HHH-7573 Added check for handle LazyPropertyInitializer.UNFETCHED_PROPERTY

Added test to check that the change handles the various possible scenarios.
Test requires build time instrumentation.

hibernate-entitymanager/hibernate-entitymanager.gradle

@@ -110,3 +110,17 @@ configurations {
 artifacts {
     tests testJar
 }
+
+task instrument(dependsOn: compileTestJava) << {
+    ant.taskdef(name: 'hibInstrument',
+            classname: 'org.hibernate.tool.instrument.javassist.InstrumentTask',
+            classpath: configurations.testCompile.asPath)
+    ant.hibInstrument(verbose: 'true'){
+        fileset(dir:"$buildDir/classes/test/org/hibernate/jpa/test/callbacks/"){
+            include(name: "EntityWithLazyProperty.class")
+        }
+    }
+    println("hibernate instrumentation")
+}
+
+test.dependsOn instrument

hibernate-entitymanager/src/main/java/org/hibernate/jpa/event/internal/core/JpaFlushEntityEventListener.java

@@ -24,6 +24,7 @@
 package org.hibernate.jpa.event.internal.core;
 
 import org.hibernate.SessionFactory;
+import org.hibernate.bytecode.instrumentation.spi.LazyPropertyInitializer;
 import org.hibernate.engine.spi.EntityEntry;
 import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.Status;
@@ -78,7 +79,8 @@ public class JpaFlushEntityEventListener extends DefaultFlushEntityEventListener
 		int size = newState.length;
 		boolean isDirty = false;
 		for ( int index = 0; index < size ; index++ ) {
-			if ( !types[index].isEqual( state[index], newState[index] ) ) {
+			if (state[index] == LazyPropertyInitializer.UNFETCHED_PROPERTY && newState[index] != LazyPropertyInitializer.UNFETCHED_PROPERTY
+				|| state[index] != newState[index] && !types[index].isEqual(state[index], newState[index])) {
 				isDirty = true;
 				state[index] = newState[index];
 			}

hibernate-entitymanager/src/test/java/org/hibernate/jpa/test/callbacks/CallbacksTest.java

@@ -245,7 +245,76 @@ public class CallbacksTest extends BaseEntityManagerFunctionalTestCase {
 				RemoteControl.class,
 				Rythm.class,
 				Plant.class,
-				Kitten.class
+				Kitten.class,
+				EntityWithLazyProperty.class
 		};
 	}
+
+	/**
+	 * Test for HHH-7573.
+	 * Load some test data into an entity which has a lazy property and a @PreUpdate callback, then reload and update a
+	 * non lazy field which will trigger the PreUpdate lifecycle callback.
+	 * @throws Exception
+	 */
+	@Test
+	public void testJpaFlushEntityEventListener() throws Exception {
+		EntityWithLazyProperty entity;
+		EntityManager em = getOrCreateEntityManager();
+
+		byte[] testArray = new byte[]{0x2A};
+
+		//persist the test entity.
+		em.getTransaction().begin();
+		entity = new EntityWithLazyProperty();
+		entity.setSomeField("TEST");
+		entity.setLazyData(testArray);
+		em.persist(entity);
+		em.getTransaction().commit();
+		checkLazyField(entity, em, testArray);
+
+		/**
+		 * Set a non lazy field, therefore the lazyData field will be LazyPropertyInitializer.UNFETCHED_PROPERTY
+		 * for both state and newState so the field should not change. This should no longer cause a ClassCastException.
+		 */
+	  	em.getTransaction().begin();
+		entity = em.find(EntityWithLazyProperty.class, entity.getId());
+		entity.setSomeField("TEST1");
+		em.getTransaction().commit();
+		checkLazyField(entity, em, testArray);
+
+		/**
+		 * Set the updateLazyFieldInPreUpdate flag so that the lazy field is updated from within the
+		 * PreUpdate annotated callback method. So state == LazyPropertyInitializer.UNFETCHED_PROPERTY and
+		 * newState == EntityWithLazyProperty.PRE_UPDATE_VALUE. This should no longer cause a ClassCastException.
+		 */
+		em.getTransaction().begin();
+		entity = em.find(EntityWithLazyProperty.class, entity.getId());
+		entity.setUpdateLazyFieldInPreUpdate(true);
+		entity.setSomeField("TEST2");
+		em.getTransaction().commit();
+		checkLazyField(entity, em, EntityWithLazyProperty.PRE_UPDATE_VALUE);
+
+		/**
+		 * Set the updateLazyFieldInPreUpdate flag so that the lazy field is updated from within the
+		 * PreUpdate annotated callback method and also set the lazyData field directly to testArray1. When we reload we
+		 * should get EntityWithLazyProperty.PRE_UPDATE_VALUE.
+		 */
+		em.getTransaction().begin();
+		entity = em.find(EntityWithLazyProperty.class, entity.getId());
+		entity.setUpdateLazyFieldInPreUpdate(true);
+		entity.setLazyData(testArray);
+		entity.setSomeField("TEST3");
+		em.getTransaction().commit();
+		checkLazyField(entity, em, EntityWithLazyProperty.PRE_UPDATE_VALUE);
+
+		em.close();
+	}
+
+	private void checkLazyField(EntityWithLazyProperty entity, EntityManager em, byte[] expected) {
+		// reload the entity and check the lazy value matches what we expect.
+		em.getTransaction().begin();
+		entity = em.find(EntityWithLazyProperty.class, entity.getId());
+		assertEquals(expected, entity.getLazyData());
+		em.getTransaction().commit();
+	}
 }

hibernate-entitymanager/src/test/java/org/hibernate/jpa/test/callbacks/EntityWithLazyProperty.java

@@ -0,0 +1,63 @@
+package org.hibernate.jpa.test.callbacks;
+
+import javax.persistence.*;
+
+/**
+ * Test entity with a lazy property which requires build time instrumentation.
+ */
+@Entity
+public class EntityWithLazyProperty {
+
+    public static final byte[] PRE_UPDATE_VALUE = new byte[]{0x2A, 0x2A, 0x2A, 0x2A};
+
+    @Id
+    @GeneratedValue
+    private Long id;
+
+    @Basic(fetch = FetchType.LAZY)
+    private byte[] lazyData;
+
+    private String someField;
+
+    private boolean updateLazyFieldInPreUpdate;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(final Long id) {
+        this.id = id;
+    }
+
+    public byte[] getLazyData() {
+        return lazyData;
+    }
+
+    public void setLazyData(final byte[] lazyData) {
+        this.lazyData = lazyData;
+    }
+
+    public String getSomeField() {
+        return someField;
+    }
+
+    public void setSomeField(String someField) {
+        this.someField = someField;
+    }
+
+    public boolean isUpdateLazyFieldInPreUpdate() {
+        return updateLazyFieldInPreUpdate;
+    }
+
+    public void setUpdateLazyFieldInPreUpdate(boolean updateLazyFieldInPreUpdate) {
+        this.updateLazyFieldInPreUpdate = updateLazyFieldInPreUpdate;
+    }
+
+    @PreUpdate
+    public void onPreUpdate() {
+        //Allow the update of the lazy field from within the pre update to check that this does not break things.
+        if(isUpdateLazyFieldInPreUpdate()) {
+            this.setLazyData(PRE_UPDATE_VALUE);
+        }
+    }
+}