Spring Hibernate Database Connections

Question

I am in the process of learning Hibernate, Spring and JPA.

I would like to know whether my database connections are closed automatically by Spring or not. When I looked at database table v$session I can find there are four JDBC Thin Client sessions. So would like to know whether these connections are from my application.

Below is my applicationContext.xml. Any help is highly appreciable.

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd"
>   
    <context:component-scan base-package="net.test" />
    <!-- Data Source Declaration -->    
    <bean id="DataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="jdbc/myDS"/>     
</bean>
    <bean
        class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />
    <bean class="org.springframework.orm.hibernate4.HibernateExceptionTranslator" />
    <!-- JPA Entity Manager Factory -->
    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="DataSource" />
        <property name="packagesToScan" value="net.test.entity" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="showSql" value="true" />
                <property name="generateDdl" value="false" />
                <property name="databasePlatform" value="${jdbc.dialectClass}" />
            </bean>
        </property>
    </bean>
    <bean id="defaultLobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler" />
    <!-- Session Factory Declaration -->
    <bean id="SessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="DataSource" />
        <property name="annotatedClasses">
            <list>
                <value>net.test.entity.Employee</value>
                <value>net.test.entity.Department</value>

            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.query.factory_class">org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory
                </prop>
            </props>
        </property>
    </bean> 
    <tx:annotation-driven transaction-manager="txManager" />
    <tx:annotation-driven transaction-manager="transactionManager" />   
    <bean id="txManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="SessionFactory" />
    </bean>

    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
    </bean>
    <!-- <tx:annotation-driven transaction-manager="txManager"/> -->
    <context:annotation-config />
    <bean id="hibernateStatisticsMBean" class="org.hibernate.jmx.StatisticsService">
        <property name="statisticsEnabled" value="true" />
        <property name="sessionFactory" value="#{entityManagerFactory.sessionFactory}" />
    </bean>
    <bean name="ehCacheManagerMBean"
        class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" />
    <bean id="mbeanServer" class="org.springframework.jmx.support.MBeanServerFactoryBean">
        <property name="locateExistingServerIfPossible" value="true" />
    </bean>
    <bean id="jmxExporter" class="org.springframework.jmx.export.MBeanExporter"
        lazy-init="false">
        <property name="server" ref="mbeanServer" />
        <property name="registrationBehaviorName" value="REGISTRATION_REPLACE_EXISTING" />
        <property name="beans">
            <map>
                <entry key="SpringBeans:name=hibernateStatisticsMBean"
                    value-ref="hibernateStatisticsMBean" />
                <entry key="SpringBeans:name=ehCacheManagerMBean" value-ref="ehCacheManagerMBean" />
            </map>
        </property>
    </bean>
</beans>

Answer 1

Spring closes connections when the transaction is committed of rollbacked. But the connections are pooled connections, so closing them simply puts them back into the pool of connections, and doen't physically closes them.

The first goal is to be able to get a new connection from the pool extremely quickly, without having to recreate a new physical connection each time, because it's a costly operation.

The other goal is to be able to put a limit on the number of opened connections, to avoid bringing the database to its knees.

Note that the pool of connections, in your case, isn't handled by Spring, but by your application server, which makes it available from JNDI.