Package org.hibernate.engine.internal

Class ManagedTypeHelper

java.lang.Object

org.hibernate.engine.internal.ManagedTypeHelper

public final class ManagedTypeHelper
extends Object

This is a helper to encapsulate an optimal strategy to execute type checks for interfaces which attempts to avoid the performance issues tracked as JDK-8180450; the problem is complex and explained better on the OpenJDK tracker; we'll focus on a possible solution here.

To avoid polluting the secondary super-type cache, the important aspect is to not switch types repeatedly for the same concrete object; using a Java agent which was developed for this purpose (https://github.com/franz1981/type-pollution-agent) we identified a strong case with Hibernate ORM is triggered when the entities are using bytecode enhancement, as they are being frequently checked for compatibility with the following interfaces:

• PersistentAttributeInterceptable
• ManagedEntity
• SelfDirtinessTracker
• Managed
• HibernateProxy

Some additional interfaces are involved in bytecode enhancement (such as ManagedMappedSuperclass), but some might not be managed here as there was no evidence of them triggering the problem; this might change after further testing.

The approach we pursue is to have all these internal interfaces extend a single interface PrimeAmongSecondarySupertypes which then exposes a type widening contract; this allows to consistently cast to PrimeAmongSecondarySupertypes exclusively and avoid any further type checks; since the cast consistently happens on this interface we avoid polluting the secondary super type cache described in JDK-8180450.

This presents two known drawbacks:

1# we do assume such user entities aren't being used via interfaces in hot user code; this is typically not the case based on our experience of Hibernate usage, but it can't be ruled out.

2# we're introducing virtual dispatch calls which are likely going to be megamorphic; this is not great but we assume it's far better to avoid the scalability issue.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	ManagedTypeHelper.ManagedEntityConsumer
static interface	ManagedTypeHelper.PersistentAttributeInterceptableAction<T>	This interface has been introduced to mitigate JDK-8180450. Sadly, using BiConsumer will trigger a type pollution issue because of generics type-erasure: BiConsumer's actual parameters types on the lambda implemention's BiConsumer.accept(T, U) are stealthy enforced via checkcast, messing up with type check cached data.
static interface	ManagedTypeHelper.SelfDirtinessTrackerAction<T>
static interface	ManagedTypeHelper.SelfDirtinessTrackerConsumer

Constructor Summary

Constructors

Constructor	Description
ManagedTypeHelper()

Method Summary

Modifier and Type	Method	Description
static CompositeOwner	asCompositeOwner(Object entity)	Cast the object to CompositeOwner (using this is highly preferrable over a direct cast)
static CompositeTracker	asCompositeTracker(Object entity)	Cast the object to CompositeTracker (using this is highly preferrable over a direct cast)
static HibernateProxy	asHibernateProxy(Object entity)	Cast the object to HibernateProxy (using this is highly preferrable over a direct cast)
static HibernateProxy	asHibernateProxyOrNull(Object entity)	Cast the object to an HibernateProxy, or return null in case it is not an instance of HibernateProxy
static ManagedEntity	asManagedEntity(Object entity)	Cast the object to ManagedEntity (using this is highly preferrable over a direct cast)
static PersistentAttributeInterceptable	asPersistentAttributeInterceptable(Object entity)	Cast the object to PersistentAttributeInterceptable (using this is highly preferrable over a direct cast)
static PersistentAttributeInterceptable	asPersistentAttributeInterceptableOrNull(Object entity)
static SelfDirtinessTracker	asSelfDirtinessTracker(Object entity)	Cast the object to SelfDirtinessTracker (using this is highly preferrable over a direct cast)
static boolean	isCompositeOwner(Object entity)
static boolean	isCompositeTracker(@Nullable Object entity)
static boolean	isHibernateProxy(Object entity)
static boolean	isManagedEntity(Object entity)
static boolean	isManagedType(Class type)
static boolean	isPersistentAttributeInterceptable(Object entity)
static boolean	isPersistentAttributeInterceptableType(Class type)
static boolean	isSelfDirtinessTracker(Object entity)
static boolean	isSelfDirtinessTrackerType(Class type)
static void	processIfManagedEntity(Object entity, ManagedTypeHelper.ManagedEntityConsumer action)
static <T> void	processIfPersistentAttributeInterceptable(Object entity, ManagedTypeHelper.PersistentAttributeInterceptableAction<T> action, T optionalParam)	Helper to execute an action on an entity, but exclusively if it's implementing the interface.
static <T> void	processIfSelfDirtinessTracker(Object entity, ManagedTypeHelper.SelfDirtinessTrackerAction<T> action, T optionalParam)	If the entity is implementing SelfDirtinessTracker, apply some action to it; this action should take a parameter of type T.
static void	processIfSelfDirtinessTracker(Object entity, ManagedTypeHelper.SelfDirtinessTrackerConsumer action)	If the entity is implementing SelfDirtinessTracker, apply some action to it.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ManagedTypeHelper

public ManagedTypeHelper()

Method Details

isManagedType

public static boolean isManagedType(Class type)

Parameters:

type -

Returns:

true if and only if the type is assignable to a type.

isSelfDirtinessTrackerType

public static boolean isSelfDirtinessTrackerType(Class type)

Parameters:

type -

Returns:

true if and only if the type is assignable to a type.

isPersistentAttributeInterceptableType

public static boolean isPersistentAttributeInterceptableType(Class type)

Parameters:

type -

Returns:

true if and only if the type is assignable to a type.

isManagedEntity

public static boolean isManagedEntity(Object entity)

Returns:

true if and only if the entity implements ManagedEntity

isHibernateProxy

public static boolean isHibernateProxy(Object entity)

Returns:

true if and only if the entity implements HibernateProxy

isPersistentAttributeInterceptable

public static boolean isPersistentAttributeInterceptable(Object entity)

Parameters:

entity -

Returns:

true if and only if the entity implements

isSelfDirtinessTracker

public static boolean isSelfDirtinessTracker(Object entity)

Parameters:

entity -

Returns:

true if and only if the entity implements

isCompositeOwner

public static boolean isCompositeOwner(Object entity)

Parameters:

entity -

Returns:

true if and only if the entity implements

isCompositeTracker

public static boolean isCompositeTracker(@Nullable Object entity)

Parameters:

entity -

Returns:

true if and only if the entity implements

processIfPersistentAttributeInterceptable

public static <T> void processIfPersistentAttributeInterceptable(Object entity,
 ManagedTypeHelper.PersistentAttributeInterceptableAction<T> action,
 T optionalParam)

Helper to execute an action on an entity, but exclusively if it's implementing the interface. Otherwise no action is performed.

Type Parameters:

T - the type of the additional parameter.

Parameters:

entity -

action - The action to be performed; it should take the entity as first parameter, and an additional parameter T as second parameter.

optionalParam - a parameter which can be passed to the action

processIfSelfDirtinessTracker

public static void processIfSelfDirtinessTracker(Object entity,
 ManagedTypeHelper.SelfDirtinessTrackerConsumer action)

If the entity is implementing SelfDirtinessTracker, apply some action to it. It is first cast to SelfDirtinessTracker using an optimal strategy. If the entity does not implement SelfDirtinessTracker, no operation is performed.

Parameters:

entity -

action -

processIfManagedEntity

public static void processIfManagedEntity(Object entity,
 ManagedTypeHelper.ManagedEntityConsumer action)

processIfSelfDirtinessTracker

public static <T> void processIfSelfDirtinessTracker(Object entity,
 ManagedTypeHelper.SelfDirtinessTrackerAction<T> action,
 T optionalParam)

If the entity is implementing SelfDirtinessTracker, apply some action to it; this action should take a parameter of type T. It is first cast to SelfDirtinessTracker using an optimal strategy. If the entity does not implement SelfDirtinessTracker, no operation is performed.

Type Parameters:

T - the type of the additional parameter.

Parameters:

entity -

action -

optionalParam - a parameter which can be passed to the action

asPersistentAttributeInterceptable

public static PersistentAttributeInterceptable asPersistentAttributeInterceptable(Object entity)

Cast the object to PersistentAttributeInterceptable (using this is highly preferrable over a direct cast)

Parameters:

entity - the entity to cast

Returns:

the same instance after casting

Throws:

ClassCastException - if it's not of the right type

asPersistentAttributeInterceptableOrNull

public static PersistentAttributeInterceptable asPersistentAttributeInterceptableOrNull(Object entity)

asHibernateProxy

public static HibernateProxy asHibernateProxy(Object entity)

Cast the object to HibernateProxy (using this is highly preferrable over a direct cast)

Parameters:

entity - the entity to cast

Returns:

the same instance after casting

Throws:

ClassCastException - if it's not of the right type

asManagedEntity

public static ManagedEntity asManagedEntity(Object entity)

Cast the object to ManagedEntity (using this is highly preferrable over a direct cast)

Parameters:

entity - the entity to cast

Returns:

the same instance after casting

Throws:

ClassCastException - if it's not of the right type

asCompositeTracker

public static CompositeTracker asCompositeTracker(Object entity)

Cast the object to CompositeTracker (using this is highly preferrable over a direct cast)

Parameters:

entity - the entity to cast

Returns:

the same instance after casting

Throws:

ClassCastException - if it's not of the right type

asCompositeOwner

public static CompositeOwner asCompositeOwner(Object entity)

Cast the object to CompositeOwner (using this is highly preferrable over a direct cast)

Parameters:

entity - the entity to cast

Returns:

the same instance after casting

Throws:

ClassCastException - if it's not of the right type

asSelfDirtinessTracker

public static SelfDirtinessTracker asSelfDirtinessTracker(Object entity)

Cast the object to SelfDirtinessTracker (using this is highly preferrable over a direct cast)

Parameters:

entity - the entity to cast

Returns:

the same instance after casting

Throws:

ClassCastException - if it's not of the right type

asHibernateProxyOrNull

public static HibernateProxy asHibernateProxyOrNull(Object entity)

Cast the object to an HibernateProxy, or return null in case it is not an instance of HibernateProxy

Parameters:

entity - the entity to cast

Returns:

the same instance after casting or null if it is not an instance of HibernateProxy