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Re: [eclipselink-users] Strange persistence layer behaviour 
Hello,
A common problem when using a bidirectional relationship is setting one side of the relationship but not the other. This problem will occur if your application is setting the LetterOfCreditGoederenOmsRegel.goederenOms but not adding the LetterOfCreditGoederenOmsRegel to the LetterOfCreditGoederenOms's collection of LetterOfCreditGoederenOmsRegel. Because the provider uses a cache, the LetterOfCreditGoederenOms returned from the find does not have its collection set until it is refreshed from the database
Both sides of the relationship need to be set as JPA does not provide relationship maintenance to keep the cache insynch with what is in the database. 
Best Regards,
Chris

Willem Kunkels wrote:


Hi all,
I have come across something that I do not quite understand, maybe someone can shed a light... 

Here is the situation:
The entity LetterOfCreditGoederenOms contains lines wich can be retrieved through the following mapping:
@OneToMany(cascade=CascadeType./REFRESH/, mappedBy = "goederenOms", fetch = FetchType./LAZY/) 
    *private* Collection<LetterOfCreditGoederenOmsRegel> regels;

    *public* Collection<LetterOfCreditGoederenOmsRegel> getRegels() {
        *return* regels;
    }
I have a bean that contains logic to compare two objects and determine changes between the two. In one case I check whether I need to remove something from the database. If so, I do the following:
omschrijving = getEm().find(LetterOfCreditGoederenOms.*class*, *new* LetterOfCreditGoederenOmsPK(omschrijving.getVolgnummerInkooporder(), omschrijving.getInkoopOrderNr(), omschrijving.getInkoopOrderRegelNummer())); 
                    getRemovedObjects().add(omschrijving);
getRemovedObjects().addAll(omschrijving.getRegels()); What I would expect (now that the LetterOfCreditGoederenOms object 'omschrijving' is managed) is that the call to getRegels() will get me the lines associated with the omschrijving object. It does not do this. What I need to do to get this working is adding the following just after the find: 

                        // A little note:
// You would expect that the regels can be retrieved by // calling the getRegels() method. For some reason unknown, // the persistence layer does not do this. The only way // to get the regels is a refresh of the object we just // found: cascading refresh then does get the regels... 
                        // weird...
                        getEm().refresh(omschrijving);

Anyone's got an answer to this enigma?

Cheers,

Willem Kunkels
Java Developer

Koopman International BV
Distelweg 88
1031 HH  Amsterdam
The Netherlands
Tel.: +31 20 494 7 893
www.koopmanint.com
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