休眠-连接过多

Question

I have a RESTful API which I am using for an Android application. Everything is working fine but after some time I run out of connections on the database.

I am monitoring the Client Connections using MySQL Workbench and everytime I log a user in, the connection number increases. (None of them are being re-used or closed).

Here is my example Select query to get a users information based on his authentication token:

    Session session = HibernateUtil.getSessionFactory().openSession();

    String sql = "SELECT * FROM user WHERE token = :token";
    SQLQuery query = session.createSQLQuery(sql);
    query.addEntity(User.class);
    query.setParameter("token", authToken);
    List results = query.list();

    if(results.isEmpty()){
        session.close();
        return null;
    }
    else {
        session.close();
        return (User) results.get(0);
    }

The HibernateUtil.java class is set up as follows:

public class HibernateUtil {
private static SessionFactory sessionFactory;
private static ServiceRegistry serviceRegistry;

public static SessionFactory createSessionFactory() {
    Configuration configuration = new Configuration();
    configuration.configure();
    serviceRegistry = new ServiceRegistryBuilder().applySettings(
            configuration.getProperties()). buildServiceRegistry();
    sessionFactory = configuration.buildSessionFactory(serviceRegistry);
    return sessionFactory;
}

public static SessionFactory getSessionFactory() {
    if(sessionFactory != null)
        return sessionFactory;
    else
        return createSessionFactory();
}

Even though I am doing session.close(); the client connections keep increasing until the MySQL treshold is reached and it gives me the error of Too Many Connections.

I have looked around a lot to try and find an answer but nothing seems to have helped... Any guidance is appreciated!

Thanks Mike

EDIT:

Here is my configuration file (hibernate.cgf.xml)

 <property name="hibernate.current_session_context_class">org.hibernate.context.internal.ThreadLocalSessionContext</property>
    <property name="hibernate.c3p0.min_size">0</property>
    <property name="hibernate.c3p0.max_size">1</property>
    <property name="hibernate.c3p0.acquire_increment">1</property>
    <property name="hibernate.c3p0.idle_test_period">3000</property>
    <property name="hibernate.c3p0.max_statements">50</property>
    <property name="hibernate.c3p0.timeout">1800</property>
    <property name="hibernate.c3p0.maxConnectionAge">0</property>

Answer 1

Set the connection pooling properties in the hibernate configuration file. For connection pooling refer this link.

In addition to that, you can write your own connection closing logic as follows:

private void closeSessionFactory(SessionFactory factory) { 
   if(factory instanceof SessionFactoryImpl) {
      SessionFactoryImpl sf = (SessionFactoryImpl)factory;
      ConnectionProvider conn = sf.getConnectionProvider();
      conn.close();
   }
   factory.close();
}

Let me know if that solves your issue.

Answer 2

put these in your configuration xml and try,

<prop key="hibernate.connection.release_mode">after_statement</prop>
<prop key="hibernate.transaction.auto_close_session">true</prop>