[Hibernate-JIRA] Created: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
9:22 a.m.
lazy fetching ManyToOne produces inproper proxies when using single table inheritance
strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Type: Bug
Components: core
Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation to
"c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy object
remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
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11:42 a.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
S.Schnabl commented on HHH-2477:
--------------------------------
Same misbehavoir in this configuration (single table inheritance strategy and lazy
*toOne) for HibernateProxyHelper:
HibernateProxyHelper.getClassWithoutInitializingProxy(car_proxy) only returns
vehicle.class. Should be car.class
Please fix it !
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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9:36 a.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
S.Schnabl commented on HHH-2477:
--------------------------------
The HIA Book states the following for lazy *toOne associations:
"...Hibernate would proxy the lazy association. In this case, we wouldn't be able
to perform a typecast to the concrete class CreditCard at runtime, and even the instanceof
operator would behave strangely....".
This means, you cannot lazy load a *toOne association and expect, that hibernate knows the
real concrete class of your proxy object without hitting the database once. Without a
database hit hibernate simply cannot determine the concrete class. To get the concrete
class, YOU simply have to know the class and must reload the association from the
database, ex. :
Car car = (Car) session.load( Car.class, user.getVehicle.getId() );
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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5:31 a.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Adam T commented on HHH-2477:
-----------------------------
See "Section 19.1.3. Single-ended association proxies" of the Hibernate
Reference Guide.
http://www.hibernate.org/hib_docs/reference/en/html/performance.html
This is a known limitation when using proxies. It is due to Java's single-inheritance
model. To work around the limitation and still use lazy loading, create interfaces for
your entity classes and program to those interfaces.
public interface Vehicle {}
public interface Car extends Vehicle {}
public class VehicleBean implements Vehicle {}
public class CarBean implements Car {}
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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1:08 p.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
S.Schnabl commented on HHH-2477:
--------------------------------
Thx for the tip !
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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1:05 p.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Sebastian Kirsch commented on HHH-2477:
---------------------------------------
Just to widen the problem: I am facing the same problem with JOINED inheritance.
Can anybody change the issue's title/topic?
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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9:27 a.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Tun Schlechter commented on HHH-2477:
-------------------------------------
This is a very annoying BUG and unfortunately, the above descriptions and motivations
suggest that it will not be easy to fix it. If you are not too much annoyed by the
limitations of Toplink-essentials, you might try it as a persistence provider, it does not
have this bug.
Otherwise, you can add a persistent attribute to your classes that takes the classname
upon construction. Later you will evaluate this attribute, instead of using the instanceof
operator. With JOINED Inheritance, the solution has the added benefit, that you can
determine the classname manually in your DB while looking at the table of the highest
superclass.
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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11:57 a.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Tun Schlechter commented on HHH-2477:
-------------------------------------
Unfortunately, this hack only enables you to know the real classname, you still cannot
cast the object...
Finding the exact class works as well with the dynamic class.isInstance(object) - Test,
even if instanceof operator test fails...
From this, one might expect that "dynamic"
class.cast(object) casting works even if (class) object casting does not, but
unfortunately, it does not.
Maybe working around toplink limitations is easier, we will see...
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
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6:22 p.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Chris Lowe commented on HHH-2477:
---------------------------------
The workaround is particularly nasty when in an EJB3 environment where we are faced with
using a non-standard Hibernate annotations and use of alternate proxies.
Can anyone from the Hibernate team comment on if/when this issue will be fixed?
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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7:17 p.m.
New subject: [Hibernate-JIRA] Closed: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Chris Bredesen closed HHH-2477.
-------------------------------
Resolution: Rejected
S. Schnabl correctly quotes HIA and Adam T. correctly quotes the manual. This is
unfixable because at the time the proxy is generated, Hibernate has no knowledge of what
the concrete implementation might be. Once the proxy is hydrated however, the
implementation will be the correct concrete class and as such the instances *behavior*
will be correct.
If you must have castable/instanceof then you'll need to load() from Session and pass
the concrete class so that the resulting instance is what you expect. Note that a
database hit will not occur since the instance is already in Session.
You can also use the Visitor pattern as described here:
http://www.hibernate.org/280.html
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
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9:16 p.m.
New subject: [Hibernate-JIRA] Commented: (HHH-2477) lazy fetching ManyToOne produces inproper proxies when using single table inheritance strategy
[
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477?page=c...
]
Chris Lowe commented on HHH-2477:
---------------------------------
Chris, thanks for the prompt response.
I accept your workarounds are valid for a pure Hibernate environments, but as a pure EJB3
environment this isn't this still an issue?
Like Sebastian Kirsch comments above, I'm getting this issue with a JOINED
inheritance. Before adding a lazy association my EJBQL was returning a subclass as
expected. After adding the lazy association I now get the root superclass. This
behaviour was not expected. I've even gone as far specifying my query in terms of the
expected subclass, but I still get the root superclass - so how can I even get to my
subclass at all?! What's more, the lazy associations that I have specified are not
even directly against any of the classes in the inheritance structure - they're on the
One side of a ManyToOne. The Many side is on the entities in the inheritance structure,
but aren't the Hibernate implementations of the various collections supposed to
prevent the need for proxying the parent class?
So with respect to Hibernate being the provider to an EJB3 implementation, is this still
an issue? Or is this something that needs to be taken up elsewhere?
I feel like I'm faced with something that essentially makes essentially makes entity
Inheritance and FetchStrategy.LAZY mutually exclusive and that just seems wrong. There
was nothing to hint at this problem in the Hibernate EJB3 docs (or even after scanning
through the EJB3 spec for that matter).
Best regards,
Chris.
lazy fetching ManyToOne produces inproper proxies when using single
table inheritance strategy
----------------------------------------------------------------------------------------------
Key: HHH-2477
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2477
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.1
Environment: hibernate 3.2.1-GA, postgresql 8.1
Reporter: Daniel Nguyen
Attachments: bug.zip
Original Estimate: 1 hour
Remaining Estimate: 1 hour
I have entity base class Vehicle and entity class Car which extends Vehicle (using single
table inheritance strategy).
I also have entity class User which have single-ended @ManyToOne relation from User to
Vehicle with lazy fetching.
Now there is a Car instance "c" and User instance "u" with relation
to "c". Lazily fetching vehicle from "u" results with proxy object
"o" which is instanceof Vehicle but not instanceof Car as expected. So it's
impossible cast "o" to Car or at least read any of Car's property from
"o".
This is serious problem when inheritance is extensively used because inproper proxy
object remains in cache. To walkaround I'd have to resign with lazy fetching (much
performance loss) or manually replace proxy object in cache.
testing code:
SessionFactory sf = null;
Session s = null;
Transaction tx = null;
try
{
sf = cfg.buildSessionFactory();
s = sf.openSession();
tx = s.beginTransaction();
//create car
Car car = new Car();
car.setIdVehicle(1);
car.setAge(5);
s.save(car);
//create user of car
User user = new User();
user.setIdUser(1);
user.setVehicle(car);
s.save(user);
//make sure it is actually added
s.flush();
// test 1 - works ok, because we loaded vehicle before user
s.clear(); //clear cache
Vehicle vv = (Vehicle)s.get(Vehicle.class, 1);
User uu = (User)s.get(User.class, 1);
//we know that user vehicle is actually a Car
Car cc = (Car)uu.getVehicle();
// test 2 - fails, when using lazy fetching
s.clear(); //clear cache
User u = (User)s.get(User.class, 1);
Vehicle v = u.getVehicle();
//we know that user vehicle is actually a Car
//so we cast to Car but ClassCastException is raised!!!
Car c = (Car)v;
//let's check what's actual class of v
System.out.println(v.getClass().getName());
System.out.println(v.getClass().getSuperclass().getName());
//result:
// test.hibernate.Vehicle$$EnhancerByCGLIB$$12ce1883
// test.hibernate.Vehicle
//but I expected:
// test.hibernate.Car$$EnhancerByCGLIB$$xxxxx
// test.hibernate.Car
}
finally
{
if (tx!=null)
tx.rollback();
if (s!=null)
s.close();
if (sf!=null)
sf.close();
}
--
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5771
days inactive
6309
days old
hibernate-issues@lists.jboss.org
10 comments
7 participants
participants (7)
-
Adam T (JIRA) -
Chris Bredesen (JIRA)
-
Chris Lowe (JIRA)
-
Daniel Nguyen (JIRA)
-
S.Schnabl (JIRA)
-
Sebastian Kirsch (JIRA)
-
Tun Schlechter (JIRA)