How about obtaining session through connection pooling

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

Hi folks,

I worry now about the approach of obtaining session which confirmed available connection pooling with c3p0.
Is the connection pool available by the Singleton-Pattern used in order to get session ? (for example, HibernateUtil.java in 'Hibernate2 Reference Documentation')
It seems that only one connection is always reused.
How should the approach of session obtaining for using a connection pooling effectively be realized?

Is the following approach inappropriate?

Code:

public class HibernateUtil2 {
    private static ThreadLocalSession session = null;
 
    private static class ThreadLocalSession extends ThreadLocal {
        public Object initialValue() {
            System.out.println("invoked : ThreadLocalSession#initialValue()");
            Session ss = null;
            try {
                ss = new Configuration().configure().buildSessionFactory()
                    .openSession();
            }
            catch (HibernateException e) {
                e.printStackTrace();
            }
            return (ss);
        }
    }


    public static Session currentSession() {
        session = new ThreadLocalSession();
        return (Session) session.get();
    }


    public static void closeSession() throws HibernateException {
//            Session s = (Session) session.get();
//        session.set(null);
//        if (s != null) s.close();
    }

}

michael · **Posted:** Tue Apr 20, 2004 7:17 pm

I don't understand your problem, why don't you use the proven ThreadLocal pattern used in many samples and tutorials?

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

I thank to your reply.
That is, can the Singleton pattern using ThreadLocal obtain a session from connection-pool appropriately?
If it which I feel like a problem is overanxiety, it is a good thing(no problems) .

The my first code referred to the tutorial:

Code:

public class HibernateUtil {
    private static HibernateUtil hibernateutilInstance__ = null;
    private static SessionFactory sessionfactoryInstance__ = null;
    private static final ThreadLocal threadlocalSession__ = new ThreadLocal();

    public static Session getCurrentSession() throws HibernateException {

        if (hibernateutilInstance__ == null) {
            hibernateutilInstance__ = new HibernateUtil();
        }

        Session sessionCurrent = (Session) threadlocalSession__.get();

        if (sessionCurrent == null) {
            if (sessionfactoryInstance__ == null) {
                sessionfactoryInstance__ = new Configuration().configure()
                    .buildSessionFactory();
            }
            sessionCurrent = sessionfactoryInstance__.openSession();
            threadlocalSession__.set(sessionCurrent);
        }
        if (!sessionCurrent.isOpen()) {
            sessionCurrent = sessionfactoryInstance__.openSession();
        }
        return sessionCurrent;
    }


    public static void closeCurrentSession() throws HibernateException {
        Session s = (Session) threadlocalSession__.get();
        threadlocalSession__.set(null);
        if (s != null) s.close();
    }
}

and config file(hibernate.cfg.xml):

Code:

<property name="c3p0.min_size">1</property>
<property name="c3p0.max_size">3</property>
<property name="c3p0.max_statements">10</property>
<property name="c3p0.timeout">100</property>
<property name="c3p0.validate">true</property> 
<property name="hibernate.connection.provider_class">net.sf.hibernate.connection.C3P0ConnectionProvider</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/testdb?useUnicode=true&amp;characterEncoding=SJIS</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.connection.pool_size">2</property>
<property name="hibernate.dialect">net.sf.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">update</property>

In above HibernateUtil class, when I use getCurrentSession() method which obtained session is from connection pool?

Best regards,
thx.
[/code]

michael · **Posted:** Wed Apr 21, 2004 5:13 am

Hi, the Session is never from the Pool, only the underlying JDBC connection is from the pool. There is no need to pool Sessions, as they are very lightweight.

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

I thank to your reply.
As for my application, many db-connection is predicted.
In such a case, if Hibernate is used, isn't there necessity of using a pool explicit?
How should I do the implementing if I need connection pooling?
Are the pointers to reference implementation anywhere?

Best regards,
Sho

michael · **Posted:** Fri Apr 23, 2004 7:50 am

You are already using connection pooling in the config file you posted. I dont get your problem.

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

Hi, michael.

Thank you very match your explanation.
I understand that I have no need especially implementation for pooling.

But I want to understand detailed mechanism of association between connection-pooling and hibernate-sessions.
Is there documents(URL) explained in detail about this matter?

Anyway, I thank to you.

anthony · **Posted:** Fri Apr 23, 2004 8:19 am

hibernate session contains persistant objects + is a object oriented tool to query your domain model.

It transform object query in SQL and tranform the resultset in loaded objects.

For querying and persisting, it needs a jdbc connection that is obtained by the configured pool. The session also offers "transaction management" which is the same as pure jdbc transaction.

Now if you want detailed mechanism, you can debug or read the sources....

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

Hi, delpouve.

thx your information.
Is Hibernate session object using pooled JDBC-connection if I configured it in config-file?
For the moment, this is the my last question.

Best regards.
Sho

christian · **Posted:** Sun Apr 25, 2004 10:42 pm

Why don't you read the documentation?

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

I red documentation that is chapter3(3.2-3.4) in 'Hibernate2 Reference Documentation'.
and, I succeeded to use pooled connection:

Code:

SessionFactory sessions = cfg.buildSessionFactory();
Session sess = sessions.openSession();

If I want to use pooled session, should I use above code every time when getting the session?

very thx.

christian · **Posted:** Sun Apr 25, 2004 11:48 pm

You should never pool sessions, because this is not how Hibernate is used. Read some of the articles/tutorials about Hibernate or the documentation.

sho · **Joined:** Mon Apr 19, 2004 11:27 pm **Posts:** 9

Thanx.
I peruse tutorial/article/docs again.
I thank to having spent your time about my question.