c3p0 Connection Pool not closing connections

Question

I have a Using c3p0 0.9.1.2 , hibernate 3.2.1.ga and spring 2.5.5. The problem is the database connection doesn't close itself. Here are the logs :

[22 mars 2012 12:29:56,091] DEBUG com.mchange.v2.resourcepool.BasicResourcePool ["http-apr-8080"-exec-4] acquire test -- pool is already maxed out. [managed: 20; max: 20] [22 mars 2012 12:29:56,091] DEBUG com.mchange.v2.resourcepool.BasicResourcePool ["http-apr-8080"-exec-4] awaitAvailable(): com.mchange.v2.c3p0.impl.NewPooledConnection@15cc604 [22 mars 2012 12:29:56,091] DEBUG com.mchange.v2.resourcepool.BasicResourcePool ["http-apr-8080"-exec-4] trace com.mchange.v2.resourcepool.BasicResourcePool@6b0524 [managed: 20, unused: 0, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@15cc604)

Here's the datasource configuration :

<!-- Local DataSource that works in any environment -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
    <property name="driverClass" value="${database.driver}"/>
    <property name="jdbcUrl" value="${database.url}"/>
    <property name="user" value="${database.user}"/>
    <property name="password" value="${database.password}"/>
    <!--<property name="connectionCustomizerClassName" value="org.xxx.webapp.common.persistence.WatchConnectionCustomizer"/>-->
    <property name="maxStatements" value="500"/>
    <property name="maxIdleTime" value="1800"/>
    <property name="maxPoolSize" value="100"/>
    <property name="minPoolSize" value="2"/>
    <property name="initialPoolSize" value="2"/>
    <property name="acquireIncrement" value="3"/>
    <property name="idleConnectionTestPeriod" value="3000"/>
</bean>



<bean id="sessionFactory"
    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" >
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">${hibernate.dialect}</prop>
            <prop key="hibernate.show_sql">false</prop>
            <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop>
            <prop key="hibernate.connection.autocommit">${hibernate.connection.autocommit}</prop>
            <prop key="hibernate.transaction.auto_close_session">${hibernate.transaction.auto_close_session}</prop>
            <prop key="hibernate.connection.release_mode">${hibernate.connection.release_mode}</prop>
            <prop key="hibernate.bytecode.use_reflection_optimizer">${hibernate.bytecode.use_reflection_optimizer}</prop>
            <prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop>
            <prop key="hibernate.cache.use_query_cache">true</prop>
            <prop key="hibernate.cache.use_second_level_cache">true</prop>
            <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.EhCacheRegionFactory</prop>
        </props>
    </property>

 <property name="annotatedClasses">
    <list>
        ...
   </list>
    </property>

   <property name="dataSource">
    <ref bean="dataSource" />
   </property>


</bean>

<bean id="transactionManager"
    class="org.springframework.orm.hibernate3.HibernateTransactionManager">
    <property name="sessionFactory">
        <ref bean="sessionFactory" />
    </property>
</bean>

Here's our generic Dao

public class GenericDAO<T, PK extends Serializable> extends HibernateDaoSupport
    implements IGenericDAO<T, PK> {

private Class<T> clazz;
private Logger logger = Logger.getLogger(GenericDAO.class);
private static Session session;

public GenericDAO(Class<T> clazz) {
    this.clazz = clazz;
}

public void refresh(T instanceToRefresh) throws DataAccessException {
    getHibernateTemplate().refresh(instanceToRefresh);
    //getCurrentSession().refresh(instanceToRefresh);
}

public void saveOrUpdate(T instanceToSaveOrUpdate)
        throws DataAccessException {
    //getCurrentSession().saveOrUpdate(instanceToSaveOrUpdate);
    getHibernateTemplate().saveOrUpdate(instanceToSaveOrUpdate);
}

public void persist(T instanceToPersist) throws DataAccessException {
    getHibernateTemplate().persist(instanceToPersist);
    //getCurrentSession().persist(instanceToPersist);
}

@SuppressWarnings("unchecked")
public T merge(T instanceToMerge) throws DataAccessException {
    T instanceMerged = (T) getHibernateTemplate().merge(instanceToMerge);
    //T instanceMerged = (T) getCurrentSession().merge(instanceToMerge);
    return instanceMerged;
}

@SuppressWarnings("unchecked")
public PK save(T newInstance) throws DataAccessException {
    return (PK) getHibernateTemplate().save(newInstance);
    //return (PK) getCurrentSession().save(newInstance);
}

public void delete(T persistentObject) throws DataAccessException {
    getHibernateTemplate().delete(persistentObject);
    //getCurrentSession().delete(persistentObject);
}

@SuppressWarnings("unchecked")
public T load(PK id) {
    return (T) getHibernateTemplate().get(clazz, id);
    //return (T) getCurrentSession().get(clazz, id);
}

public void update(T transientObject) throws DataAccessException {
    //getCurrentSession().update(transientObject);
    getHibernateTemplate().update(transientObject);
}

@SuppressWarnings("unchecked")
public List<T> loadAll() throws DataAccessException {
    //Session session = this.getCurrentSession();
    //return session.createQuery("from " + clazz.getName()).list();
    return getHibernateTemplate().loadAll(clazz);
}
}

Thanks in advance.

Answer 1

Normally, the connection is automatically closed by hibernate. However, a few things to note:

• long-running transactions may occupy a connection
• improper session management may mean you don't close your session, which in turn means the connection remains in use

The typical setup when using spring is to annotate your service methods with @Transactional. That way spring will manage your transactions and sessions.