Hi,
@Matt:
thanks for your elaborate answer. My setup is a lot like yours: Spring
manages the business objects and the DAOs. My problem is this:
Struts->Business layer->HibernateDAO->Database will return a hibernate
proxy of my dom object. I have to load all objects lazily, because our
db has got a very hierarchical layout. This in turn means, that I cannot
use Hibernate.initialize on all collections, because it would be to
expensive. Thus, I return an object, which is partially loaded - if my
action accesses an attribute, which has not been initialized, I'll have
to deal with a LazyInitializationExceptions, which, IMO, is bad.
Apart from that, I'd like to ask, how you deal with lazy loading in
general. Do you always return "complete", that is fully initialized
objects? If not, how do you reflect this in your business layer? Will
there be multiple methods for each object, depending on the number of
collections that need to be initialized?
@Marco
again, thank you for your reply. My problem with DTOs is, that I expect
to have about 150 dom objects, which would result in 150 DTOs. These are
objects that I actually do not need - it'll just decrease performance.
But unfortunately I do see an alternative to DTOs so far, so in case
nobody else comes up with a brilliant idea, I guess I'll have to
implement it that way.
BTW: Is it possible to use BeanUtils to copy entire beans or will I have
to use copy() on each property? Are DynaBeans (beanUtils) an alternative?
Thanks,
Tom
Matt Morton wrote:
Hi Tom
In our app we are using pattern where Struts calls a method from what I call
a service layer object. Then the service layer calls the dao interface.
Then there is an implementation of the dao for Hibernate. So the call stack
is something like:
Struts Action -> ServiceManager.getSomeObject(Integer id) -> DAO.get(Integer
id) -> return Object
The service layer are actually Spring beans. These beans are bound to the
dao's in the Spring appContext. I am also using Spring to manage the Struts
actions.
I have always wrestled with the DTO question. I guess I haven't seen the
need for it while using Spring and Hibernate. I have also created objects
that are specific to the view object (like a set of menu links) that is
being created dynamically and then populated that with the domain objects
values that were needed. This latter solution is more like a poor mans (in
regards too time) JSF.
With regards to the LazyLoading issues for collections that reference other
domain objects I usually use the Hibernate.initialize(Object) method. It
will then go through and load the objects in the collection that are
necessary for what domain object you are using. Then send the object back
to the action to be manipulated as necessary.
Probably not perfect but seems to provide the flexibility we need. I am
interested to know what others are doing too.
Hope that helps.
Matt Morton
On 11/30/05, Tom Ziemer <[EMAIL PROTECTED]> wrote:
Hi,
I have got a little problem with Hibernate - well actually it is only
partially related to it:
My app uses Spring + Hibernate (lazy loading), but should I return the
value beans (dom) from Hibernate to my Struts actions? If I do this, I'd
have to deal with LazyInitializationExceptions for collections that have
been lazy-loaded. In my opinion, this would be a horrible design because
the view would have to know about the data access tier. On the other
hand, I've read, that "DTOs are evil" - but how can I solve this problem
without DTOs?
I am sure, lots of you are using
Hibernate/{YOUR_LIST_OF_OTHER_GREAT_FRAMEWORKS_HERE}/Struts and I'd be
grateful for any help.
Thanks,
Tom
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