Hi Dan,
Thank you very much for your detailed and insightful reply. The bookmark
service sounds exactly like what I'm looking for. Also, thanks for the
explanation regarding the DataNucleus enhancer. It now makes much more
sense.
Kind regards,
Nobby
________________________________________
From: Dan Haywood <d...@haywood-associates.co.uk>
Sent: 21 November 2014 06:12 PM
To: users
Subject: Re: Finding entities with JDOQL using cached entities
On 21 November 2014 13:26, Nobby Knox <no...@ecn.co.za> wrote:
Hi everyone,
I'm tying to implement a filter in a JDOQL query using a cached entity in
the where clause, but I'm having some trouble. Here is a quick run down of
my domain models:
<< Owner >>
+ name
+ etc
<< Pet >>
+ name
+ Owner (<- Owner model from above)
In my Pet domain model I have a reference to the Owner object, which I
cache in order to implement future filtering. The problem is that the
original Owner object seems to be some kind of proxy for the actual Owner
object.
It's not a proxy, instead the DataNucleus enhancer modifies the bytecode.
There's a simplified description on the Apache JDO website [1].
When I save the object in the cache, something weird happens and the
properties are set to null.
That happens when the request (ie JDO persistence session) completes. JDO
itself does have various support to allow entities to be detached [2], but
we don't surface that as API within Isis
Is there a way to use a simple POJO (not the enhanced proxy object) in the
where clause in order to implement the filter? Maybe there is another way
to do this? Should I be looking at caching the actual ID (integer value)
and changing the where to something like: where owner_id_OID = :cachedId
Basically, yes, you need to store the identifier for the pojo. One way to
do that (in a very general way) is to use Isis' BookmarkService [3]; use
BookmarkService#bookmarkFor(...) to obtain a serializable Bookmark, and
BookmarkService#lookup to convert back to the pojo.
HTH
Cheers
Dan
[1] http://db.apache.org/jdo/enhancement.html
[2] https://db.apache.org/jdo/attach_detach.html
[3] http://isis.apache.org/reference/services/bookmark-service.html
I hope this makes sense.
?Kind regards,
Nobby
Nobby Knox
Senior Developer
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