add code example to javadoc of CustomEntityDirtinessStrategy

Author: gavinking

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

@@ -15,6 +15,40 @@
  * since, by default, Hibernate must check each of the entity's attribute values one by one. Sometimes, an
  * application already has knowledge of an entity's dirtiness and making use of that information would save some
  * work. This contract allows the application to take over the task of determining if an entity is dirty.
+ * <p>
+ * For example, the application program might define an interface implemented by entities which keep track of
+ * their own modified fields:
+ * <pre>
+ * public interface DirtyTracker {
+ *     Set&lt;String&gt; changes();
+ * }
+ * </pre>
+ * Then the following implementation of {@code CustomEntityDirtinessStrategy} would be used:
+ * <pre>
+ * public class DirtyTrackerDirtinessStrategy implements CustomEntityDirtinessStrategy {
+ *     &#64;Override
+ *     public boolean canDirtyCheck(Object entity, EntityPersister persister, Session session) {
+ *         return entity instanceof DirtyTracker;
+ *     }
+ *
+ *     &#64;Override
+ *     public boolean isDirty(Object entity, EntityPersister persister, Session session) {
+ *         return !((DirtyTracker) entity).changes().isEmpty();
+ *     }
+ *
+ *     &#64;Override
+ *     public void resetDirty(Object entity, EntityPersister persister, Session session) {
+ *         ((DirtyTracker) entity).changes().clear();
+ *     }
+ *
+ *     &#64;Override
+ *     public void findDirty(Object entity, EntityPersister persister, Session session, DirtyCheckContext dirtyCheckContext) {
+ *         dirtyCheckContext.doDirtyChecking( attributeInformation ->
+ *                ((DirtyTracker) entity).changes().contains( attributeInformation.getName() ) );
+ *     }
+ * }
+ * </pre>
+ *
  *
  * @see org.hibernate.cfg.AvailableSettings#CUSTOM_ENTITY_DIRTINESS_STRATEGY
  * @see org.hibernate.cfg.Configuration#setCustomEntityDirtinessStrategy(CustomEntityDirtinessStrategy)

hibernate-core/src/main/java/org/hibernate/cfg/Configuration.java

@@ -164,7 +164,7 @@ public class Configuration {
 
 	private Map<String, SqmFunctionDescriptor> customFunctionDescriptors;
 	private List<AuxiliaryDatabaseObject> auxiliaryDatabaseObjectList;
-	private HashMap<Class<?>, ConverterDescriptor<?,?>> attributeConverterDescriptorsByClass;
+	private Map<Class<?>, ConverterDescriptor<?,?>> attributeConverterDescriptorsByClass;
 	private List<EntityNameResolver> entityNameResolvers = new ArrayList<>();
 
 	// used to build SF