Gday - They're talking about the DataCache. Check out the docs here:
http://openjpa.apache.org/docs/latest/manual/ref_guide_caching.html
In your scenario, you might want to disable the datacache, or employ
datacache timeouts or eviction.
cheers!
.droo.
On 15/05/2008, at 8:52 PM, Alexandros Karypidis wrote:
Hi,
First of all, thanks for the input.
1) I am not sure what the second-level cache is. Going through the
user manual and searching the web did not help. All I could find
that is cache-related are the following properties, which I set as
follows (hoping that they indeed control the "second-level cache"):
<property name="openjpa.DataCache" value="false"/>
<property name="openjpa.QueryCache" value="false"/>
2) As far as calling evict is concerned, I added these calls between
the two find() calls:
OpenJPAEntityManagerFactory jemFactory =
(OpenJPAEntityManagerFactory) emFactory;
jemFactory.getQueryResultCache().evictAll();
jemFactory.getStoreCache().evictAll();
OpenJPAEntityManager jem = (OpenJPAEntityManager) em;
jem.evictAll(Record.class);
Neither modification helped and as far as the second approach is
concerned, I would prefer to restrict my code to standard JPA only.
In any case OpenJPA still uses some cache to return the object the
second time around.
Can you point me towards something more concrete regarding this
"second level cache" and how to disable it? Is it perhaps referred
to by some other name? I really couldn't find information when web-
searching for stuff like "openjpa second level cache".
Thanks again for your time.
Craig L Russell wrote:
Hi,
It sounds like you're using the second-level cache which is
dutifully returning the current contents that are cached.
Have you tried using the evict methods of the second level cache,
or disabling it for the application?
Craig
On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
Hi,
First of all, I've done research through the archives for the
situation I am facing and found this:
http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/[EMAIL
PROTECTED]
I am facing the exact problem mentioned in that thread: I need to
fetch an object several times from the database, whose columns are
updated from another program and pick up the changes made by that
program. However, I can't get OpenJPA to re-execute SQL and
retrieve the object's new data from the database.
In the thread of the link I provide, I was lead to believe that
em.refresh(obj) should do the trick. However, OpenJPA does not
execute any SQL (I have SQL=TRACE in the log options and I only
see one select statement) and keeps the old data in the object.
I use OpenJPA release 1.0.2 and the code snippet with which I test
is the following:
=========================================================
EntityManagerFactory emFactory =
Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
EntityManager em = emFactory.createEntityManager();
Record r = em.find(Record.class, 1);
System.out.println("VALUE: " + r.getStrField());
System.out.print("PRESS ENTER TO REDISPLAY...");
BufferedReader stdin = new BufferedReader(new InputStreamReader(
System.in));
stdin.readLine();
// ------> PROBLEM AREA <------
em.refresh(r); // does not work
// ((OpenJPAEntityManager)em).evict(r); // also does not work
// em.clear(); // works but detaches everything
// em.close(); // ... re-create. works, costs too much
// ------> PROBLEM AREA <------
r = em.find(Record.class, 1);
System.out.println("VALUE: " + r.getStrField());
=========================================================
I change the strField of the "Record" object using a database
editor before I press enter to re-fetch the value.
So, my question is, why does OpenJPA ignore the call to refresh()
if the object is still attached? I don't see it as reasonable to
detach all objects just to pick up a change in the database. I
figured it may be a transaction isolation issue, but then did the
following test which also did not work:
=========================================================
EntityManagerFactory emFactory =
Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
EntityManager em = emFactory.createEntityManager();
em.getTransaction().begin();
Record r = em.find(Record.class, 1);
System.out.println("VALUE: " + r.getStrField());
em.getTransaction().commit();
System.out.print("PRESS ENTER TO REDISPLAY...");
BufferedReader stdin = new BufferedReader(new InputStreamReader(
System.in));
stdin.readLine();
em.getTransaction().begin();
r = em.find(Record.class, 1);
em.refresh(r);
em.getTransaction().commit();
System.out.println("VALUE: " + r.getStrField());
=========================================================
So even when reading the object through 2 different transactions,
I still can't get its data to be re-fetched...
Funilly enough, if i call rollback() on the transaction, it does
work! However, it seems too much of a kludge to base my solution
on that...
Thanks in advace to anyone who takes the time to help out.
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/
jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!
