In your first example, you'll end up adding a new row to the B table
each time you do the new assignment -- you'll see an INSERT statement
each time the code executes.
In the second, you'll end up updating a single row in the B table each
time -- you'll see an UPDATE statement.
You could also set up the relation such that your first example would
result in a DELETE for the old row and an INSERT for the new row. You
would do this with the @Dependent annotation.
-Patrick
On Nov 6, 2007 7:34 PM, Gul Onural <[EMAIL PROTECTED]> wrote:
>
> Let say I have classB inside classA, both are @Entity and @OneToOne
> relationships between the two.
>
> Let say I already persisted classA and classB and I want to update
> variable b of the ClassA using following code.
>
> I am trying to understand if the database effect of assigning a "new"
> ClassB to variable b (Code piece-I below) is any different than
> getting b first than updating B's member variables (Code piece -II) ?
>
> // Pseudo code piece - I
> startTransaction
> X = findClassA
> X.setb(new ClassB)
> commitTransaction
>
> // Pseudo code piece - II
> startTransaction
> X = findClassA
> X.getb.setName("...)
> commitTransaction
>
> public class ClassA {
> int idA;
> @OneToMany(mappedBy = "myA", cascade = CascadeType.ALL,
> targetEntity = classB, fetch = FetchType.EAGER)
> ClassB b;
> String name;
> ...
> }
>
> public class ClassB {
> int idB
> @OneToOne
> @JoinColumn(name = "idA")
> private ClassA myA;
> ....
> }
>
>
>
--
Patrick Linskey
202 669 5907
