Hi,
----- Original Message -----
From: "Martin Kalén" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Friday, December 05, 2003 7:14 AM
Subject: Re: hot to reload cached object?
> Hi!
>
> Yes; removeFromCache will remove the weak reference to the object and
> make it eligble for garbage collection.
>
> Jair da Silva Ferreira Júnior wrote:
>
> > transaction.begin();
> > Customer c=new Customer();
> > c.setName("customer");
> > transaction.lock(c,transaction.WRITE); //persist the new
customer
> > transaction.commit();
> >
> > //after some time someone changes Customer's name to "new
customer"
> > directly in the database
> > transaction.begin();
> > Customer c=loadCustomer(); // loads the customer persisted
before
> > from cache
> > Order o=new Order();
> > o.setCustomer(c);
> > cache.reloadObject(c); //reload object data from database
> > boolean referenceOk=(c==o.getCustomer()); // I wanted
referenceOk to
> > be true
>
> To me, it looks like you could just flip the order of setting the
> Customer reference in Order and do:
>
> Customer c=loadCustomer(); // loads the customer persisted before
> cache.reloadObject(c); // reload object data from database
> Order o=new Order();
> o.setCustomer(c);
I know that fliping the order of setting the Customer reference in Order
would solve the problem. But that is not my objective. I'm sorry I could not
explain you correctly what I wanted. This code better captures my intention:
transaction.begin();
Customer c=new Customer();
c.setName("customer");
Order o=new Order();
o.setCustomer(c);
transaction.lock(c,transaction.WRITE); //persist the new customer
transaction.lock(o,transaction.WRITE); //persist the new order
transaction.commit();
//after some time someone changes Customer's name to "new customer"
directly in the database
transaction.begin();
Customer c=loadCustomer(); // runs a query to load the Customer
persisted before from cache
Order o=loadOrder(); // runs a query to load the Order persisted
before from cache
cache.reloadObject(c); //reload object data from database mutating
the input parameter "c"
boolean referenceOk=(c==o.getCustomer()); // I wanted referenceOk to
be true
boolean dataReloaded="new customer".equals(c.getName()); //I wanted
dataReloaded to be true
transaction.commit();
>
> I cant't tell from your example wether cache.reloadObject(c) returns a
> new pointer or mutates the input parameter. If it is not mutating you
> could pick up the newly loaded object reference as return value and do:
>
> Customer c=loadCustomer();
> c = cache.reloadObject(c);
> Order o=new Order();
> o.setCustomer(c);
cache.reloadObject(c) should mutate the input parameter instead of
returning a new pointer
> Also, have a look at the "auto-retrieve" and "refresh" attributes in the
> repository file to tweak how a Customer-reference from an Order should
> be updated when re-loading the whole Order.
What do you mean by "re-loading the whole Order"? Do you mean re-loading
it from cache or from the database? If auto-retrieve="true" and
refresh="true", when the Customer is removed from cache (using
broker.removeFromCache(c)), would the Order reference to the customer be
automaticaly updated too? If true, when would this automaticaly update
happen? After a query to Customer (reloading it from the database) or after
a query to Order (getting it from the cache)?
> In one of our applications we have wrapped load-operations to be:
> 1. remove from cache
> 2. get object by query
>
> Any reference- or collection-descriptors in step 2 have @refresh="true"
> in the repository and will be reloaded as well (provided that you follow
> reference-descriptors and remove them from cache too in step 1). Or you
> could just follow Armin Waibel's instructions about clearing the whole
> cache if you would like _all_ objects to be reloaded.
I've read the documentation of the refresh atribute in the
<class-descriptor> tag but I'm still confused. If refresh="true" when an
object is loaded from cache, are its data and references also reloaded from
the database? If this is true, what is the point of retrieving it from
cache?
Thank you very much for your help.
Sincerely,
Jair Jr
> --
> Martin Kalén
> Curalia AB Web: http://www.curalia.se
> Orrspelsvägen 2B Mail: [EMAIL PROTECTED]
> SE-182 79 Stocksund Tel: +46-8-410 064 40
>
>
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