Hi,

My problem doesn't solved.

I run a client program that load each iterate 300 hibernate objects using Query.list(). Unfortunatly, after a while, I got OutOfMemoryError.
I ran it many times and it always fails after around 2400 iterations.
I watched it through JProfiler and I saw that the used heap size growes significantly during this time and the GC couldn't release enough memory.

The sequence of the process is (300 entities in each iteration):
1. Load the entities (relevant code attached below)
2. Do some business
3. Update the entities

I use Jboss 3.2 and Hibernate3.
1. I'm using CMT(container managed transactions) therfore ther is no transactions in the code.


The hibernate code:
Session session = null;

try {

session = openSession();

Query query = prepareHQLQuery(session, hqlQuery, boundedVariables);

return query.list();

} catch (HibernateException hibEx) {
logger.error("Failed to get list of entities", hibEx);
throw new PersistencyException("Failed to get list of entities");
} finally {
closeSession(session);
}


code of the update:

Session session = null;
PersistentEntity entity = null;

try {
session = openSession();
} catch (HibernateException hiberEx) {
logger.error("Failed to open session", hiberEx);
throw new PersistencyException();
}

for (int i=0;i<entities.length;i++) {
entity = entities[i];

try {

session.update(entity);


} catch (HibernateException hibEx) {
logger.error("Failed to update entity with ID "
+ entity.getId().longValue() + " at the storage", hibEx);

if (!proceedOnError) {

try {
session.flush();

closeSession(session);
} catch (Exception ex) {
logger.warn("Failed to flush connection", ex);
}

try {
closeSession(session);
} catch (Exception ex) {
logger.warn("Failed to close connection to storage", ex);
}

throw new PersistencyException("failed to update Entity of type "
+ entity.getClass().getName());

}

}
}

try {

session.flush();

} catch (HibernateException hiberEx) {
logger.error("Failed to commit changes while updating entities", hiberEx);
throw new PersistencyException();
} finally {
closeSession(session);
}


As I wrote, through the JProfiler I saw that query.list() method doesn't release the memory.

What is the trap in my code??

Thank you very much!

If you're doing everything in the same transaction the first-level cache will keep a reference to every object loaded by your query.

This page on batch processing shows how to avoid out of memory errors by using the session.clear() method to release objects from the first-level cache.

http://www.hibernate.org/hib_docs/reference/en/html/batch.html

Take a look at the JavaDoc for the Hibernate org.hibernate Session:




http://www.hibernate.org/hib_docs/v3/api/org/hibernate/Session.html#clear()

I must say that during my tests I try the fillowing advices:

1. session.setCacheMode(CacheMode.IGNORE) before loading
2. session.clear() after I loaded the entities.
3. sessionFactory.evict(Class myLoadedClasses)
4. sessionFactory.evictQueries()


No change and no progress! It always failes around the same amount