEFAULT_LOCK_OPTIONS.getScope());
+			event.setLockTimeout(LoadEvent.DEFAULT_LOCK_OPTIONS.getTimeOut());
+		}
 		fireLoad( event, type );
+		Object result = event.getResult();
 		if ( !nullable ) {
-			UnresolvableObjectException.throwIfNull( event.getResult(), id, entityName );
+			UnresolvableObjectException.throwIfNull(result, id, entityName );
 		}
-		return event.getResult();
+		if(loadEvent == null) {
+			event.setEntityClassName(null);
+			event.setEntityId(null);
+			event.setInstanceToLoad(null);
+			event.setResult(null);
+			loadEvent = event;
+		}
+		return result;
 	}
 
 	@Override