HHH-18492 add Hibernate.isEmpty() for pure convenience

HHH-18492 add Hibernate.isEmpty() for pure convenience

Signed-off-by: Gavin King <gavin@hibernate.org>

hibernate-core/src/main/java/org/hibernate/Hibernate.java

@@ -190,6 +190,21 @@ public final class Hibernate {
 				: collection.size();
 	}
 
+	/**
+	 * Determine is the given persistent collection is {@linkplain Collection#isEmpty() empty},
+	 * without fetching its state from the database.
+	 *
+	 * @param collection a persistent collection associated with an open session
+	 * @return {@code true} if the collection is empty
+	 *
+	 * @since 7.0
+	 */
+	public static boolean isEmpty(Collection<?> collection) {
+		return collection instanceof PersistentCollection
+				? ((PersistentCollection<?>) collection).getSize() == 0
+				: collection.isEmpty();
+	}
+
 	/**
 	 * Determine if the given persistent collection {@linkplain Collection#contains(Object) contains}
 	 * the given element, without fetching its state from the database.

hibernate-core/src/main/java/org/hibernate/collection/spi/AbstractPersistentCollection.java

@@ -175,22 +175,24 @@ public abstract class AbstractPersistentCollection<E> implements Serializable, P
 		return false;
 	}
 
-	public int  getSize() {
+	public int getSize() {
 		if ( cachedSize>=0 ) {
 			return cachedSize;
 		}
-		final CollectionEntry entry = session.getPersistenceContextInternal().getCollectionEntry( this );
-		if ( entry == null ) {
-			throwLazyInitializationExceptionIfNotConnected();
-			throwLazyInitializationException("collection not associated with session");
-			throw new AssertionFailure("impossible");
-		}
 		else {
-			if ( hasQueuedOperations() ) {
+			final CollectionEntry entry = session.getPersistenceContextInternal().getCollectionEntry( this );
-				session.flush();
+			if ( entry == null ) {
+				throwLazyInitializationExceptionIfNotConnected();
+				throwLazyInitializationException("collection not associated with session");
+				throw new AssertionFailure("impossible");
+			}
+			else {
+				if ( hasQueuedOperations() ) {
+					session.flush();
+				}
+				cachedSize = entry.getLoadedPersister().getSize( entry.getLoadedKey(), session );
+				return cachedSize;
 			}
-			cachedSize = entry.getLoadedPersister().getSize( entry.getLoadedKey(), session );
-			return cachedSize;
 		}
 	}
 

hibernate-core/src/main/java/org/hibernate/persister/collection/AbstractCollectionPersister.java

@@ -1383,9 +1383,7 @@ public abstract class AbstractCollectionPersister
 	public int getSize(Object key, SharedSessionContractImplementor session) {
 		try {
 			final JdbcCoordinator jdbcCoordinator = session.getJdbcCoordinator();
-			PreparedStatement st = jdbcCoordinator
+			final PreparedStatement st = jdbcCoordinator.getStatementPreparer().prepareStatement( sqlSelectSizeString );
-					.getStatementPreparer()
-					.prepareStatement( sqlSelectSizeString );
 			try {
 				getKeyType().nullSafeSet( st, key, 1, session );
 				ResultSet rs = jdbcCoordinator.getResultSetReturn().extract( st, sqlSelectSizeString );