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I recently had a problem with my application not releasing the database connections when I switched to using JNDI. This was a JEE application that used Spring and Hibernate. Here are the versions that I was using:

• JBoss 4.0.4
• JDK 1.5
• Spring 2.5.5
• Hibernate 3.2.6

Solution

In my Spring applicationContext.xml file, I added the datasource JNDI entry for “Kramerica”. I referenced it in the Hibernate session factory bean:

<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName" value="java:comp/env/jdbc/Kramerica"/>
</bean>
 
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> 
  <property name="dataSource" ref="dataSource"/>
  <property name="hibernateProperties">
    <props>
	<prop key="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</prop>
	<prop key="hibernate.show_sql">false</prop>
	<prop key="hibernate.connection.release_mode">after_transaction</prop>
    </props>
  </property>
</bean>

The key entry is the property “hibernate.connection.release_mode”.
This property specifies when Hibernate should release JDBC connections.

By default, a JDBC connection is held until the session is explicitly closed or disconnected. For an application server JTA datasource, use “after_statement” to aggressively release connections after every JDBC call. For a non-JTA connection, it often makes sense to release the connection at the end of each transaction, by using “after_transaction”.

You can also set it to “auto”, which will choose “after_statement” for the JTA and CMT transaction strategies and “after_transaction” for the JDBC transaction strategy.

You can find more detail on the Hibernate connection settings at the Hibernate site. Happy coding!