HHH-9339 - java.lang.Optional support

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

@@ -7,6 +7,7 @@
 package org.hibernate;
 
 import java.io.Serializable;
+import java.util.Optional;
 
 /**
  * Loads an entity by its primary identifier.
@@ -57,4 +58,14 @@ public interface IdentifierLoadAccess<T> {
 	 * @return The persistent instance or {@code null}
 	 */
 	T load(Serializable id);
+
+	/**
+	 * Same semantic as {@link #load} except that here {@link Optional} is returned to
+	 * handle nullability.
+	 *
+	 * @param id The identifier
+	 *
+	 * @return The persistent instance, if one, wrapped in Optional
+	 */
+	Optional<T> loadOptional(Serializable id);
 }

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

@@ -26,6 +26,7 @@ import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import javax.persistence.CacheRetrieveMode;
 import javax.persistence.CacheStoreMode;
@@ -2732,6 +2733,11 @@ public final class SessionImpl
 			}
 		}
 
+		@Override
+		public Optional<T> loadOptional(Serializable id) {
+			return Optional.ofNullable( load( id ) );
+		}
+
 		@SuppressWarnings("unchecked")
 		protected final T doLoad(Serializable id) {
 			if ( this.lockOptions != null ) {

hibernate-core/src/main/java/org/hibernate/query/Query.java

@@ -12,6 +12,7 @@ import java.time.OffsetDateTime;
 import java.time.ZonedDateTime;
 import java.util.Calendar;
 import java.util.Date;
+import java.util.Optional;
 import java.util.stream.Stream;
 import javax.persistence.FlushModeType;
 import javax.persistence.LockModeType;
@@ -57,6 +58,8 @@ public interface Query<R> extends TypedQuery<R>, org.hibernate.Query<R>, CommonQ
 	 */
 	RowSelection getQueryOptions();
 
+	Optional<R> uniqueResultOptional();
+
 	/**
 	 * Retrieve a Stream over the query results.
 	 * <p/>

hibernate-core/src/main/java/org/hibernate/query/internal/AbstractProducedQuery.java

@@ -21,6 +21,7 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.Spliterator;
 import java.util.Spliterators;
@@ -1325,6 +1326,11 @@ public abstract class AbstractProducedQuery<R> implements QueryImplementor<R> {
 		return stream;
 	}
 
+	@Override
+	public Optional<R> uniqueResultOptional() {
+		return Optional.ofNullable( uniqueResult() );
+	}
+
 	@Override
 	public List<R> list() {
 		beforeQuery();

hibernate-core/src/test/java/org/hibernate/test/ops/genericApi/BasicGetLoadAccessTest.java

@@ -6,6 +6,8 @@
  */
 package org.hibernate.test.ops.genericApi;
 
+import java.util.NoSuchElementException;
+import java.util.Optional;
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
@@ -20,6 +22,11 @@ import org.hibernate.boot.MetadataSources;
 import org.hibernate.testing.junit4.BaseNonConfigCoreFunctionalTestCase;
 import org.junit.Test;
 
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.fail;
+
 /**
  * @author Steve Ebersole
  */
@@ -138,4 +145,50 @@ public class BasicGetLoadAccessTest extends BaseNonConfigCoreFunctionalTestCase
 		s.getTransaction().commit();
 		s.close();
 	}
+
+	@Test
+	public void testNullLoadResult() {
+		Session s = openSession();
+		s.beginTransaction();
+
+		assertNull( s.byId( User.class ).load( -1 ) );
+
+		Optional<User> user = s.byId( User.class ).loadOptional( -1 );
+		assertNotNull( user );
+		assertFalse( user.isPresent() );
+		try {
+			user.get();
+			fail( "Expecting call to Optional#get to throw NoSuchElementException" );
+		}
+		catch (NoSuchElementException expected) {
+			// the expected result...
+		}
+
+		s.getTransaction().commit();
+		s.close();
+
+	}
+
+	@Test
+	public void testNullQueryResult() {
+		Session s = openSession();
+		s.beginTransaction();
+
+		assertNull( s.createQuery( "select u from User u where u.id = -1" ).uniqueResult() );
+
+		Optional<User> user = s.createQuery( "select u from User u where u.id = -1" ).uniqueResultOptional();
+		assertNotNull( user );
+		assertFalse( user.isPresent() );
+		try {
+			user.get();
+			fail( "Expecting call to Optional#get to throw NoSuchElementException" );
+		}
+		catch (NoSuchElementException expected) {
+			// the expected result...
+		}
+
+		s.getTransaction().commit();
+		s.close();
+
+	}
 }