Re: [eclipselink-users] Refreshing lists

[Tim Hollosy <hollosyt@xxxxxxxxx>]

You'll want to turn off shared caching:

http://wiki.eclipse.org/EclipseLink/Examples/JPA/Caching

That should solve your issues with the cached list.

The reason you see the same statement over and over again is that you
a relationship without a @JoinFetch annotation, if you add a
@JoinFetch with an outer join type eclipselink will generate a left
join for you, eliminating the extra fetching.

./tch



On Mon, May 24, 2010 at 4:56 PM, Christopher Piggott <cpiggott@xxxxxxxxx> wrote:
> Hi,
>
> I am working on a small project that involves jersey (jax-rs), JPA
> (provided by eclipselink), and guice.  My jersey resources are created
> by guice, which also injects an EntityManager into them.  There is
> just one EntityManagerFactory instance, and it is owned by the
> injector.
>
> The resource then, for every request, creates an EntityManager, gets a
> List<Item>, and sends the result back as the response.
>
> The resource looks like this:
>
>
> @Path("/list")
> public class MyResource {
>    @Inject @Named("MyTestEntity")
>    private EntityManager em;
>
>    @GET
>    @Produces("text/plain")
>    public String getIt() {
>        log.debug("returning something");
>
>        if(em == null) {
>            return "no database";
>        } else {
>            Query q = em.createNamedQuery("Item.findAll");
>            List<Item> items = q.getResultList();
>            StringBuilder sb = new StringBuilder();
>            for(Item p : items)
>            {
>                sb.append(p.getPlatformId() + "\n");
>            }
>
>            em.close();
>            return sb.toString();
>        }
> }
>
>
> Here's the thing I'm not getting.  When I do the first query it takes
> a fairly long time as it gathers up all the data.  When I do the
> second and subsequent queries it takes no time at all.  It doesn't
> consult the database at all; it just looks in the cache.
>
> I can see how to do en.refresh(anItem) but what I want to do is cause
> it to refresh the ENTIRE LIST.  The problem is, this web service isn't
> the only thing accessing this data - external applications are
> constantly adding and updating records.
>
> I can set a queryHint that causes a refresh, but it seems that's not
> really the right thing to do.  For one, that would be
> eclipse-specific, and the whole point of me using JPA is to avoid
> implementation-specific APIs (even thought I can't really see myself
> using anything other than eclipselink in the near future).
>
>
> I have looked all over but have yet to find a clear example of how
> this is supposed to work in, say, a grizzly or tomcat environment.  I
> want to maximize performance, meaning pooling connections etc.
>
>
> The other problem I have is that, according to logs, it seems to
> prepare the same statements over and over and over ... unless for some
> reason         p.put("eclipselink.logging.level.sql", "FINE") is lying
> to me.  It doesn't seem to be... it really does seem to generate a LOT
> of traffic to retrieve relatively simple things.  It's a fully linked
> database with many relationships; still...
>
>
> --Chris
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