Why configure both dataSource and sessionFactory in Spring-Hibernate Configuration?

Question

I'm using Spring 3.1.2 and Hibernate 4.1.7 for my web application. I want to now configure both of these. I have my hibernate.cfg.xml file:

<hibernate-configuration>
    <session-factory>
        <property name="connection.url">jdbc:mysql://localhost:3306/test</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.pool_size">10</property>
        <property name="hibernate.connection.autocommit">false</property>
        <property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
        <!-- 
        <property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
         -->
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">update</property>       
    </session-factory>
</hibernate-configuration>

My webapp-servlet.xml spring config file:

<beans>
<bean id="sessionFactory"
    class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="configLocation">
        <value>
            classpath:hibernate.cfg.xml
        </value>
    </property>
    <property name = "dataSource" ref = "dataSource"></property>
</bean>

<bean id = "dataSource" class = "org.apache.commons.dbcp.BasicDataSource">
    <property name = "driverClassName" value = "com.mysql.jdbc.Driver" />
    <property name = "url" value = "jdbc:mysql://localhost:3306/test" />
    <property name = "username" value = "root" />
    <property name = "password" value = "root" />
    <property name = "maxActive" value = "10" />
</bean>
</beans>

1. Why do I need to configure a DataSource bean when all of the data needed is already included in the hibernate configuration file? Does Hibernate have some default it can use?
2. What are some other DataSources I can use?
3. Am I missing any other beans or configuration parameters/properties to get hibernate working with my application?

Answer 1

1. You don't need both of them. You can either get rid of hibernate.cfg.xml and configure everything in LocalSessionFactoryBean, or reuse your existing hibernate.cfg.xml as is (in this case you don't need to configure DataSource in Spring config).

2. You have the following options:

   • Use embedded database - it's good for testing and learning purposes

   • Use DriverManagerDataSource - it's a simple non-pooled datasource that can be used for testing, etc (not recommended for production use)

   • Use connection pool such as DBCP or c3p0

   • If you deploy to application server you can use connection pool provided by the application server using JNDI
     
     

3. Your current configuration is sufficient, but it lacks support of Spring transaction management. In order to enable it you need to

   • Declare HibernateTransactionManager

   • Add <tx:annotation-driven> to enable declarative transaction management (@Transactional)

   • Declare TransactionTemplate if you want to use programmatic transaction management (use it to overcome limitations of declarative transaction management)

   • Also don't forget to remove transaction-related properties from Hibernate configuration since they may conflict with Spring transaction management