HHH-19535 test to demo relevant capabilities of new preMerge() interceptor

Author: gavinking

hibernate-core/src/test/java/org/hibernate/orm/test/interceptor/merge/MergeInterceptionTest.java

@@ -0,0 +1,62 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.interceptor.merge;
+
+import jakarta.persistence.ElementCollection;
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.Id;
+import org.hibernate.Hibernate;
+import org.hibernate.cfg.SessionEventSettings;
+import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.Jpa;
+import org.hibernate.testing.orm.junit.Setting;
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+@Jpa(annotatedClasses = MergeInterceptionTest.Thing.class,
+	integrationSettings = @Setting(name = SessionEventSettings.INTERCEPTOR,
+			value = "org.hibernate.orm.test.interceptor.merge.MergeInterceptor"))
+class MergeInterceptionTest {
+	@Test
+	void test(EntityManagerFactoryScope scope) {
+		Thing t = scope.fromTransaction( em -> {
+			Thing thing = new Thing();
+			thing.name = "Hibernate";
+			assertNull( thing.names );
+			em.persist( thing );
+			assertNotNull( thing.names );
+			assertTrue( Hibernate.isInitialized( thing.names ) );
+			assertEquals( 0, thing.names.size() );
+			thing.names.add( "CDI" );
+			thing.names.add( "Ceylon" );
+			return thing;
+		} );
+		scope.inTransaction( em -> {
+			t.name = "Hibernate ORM";
+			t.names = null;
+			Thing thing = em.merge( t );
+			assertNull( t.names );
+			assertNotNull( thing.names );
+			assertFalse( Hibernate.isInitialized( thing.names ) );
+			assertEquals( 2, thing.names.size() );
+		} );
+	}
+	@Entity
+	static class Thing {
+		@Id @GeneratedValue
+		private Long id;
+		private String name;
+		@ElementCollection
+		Set<String> names;
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/interceptor/merge/MergeInterceptor.java

@@ -0,0 +1,38 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.interceptor.merge;
+
+import org.hibernate.Hibernate;
+import org.hibernate.Interceptor;
+import org.hibernate.type.Type;
+
+/**
+ * An interceptor that initializes null collection references
+ * when an entity is passed to persist() or merge().
+ *
+ * @author Gavin King
+ */
+public class MergeInterceptor implements Interceptor {
+	@Override
+	public boolean onPersist(Object entity, Object id, Object[] state, String[] propertyNames, Type[] types) {
+		boolean result = false;
+		for ( int i = 0; i < types.length; i++ ) {
+			if ( types[i].isCollectionType() && state[i] == null ) {
+				state[i] = Hibernate.set().createNewInstance();
+				result = true;
+			}
+		}
+		return result;
+	}
+
+	@Override
+	public void preMerge(Object entity, Object[] state, String[] propertyNames, Type[] types) {
+		for ( int i = 0; i < types.length; i++ ) {
+			if ( types[i].isCollectionType() && state[i] == null ) {
+				state[i] = Hibernate.set().createDetachedInstance();
+			}
+		}
+	}
+}