Hibernate version:
3.2 GA and annotation 3.2 GA

Mapping documents:
@Entity
public class Entity {
// Has a DB generated id

@OneToMany (mappedBy = "entity", cascade = CascadeType.ALL)
private List<Thing> things;

// Getters and setters
}

@Entity
public class Thing {
// Has a DB generated id

@OneToOne(optional = false)
@JoinColumn(name = "entity_id", nullable = false)
private Entity entity;

// Getters and setters
}

Code between sessionFactory.openSession() and session.close():
/* there are entities and things in the database already. Entity 1 has 3 things. */
Entity entity = session.load(Entity.class, 1);

Thing thing = new Thing();
thing.setEntity(entity);

entity.getThings().add(thing);

session.update(entity);
session.flush();

Name and version of the database you are using:
MySql 5.0 - InnoDB tables

The generated SQL (show_sql=true):
Two insert statements are generated.

Using this code (well, this is a trimmed down version) saves the newly created object twice (total of 5 objects for entity 1). This was verified by looking at the DB afterwards. However if you reference an item in the things collection before the update, or call .size on the collection, it is only saved once.

Is this a bug in the hibernate proxying, or am I doing something wrong?

I came across this problem yesterday whilst testing some code. I've found that changing the cascade type to MERGE resolves the issue but cannot understand why it is happening in the first place. The other interesting thing is that if I run the code in debug mode with a cascade type of ALL the problem doesn't occur.

Can you tell me if you have found any reasons why this problem occurs.

Thanks

Stu.