Hibernate causes out of memory exception when saving large number of entities

In my application I'm using CSVReader & hibernate to import large amount of entities (like 1 500 000 or more) into database from a csv file. The code looks like this:

        Session session = headerdao.getSessionFactory().openSession();
        Transaction tx = session.beginTransaction();

        int count = 0;
        String[] nextLine;

        while ((nextLine = reader.readNext()) != null) {
            try {

                if (nextLine.length == 23
                        && Integer.parseInt(nextLine[0]) > lastIdInDB) {
                    JournalHeader current = parseJournalHeader(nextLine);
                    current.setChain(chain);
                    session.save(current);
                    count++;
                    if (count % 100 == 0) {
                        session.flush();
                        tx.commit();
                        session.clear();
                        tx.begin();
                    }
                    if (count % 10000 == 0) {
                        LOG.info(count);
                    }

                }

            } catch (NumberFormatException e) {
                e.printStackTrace();
            } catch (ParseException e) {
                e.printStackTrace();
            }

        }
        tx.commit();
        session.close();

With large enough files (somewhere around 700 000 lines) I get out of memory exception (heap space).

It seems that the problem is somehow hibernate related, because if I comment just the line session.save(current); it runs fine. If it's uncommented, the task manager shows continuously increasing memory usage of javaw and then at some 开发者_如何学JAVApoint the parsing gets real slow and it crashes.

parseJournalHeader() does nothing special, it just parses an entity based on the String[] that the csv reader gives.

Session actually persists objects in cache. You are doing correct things to deal with first-level cache. But there's more things which prevent garbage collection from happening.

Try to use StatelessSession instead.