HHH-12974 - Document @OnDelete behavior in regards to disabling the Persistence Context entity removal cascading event

documentation/src/main/asciidoc/userguide/chapters/pc/PersistenceContext.adoc

@@ -825,7 +825,7 @@ the automatic schema generator will apply the ON DELETE CASCADE SQL directive to
 as illustrated by the following example.
 
 [[pc-cascade-on-delete-mapping-example]]
-.`@OnDelete` mapping
+.`@OnDelete` `@ManyToOne` mapping
 ====
 [source, JAVA, indent=0]
 ----
@@ -843,10 +843,10 @@ include::{extrasdir}/pc-cascade-on-delete-mapping-example.sql[]
 ----
 ====
 
-Now, you can just remove the `Person` entity, and the associated `Phone` is going to be removed automatically.
+Now, you can just remove the `Person` entity, and the associated `Phone` entities are going to be deleted automatically via the Foreign Key cascade.
 
 [[pc-cascade-on-delete-example]]
-.`@OnDelete` example
+.`@OnDelete` `@ManyToOne` delete example
 ====
 [source, JAVA, indent=0]
 ----
@@ -857,4 +857,45 @@ include::{sourcedir}/CascadeOnDeleteTest.java[tags=pc-cascade-on-delete-example]
 ----
 include::{extrasdir}/pc-cascade-on-delete-example.sql[]
 ----
+====
+
+The `@OnDelete` annotation can also be placed on a collection, as
+illustrated in the following example.
+
+[[pc-cascade-on-delete-collection-mapping-example]]
+.`@OnDelete` `One@ToMany` mapping
+====
+[source, JAVA, indent=0]
+----
+include::{sourcedir}/CascadeOnDeleteCollectionTest.java[tags=pc-cascade-on-delete-collection-mapping-Person-example]
+----
+
+[source, JAVA, indent=0]
+----
+include::{sourcedir}/CascadeOnDeleteCollectionTest.java[tags=pc-cascade-on-delete-collection-mapping-Phone-example]
+----
+====
+
+Now, when removing the `Person` entity, all the associated `Phone` child entities are deleted via the Foreign Key cascade even if the `@OneToMany` collection was using the `CascadeType.ALL` attribute.
+
+[[pc-cascade-on-delete-collection-example]]
+.`@OnDelete` `@ManyToOne` delete example
+====
+[source, JAVA, indent=0]
+----
+include::{sourcedir}/CascadeOnDeleteCollectionTest.java[tags=pc-cascade-on-delete-collection-example]
+----
+
+[source, SQL, indent=0]
+----
+include::{extrasdir}/pc-cascade-on-delete-example.sql[]
+----
+====
+
+[NOTE]
+====
+Without the `@OnDelete` annotation, the `@OneToMany` association relies on the `cascade` attribute to propagate the `remove` entity state transition from the parent entity to its children.
+However, when the `@OnDelete` annotation is in place, Hibernate prevents the child entity `DELETE` statement from being executed while flushing the Persistence Context.
+
+This way, only the parent entity gets deleted, and all the associated child records are removed by the database engine, instead of being deleted explicitly via `DELETE` statements.
 ====

documentation/src/test/java/org/hibernate/userguide/pc/CascadeOnDeleteCollectionTest.java

@@ -0,0 +1,149 @@
+package org.hibernate.userguide.pc;
+
+import java.util.ArrayList;
+import java.util.List;
+import javax.persistence.CascadeType;
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.Id;
+import javax.persistence.ManyToOne;
+import javax.persistence.OneToMany;
+
+import org.hibernate.annotations.OnDelete;
+import org.hibernate.annotations.OnDeleteAction;
+import org.hibernate.jpa.test.BaseEntityManagerFunctionalTestCase;
+
+import org.junit.Test;
+
+import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
+
+/**
+ * @author Vlad Mihalcea
+ */
+public class CascadeOnDeleteCollectionTest extends BaseEntityManagerFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class<?>[] {
+				Person.class,
+				Phone.class
+		};
+	}
+
+	@Test
+	public void test() {
+		doInJPA( this::entityManagerFactory, entityManager -> {
+			Person person = new Person();
+			person.setId( 1L );
+			person.setName( "John Doe" );
+			entityManager.persist( person );
+
+			Phone phone1 = new Phone();
+			phone1.setId( 1L );
+			phone1.setNumber( "123-456-7890" );
+			phone1.setOwner( person );
+			person.addPhone( phone1 );
+
+			Phone phone2 = new Phone();
+			phone2.setId( 2L );
+			phone2.setNumber( "101-010-1234" );
+			phone2.setOwner( person );
+			person.addPhone( phone2 );
+		} );
+
+		doInJPA( this::entityManagerFactory, entityManager -> {
+			//tag::pc-cascade-on-delete-collection-example[]
+			Person person = entityManager.find( Person.class, 1L );
+			entityManager.remove( person );
+			//end::pc-cascade-on-delete-collection-example[]
+		} );
+
+	}
+
+	//tag::pc-cascade-on-delete-collection-mapping-Person-example[]
+	@Entity(name = "Person")
+	public static class Person {
+
+		@Id
+		private Long id;
+
+		private String name;
+
+		@OneToMany(mappedBy = "owner", cascade = CascadeType.ALL)
+		@OnDelete(action = OnDeleteAction.CASCADE)
+		private List<Phone> phones = new ArrayList<>();
+
+		//Getters and setters are omitted for brevity
+
+		//end::pc-cascade-on-delete-collection-mapping-Person-example[]
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+
+		public void addPhone(Phone phone) {
+			phone.setOwner( this );
+			phones.add( phone );
+		}
+
+		//tag::pc-cascade-on-delete-collection-mapping-Person-example[]
+	}
+	//end::pc-cascade-on-delete-collection-mapping-Person-example[]
+
+	//tag::pc-cascade-on-delete-collection-mapping-Phone-example[]
+	@Entity(name = "Phone")
+	public static class Phone {
+
+		@Id
+		private Long id;
+
+		@Column(name = "`number`")
+		private String number;
+
+		@ManyToOne(fetch = FetchType.LAZY)
+		private Person owner;
+
+		//Getters and setters are omitted for brevity
+
+		//end::pc-cascade-on-delete-collection-mapping-Phone-example[]
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getNumber() {
+			return number;
+		}
+
+		public void setNumber(String number) {
+			this.number = number;
+		}
+
+		public Person getOwner() {
+			return owner;
+		}
+
+		public void setOwner(Person owner) {
+			this.owner = owner;
+		}
+		//tag::pc-cascade-on-delete-collection-mapping-Phone-example[]
+	}
+	//end::pc-cascade-on-delete-collection-mapping-Phone-example[]
+}

hibernate-core/src/test/java/org/hibernate/id/IdClassManyToOneCascadeTest.java

@@ -19,7 +19,7 @@ import org.hibernate.testing.TestForIssue;
 import org.junit.Test;
 
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
-import static org.wildfly.common.Assert.assertTrue;
+import static org.junit.Assert.assertTrue;
 
 /**
  * @author Vlad Mihalcea

hibernate-core/src/test/java/org/hibernate/jpa/test/graphs/EntityGraphUsingFetchGraphForLazyTest.java

@@ -36,7 +36,7 @@ import org.jboss.logging.Logger;
 
 import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
 import static org.junit.Assert.assertTrue;
-import static org.wildfly.common.Assert.assertFalse;
+import static org.junit.Assert.assertFalse;
 
 /**
  * @author Vlad Mihalcea

hibernate-core/src/test/java/org/hibernate/jpa/test/schemagen/SchemaCreateDropUtf8WithoutHbm2DdlCharsetNameTest.java

@@ -26,7 +26,7 @@ import org.hibernate.testing.TestForIssue;
 import org.junit.Before;
 import org.junit.Test;
 
-import static org.wildfly.common.Assert.assertTrue;
+import static org.junit.Assert.assertTrue;
 
 /**
  * @author Vlad Mihalcea

hibernate-core/src/test/java/org/hibernate/test/collection/bag/PersistentBagContainsTest.java

@@ -21,7 +21,7 @@ import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
 import org.junit.Test;
 
 import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
-import static org.wildfly.common.Assert.assertTrue;
+import static org.junit.Assert.assertTrue;
 
 /**
  * Tests related to contains operations on a PersistentBag.

hibernate-core/src/test/java/org/hibernate/test/tm/AfterCompletionTest.java

@@ -31,7 +31,7 @@ import org.hibernate.testing.junit4.BaseNonConfigCoreFunctionalTestCase;
 
 import static org.hibernate.testing.junit4.ExtraAssertions.assertTyping;
 import static org.junit.Assert.assertEquals;
-import static org.wildfly.common.Assert.assertTrue;
+import static org.junit.Assert.assertTrue;
 
 /**
  * @author Chris Cranford