Hi Tom, This is actually a common problem and a pattern called Open Session in View was used to solve that specific problem. Because you are also using Spring with Hibernate, you can check out: http://www.springframework.org/docs/api/org/springframework/orm/hibernate/support/OpenSessionInViewFilter.html What I did was just add this to my web.xml: <filter> <filter-name>hibernateFilter</filter-name> <filter-class> org.springframework.orm.hibernate3.support.OpenSessionInViewFilter </filter-class> </filter> I use to also get the lazy initialization exception but this filter will allow lazy loading in the web view. I dont think you should be checking for that exception in you dao if you implement the open session in view pattern. Jadeler
Tom Ziemer <[EMAIL PROTECTED]> wrote: Hi Marco, I guess, I'll go with the DTO approach if I'll get no further input. Will BeanUtils.copyProperties also work on nested collections, though? When you encounter a LazyInitializationException, it means that you access a collection of an object that is no longer connected to a HibernateSession. One option would be to reconnect the object to a new session. If such an exception is thrown, I guess this should be handled by the DAO, so that the business layer does not need to know that hibernate is used for data access. I'll look at the BeanUtils now... Thanks again, Tom Marco Mistroni wrote: > Hello, > You invoke BeanUtils.copyProperties on two objects, it will copy > Only properties that are the same between two objects.. > As I said, could you handle your lazyexception by simply building another > collection out of the collection returned by hibernate? > > Btw, sorry for my ignorance about that lazy exception, but what are you > Supposed to do when a lazy exception is thrown? > > Apart from my ignorance of that exception, I suppose it's better to handle > That exception in your service layer, so you will give to the web layer > A 'proper' collection rather than let the web layer handle that... > > HTH > marco > > > > -----Original Message----- > From: Tom Ziemer [mailto:[EMAIL PROTECTED] > Sent: 30 November 2005 15:39 > To: Struts Users Mailing List > Subject: Re: slightly [OT] Hibernate and domain objects in web apps > > 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 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 >>> >>>--------------------------------------------------------------------- >>>To unsubscribe, e-mail: [EMAIL PROTECTED] >>>For additional commands, e-mail: [EMAIL PROTECTED] >>> >>> >> >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------- Find your next car at Yahoo! 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