HHH-17652 Fix NullPointerException when mapping audited many-to-one relationships

hibernate-envers/src/main/java/org/hibernate/envers/internal/synchronization/work/AbstractAuditWorkUnit.java

@@ -56,6 +56,8 @@ protected void fillDataWithId(Map<String, Object> data, Object revision) {
 
 		data.put( configuration.getRevisionTypePropertyName(), revisionType );
 		data.put( configuration.getOriginalIdPropertyName(), originalId );
+		// The $type$ property holds the name of the (versions) entity
+		data.put( "$type$", configuration.getAuditEntityName( entityName ) );
 	}
 
 	@Override

hibernate-envers/src/test/java/org/hibernate/orm/test/envers/integration/manytoone/bidirectional/ManyToOneCustomRevisionListenerTest.java

@@ -0,0 +1,204 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.envers.integration.manytoone.bidirectional;
+
+import jakarta.persistence.CascadeType;
+import jakarta.persistence.Entity;
+import jakarta.persistence.EntityManager;
+import jakarta.persistence.FetchType;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.Id;
+import jakarta.persistence.JoinColumn;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.OneToMany;
+import org.hibernate.envers.AuditReader;
+import org.hibernate.envers.Audited;
+import org.hibernate.envers.EntityTrackingRevisionListener;
+import org.hibernate.envers.RevisionEntity;
+import org.hibernate.envers.RevisionListener;
+import org.hibernate.envers.RevisionNumber;
+import org.hibernate.envers.RevisionTimestamp;
+import org.hibernate.envers.RevisionType;
+import org.hibernate.orm.test.envers.BaseEnversJPAFunctionalTestCase;
+import org.hibernate.orm.test.envers.Priority;
+import org.hibernate.testing.orm.junit.Jira;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@Jira( "https://hibernate.atlassian.net/browse/HHH-17652" )
+public class ManyToOneCustomRevisionListenerTest extends BaseEnversJPAFunctionalTestCase {
+	private static final ThreadLocal<AuditReader> auditReader = ThreadLocal.withInitial( () -> null );
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class[] {
+				Document.class,
+				DocumentAuthorEmployee.class,
+				Employee.class,
+				CustomRevisionEntity.class,
+		};
+	}
+
+	@Test
+	@Priority(10)
+	public void initData() {
+		// store in thread-local to use it in custom revision listener
+		auditReader.set( getAuditReader() );
+
+		EntityManager em = getEntityManager();
+		em.getTransaction().begin();
+
+		final Employee bilbo = new Employee( "Bilbo Baggins" );
+		em.persist( bilbo );
+		final Employee frodo = new Employee( "Frodo Baggins" );
+		em.persist( frodo );
+
+		em.getTransaction().commit();
+
+		em.getTransaction().begin();
+
+		final Document document = new Document( "The Hobbit" );
+		document.getAuthors().add( new DocumentAuthorEmployee( 1L, document, bilbo ) );
+		document.getAuthors().add( new DocumentAuthorEmployee( 2L, document, frodo ) );
+		em.persist( document );
+
+		em.getTransaction().commit();
+	}
+
+	@Test
+	public void testDocumentAuthorEmployeeRevisions() {
+		final AuditReader reader = getAuditReader();
+		assertLastRevision( reader, 1L, "Bilbo Baggins" );
+		assertLastRevision( reader, 2L, "Frodo Baggins" );
+		getEntityManager().close();
+	}
+
+	private static void assertLastRevision(AuditReader reader, Long id, String employee) {
+		final List<Number> revisions = reader.getRevisions( DocumentAuthorEmployee.class, id );
+		final Number revisionNumber = revisions.get( revisions.size() - 1 );
+		final DocumentAuthorEmployee result = reader.find( DocumentAuthorEmployee.class, id, revisionNumber );
+		assertThat( result.getEmployee().getName() ).isEqualTo( employee );
+		assertThat( result.getDocument().getTitle() ).isEqualTo( "The Hobbit" );
+	}
+
+	@Audited(withModifiedFlag = true)
+	@Entity(name = "Document")
+	static class Document {
+		@Id
+		@GeneratedValue
+		private Long id;
+
+		private String title;
+
+		@OneToMany(mappedBy = "document", cascade = CascadeType.ALL)
+		private List<DocumentAuthorEmployee> authors = new ArrayList<>();
+
+		public Document() {
+		}
+
+		public Document(String title) {
+			this.title = title;
+		}
+
+		public List<DocumentAuthorEmployee> getAuthors() {
+			return authors;
+		}
+
+		public String getTitle() {
+			return title;
+		}
+	}
+
+	@Audited(withModifiedFlag = true)
+	@Entity(name = "DocumentAuthorEmployee")
+	static class DocumentAuthorEmployee {
+		@Id
+		private Long id;
+
+		@ManyToOne
+		@JoinColumn(name = "document_id")
+		private Document document;
+
+		@ManyToOne(fetch = FetchType.EAGER)
+		@JoinColumn(name = "employee_id")
+		private Employee employee;
+
+		public DocumentAuthorEmployee() {
+		}
+
+		public DocumentAuthorEmployee(Long id, Document document, Employee employee) {
+			this.id = id;
+			this.document = document;
+			this.employee = employee;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public Document getDocument() {
+			return document;
+		}
+
+		public Employee getEmployee() {
+			return employee;
+		}
+	}
+
+	@Audited(withModifiedFlag = true)
+	@Entity(name = "Employee")
+	static class Employee {
+		@Id
+		@GeneratedValue
+		private Long id;
+
+		private String name;
+
+		public Employee() {
+		}
+
+		public Employee(String name) {
+			this.name = name;
+		}
+
+		public String getName() {
+			return name;
+		}
+	}
+
+	@Entity(name = "CustomRevisionEntity")
+	@RevisionEntity(CustomRevisionListener.class)
+	static class CustomRevisionEntity {
+		@Id
+		@GeneratedValue
+		@RevisionNumber
+		private int id;
+
+		@RevisionTimestamp
+		private long timestamp;
+	}
+
+	static class CustomRevisionListener implements RevisionListener, EntityTrackingRevisionListener {
+		@SuppressWarnings({"unchecked", "rawtypes"})
+		@Override
+		public void entityChanged(Class entityClass, String entityName, Object entityId, RevisionType revisionType, Object revisionEntity) {
+			final AuditReader reader = auditReader.get();
+			final List<Number> revisions = reader.getRevisions( entityClass, entityId );
+			final Number revisionNumber = revisions.get( revisions.size() - 1 );
+
+			// This is what triggered the NPE
+			final Object obj = reader.find( entityClass, entityId, revisionNumber );
+			assertThat( obj ).isNotNull();
+		}
+
+		@Override
+		public void newRevision(Object revisionEntity) {
+		}
+	}
+}