committing/persisting without closing the connection.

chillum · **Joined:** Sat Jan 03, 2009 8:03 pm **Posts:** 3

Hello.

i'm relative new to JPA/Hibernate and therefore have following problem:

I leech files, convert em to csv, and load them into a database.

For each leeched file i create a status-object, which holds a list of log-objects. After each step in the process, i create a log-object with some infos and add it to the log-object list within the status-object (each file gets its own status-object).

so on each new log-object within the list, the status-object should be persisted in the database.

so if my app crashes/ a power blackout occurs / a meteor hits the server / etc. ;) there should be the last step logged in the database.

i act as follows:

i create an EntityManager:

Code:

EntityManagerFactory emf;
EntityManager  em; 

public void init(String unitName)
   {
      emf = Persistence.createEntityManagerFactory(unitName);
      em = emf.createEntityManager();
   }

Leech a file and after its local, create a status-object WITHOUT logs and persist it.

Code:

public void persist(Object o)
   {
         em.persist(o);
          em.flush();
   }

After this is done, i start processing the file and after each step i'm creating a log-object and add it to the logs-list within the status-object and call em.flush()

but the flush() saves the changes non-permanent, if my app crashes after the flush() no log would be in the database.

I have to call em.commit() after EACH change in the statusobject (e.g. adding a log) to make it persistent in the DB.
But commit() closes the transaction and i have to reconnect to the DB, search the status-object, add a new log and commit() again, and this for each change/log entry, IMHO thats way to expensive.

I have the feeling that there has to be another solution, i looked up the session-thing, but hibernate just describes making all changes and then commit in the end.
This makes sense in most cases, rollback clears all up etc. But i explicitly want EVERY change directly written into the database.

I would be glad if someone could point me into the right direction :), thanks for it in advance, and thanks for reading to this point :)

sincerely yours,
chillum

Madan_Prabhu · **Posted:** Mon Jan 05, 2009 5:07 am

u may use batch processing for this. for example set jdbc.batch_size=10 in hibernate.cfg.xml file and then if the size of the object reaches to 10, call flush() and clear() method session. it will automatically commit all the objects into DB without calling transaction commit() method.