Hi,
ABOU LINA wrote:
Thanks Armin, your reply is very helpfull.
so there is no direct solution we must call store two time , one for A
another for B.
in your opinion why is not possible to use the same philosophy of the
invers-foreignekey wich is used in 1:n ????
Assume you are using database identity based PK's. In that case the PK
value was assigned after the object was insert, e.g. A. Then OJB was
able to assign the FK in B and insert B. But the FK to B in A wasn't
set, thus OJB have to assign the FK in A and update A.
If you manage the PK values by your own and the PK values are valid
before insert of objects, it's possible to establish the bidirectional
objects with a single store call.
an other question about performance this time :
i don't know how can we do it in OJB ; when OJB prepare a statement (for
read) by default he make SELECT * FROM ... so i think if we have
a posibility to specify only fields that's we need instead of (*) we got a
good result at performance level in reading. ??? how can i do this in OJB
If only need a few fields of an persistent object class and not the
whole persistent object itself, it's recommended to use ReportQueries:
http://db.apache.org/ojb/docu/guides/query.html#Report+Queries
Much more complex will be the use of different metadata profiles
(different persistent object metadata mapping for the same objects),
e.g. a normal profile and specific read profiles (without specific fields).
http://db.apache.org/ojb/docu/guides/metadata.html#Per+thread+metadata+changes
regards,
Armin
thx in advance.
On 2/14/06, Armin Waibel <[EMAIL PROTECTED]> wrote:
Hi,
ABOU LINA wrote:
Hi,
i give you this sample example :
in case A<---->B [1:n] :
the mapping of this bidiractional navigation is guaranted by the
use of
inverse-foreignkey :
Mapping A classe :
----------------------------------------------------
<collection-descriptor
name="allB"
element-class-ref="B"
>
<inverse-foreignkey field-ref="aId"/>
</collection-descriptor>
Mapping B class :
------------------------------
<reference-descriptor
name="a"
class-ref="A"
>
<foreignkey field-ref="aId"/>
</reference-descriptor>
so in case of A<---->B [1:1] i need a bidirectional navigation !!!!!
how to use ????
Do you mean how to map it?
Declare in both classes A and B a 1:1 reference-descriptor (both class
tables need a FK column).
How to insert?
This depends strongly on the used auto-xxx settings. If
auto-update/delete is enabled (and PK values handled by OJB) you can do
e.g.:
broker.beginTransaction();
// first store both objects
broker.store(a, ObjectModification.INSERT);
// or let OJB detect the needed operation (more overhead)
//broker.store(a);
broker.store(b, ObjectModification.INSERT);
// now set references
a.setRelatedB(b);
b.setRelatedA(a);
// update both
broker.store(a, ObjectModification.UPDATE);
broker.commitTransaction();
or ()
// set references first
a.setRelatedB(b);
b.setRelatedA(a);
broker.beginTransaction();
// store both objects
broker.store(a);
// update b to force OJB to set the FK
// back to a (was 'null' after first store call)
broker.store(b);
broker.commitTransaction();
or if auto-update 'link' is used
broker.beginTransaction();
// first store both objects
broker.store(a, ObjectModification.INSERT);
broker.store(b, ObjectModification.INSERT);
// now set references
a.setRelatedB(b);
b.setRelatedA(a);
// update both
broker.store(a, ObjectModification.UPDATE);
broker.store(b, ObjectModification.UPDATE);
broker.commitTransaction();
...
regards,
Armin
my config :
1. ojb 1.0.3
2. i use the broker (PB-API)
Thanks a lot ....
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