java: How to synchronize access to db?

Question

I parse some stuff from a several urls and insert data in database. I want to do this now in parallel. I create a thread pool and run links in separate threads. But it isn't safe. I decided synchronized method that get data from web and save it to database like this:

            synchronized (this) {
                Parser parser = new Parser(link);
                feeds = parser.parse();
                model.insertFeeds(feeds, link);
            }

But this approach blocked access to web and database for other threads until current thread parse data and insert (this is 99% of his work), so it seems that they are perform more than one by one, not as a parallel.

Could you tell what is the better solution for things like this?

I'm not sure what you're really trying to achieve. It's not safe for multiple threads to access the database at the same time, but when they access it sequentially you're upset that it's not parallel? What access pattern are you looking for? — Andrzej Doyle
– Andrzej Doyle, Commented Nov 2, 2012 at 12:44
I would change the methods so they can be run concurrently without synchronization. — Peter Lawrey
– Peter Lawrey, Commented Nov 2, 2012 at 12:44
Please explain what conflict you are trying to prevent. You are generally better off using transactions in DBMS to prevent data conflicts — jalynn2
– jalynn2, Commented Nov 2, 2012 at 12:45
Thanks for your attention. I had a one object in each threaf that do all job that code shows but now I create each own instance in each thread to prevent concurrency. Does it well? — Winte Winte
– Winte Winte, Commented Nov 2, 2012 at 13:25

Aravind Yarram · Accepted Answer · 2012-11-02 12:47:56Z

5

You should let the DB handle the concurrency for you and the way of controlling that is through JDBC transaction isolation levels

answered Nov 2, 2012 at 12:47

Aravind Yarram

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