applicationContext.xml with datasource or hibernate.cfg.xml. Difference?

Question

Want to clear some confusion. I have applicationContext.xml.

Question 1: Whats the difference between 1 & 2. Are they both same with different approach?

Question 2:

I asked question on Spring forum regarding some problem. Onething he mentioned about pooling is below

if you need/want to use the internal connection pooling for hibernate I would advice against it and simply configure a datasource which supports connection pooling and inject that into your sessionfactorybean.

internal connection pooling for hibernate = This is number 2 below. Right?

simply configure a datasource which supports connection pooling and inject that into your sessionfactorybean = This is number 1 below. right?

1# -

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="${jdbc.driverClassName}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <property name="maxActive" value="100"/>
        <property name="maxIdle" value="30"/>
        <property name="maxWait" value="16000"/>
        <property name="minIdle" value="0"/>
    </bean>

 <!-- Hibernate SessionFactory -->
    <bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="annotatedClasses">
            <list>
                <value>com.mkyong.customer.model.Customer</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">false</prop>
                <prop key="hibernate.generate_statistics">true</prop>
            </props>
        </property>
    </bean>

2# -

Pooling and connection info is in hibernate.cfg.xml

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

Solution 1

Answer 1:

Both approaches are the same. By default , hibernate reads the configuration from classpath:hibernate.cfg.xml to build SessionFactory . LocalSessionFactoryBean just allows you to setup hibernate configuration inside applicationContext.xml instead of hibernate.cfg.xml .

If a same property is specified in both files , depending on the property , it will has addictive effect or the properties specified in applicationContext.xml will take higher priority such that those values in hibernate.cfg.xml will be ignored.

For method 1, annotatedClasses and hibernateProperties should have the addictive effect with the corresponding values in hibernate.cfg.xml . The DBCP dataSouruce in applicationContext.xml should cause the related properties in hibernate.cfg.xml being ignored.

Answer 2:

For method 2 , if you don't specify any properties of LocalSessionFactoryBean , all the hibernate configurations are specified by the hibernate.cfg.xml. If there are no connection pool configured in hibernate.cfg.xml , hibernate's own connection pooling algorithm is used by default , which is quite rudimentary and not intended for use in a production system, or even for performance testing.

Solution 2

If what you want is to build a session factory, you will get the same result with both approaches. I don't think one can do more than the other.

In my opinion, you would use the hibernate.cfg.xml approach when you are not using Spring. When JUnit testing your DAOs for example. Not having to build a Spring application context makes your tests run faster.

However, when you are using Spring, I think it's a good thing to keep your datasource separated from the session factory. You are using Spring for dependency inject, right? Why not using spring to give your session factory what it needs?

Comments

[Jono]

Hi, i too am confused on which approach to use. i think i will go for the cfg.xml as this seperates and decouples the hibernate config away from this applicationContext making it easier to create multiple data config sources.

[Pirzada]

Thanks. What do you mean by "Why not using spring to give your session factory what it needs?"

[Alban]

I mean, inject the datasource into your session factory, as you would inject a dao into a service, or a service into a controller. It gives you the same benefits: you integrate components at one place: the application context. You need to switch to alternative datasource implementation, you know where to look. You could even choose which datasource implementation to inject using property placeholders.