I've been working with OpenJPA for a while. Don't know why I've never tried to do this before or if it's something new.
That's the idea. You detach an object so it can be passed to a client outside your JVM for modification. In my case it's a the Flash player on a user's browser. Normally the detached state field and detached state manager help to optimize the merge/re-attach process, but in my case the detached state field was being improperly serialized by Flex and BlazeDS. The OpenJPA docs suggest you should be able to merge detached objects without using this field, as long as you're keeping a version field and have primary keys properly setup and identified. I have a rather complex model of linked objects, and merge nested, detached objects fairly regularly in code. Don't know why I haven't noticed this before, but it's occurring on what seems to be a fairly trivial use case. A Date/Timestamp set to null on the top-level object is passed in but not detected during the attach/merge process. Thanks for trying to help, though, and good luck with your own projects. Regards, -jmh On Fri, Aug 21, 2009 at 7:58 AM, Jean-Baptiste BRIAUD -- Novlog<j-b.bri...@novlog.com> wrote: > Are you sure the object is attached or at least merged and only after that > you set the date to null ? > In fact, I'm not, yet:-), OpenJPA expert but it look like the modification > happened when detached and so is ignored. > > On Aug 21, 2009, at 13:37 , Jason Hanna wrote: > >> Yes. Classes are enhanced at build time as a task in the Maven build >> process. >> >> I suspect the issue may be related to the fact I've needed to turn off >> use of the detached state fields in order for the BlazeDS >> serialization to work properly. >> >> -jmh >> >> On Fri, Aug 21, 2009 at 4:26 AM, Jean-Baptiste BRIAUD -- >> Novlog<j-b.bri...@novlog.com> wrote: >>> >>> Hi Jason, >>> >>> How are you enhancing your POJOs ? >>> If you are not enhancing them at build time, please do it and give us >>> some >>> news. >>> >>> On Aug 21, 2009, at 05:38 , jason.m.hanna wrote: >>> >>>> >>>> Hi All, >>>> >>>> I'm having some trouble with my OpenJPA application and could use some >>>> help. >>>> >>>> I've got a web-based application using Flex and BlazeDS to front-end my >>>> web >>>> container running Tomcat, Spring, OpenJPA, and a few other technologies. >>>> My >>>> back-end database is PostgreSQL. >>>> >>>> I've got a DAO layer that works with a number of annotated POJOs, and >>>> everything has been working fairly smoothly until I just tried to merge >>>> a >>>> detached object and set its Date (db timestamp) to null. >>>> >>>> Somewhat surprisingly, the new null value seems to go undetected by JPA >>>> and >>>> the field is never included in the generated update statement. Hence the >>>> date is not removed from my returned object. >>>> >>>> Because I'm using Flex and BlazeDS, my POJOs are annotated to disable >>>> detached state field use. >>>> >>>> I'm running this way as the documentation seemed to suggest this should >>>> work >>>> w/o a detached state field - plus it avoids serialization issues in >>>> BlazeDS >>>> and ActionScript caused by the detached state field. >>>> >>>> Is this a bug I'm seeing or how the system is supposed to work? >>>> >>>> Versions, etc. as follows: >>>> OpenJPA 1.2.1 (classes enhanced @ build) >>>> JDK 1.6.x >>>> PostgreSQL 8.3 >>>> Tomcat 6.x >>>> Flex 3.3 >>>> >>>> Let me know if you need more info. >>>> >>>> Thanks! >>>> -jmh >>>> >>>> >>>> >>>> >>>> -- >>>> View this message in context: >>>> >>>> http://n2.nabble.com/Issue-Merging-Object-w-Null-Timestamp-when-Detached-State-Field-Disabled-tp3484177p3484177.html >>>> Sent from the OpenJPA Users mailing list archive at Nabble.com. >>>> >>> >>> >> > >
