Injecting fields via Spring into entities loaded by Hibernate

Question

I am looking for a way to inject certain properties via Spring in a bean that is loaded from the DB by Hibernate.

E.g.

class Student {
   int id; //loaded from DB
   String name; //loaded from DB
   int injectedProperty; //Inject via Spring
}

Can I configure Spring so that whenever Hibernate creates objects of class Student, some properties as defined in some applicationContext file are injected with the object creation?

Answer 1

While the aspectj way works, I'd say the standard spring / hibernate way is to register a LoadEventListener (read more in the hibernate core reference, the spring reference and this thread)

here is a snip from the spring sessionfactory bean definition

<bean id="mySessionFactory"
    class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
    ...
    <property name="eventListeners">
        <map>
            <entry key="post-load">
                <bean class="com.foo.spring.MyLoadListener"></bean>
            </entry>
        </map>
    </property>
</bean>

and here is the LoadEventListener:

public class MyLoadListener implements LoadEventListener{

    public void setSpringManagedProperty(String springManagedProperty){
        this.springManagedProperty = springManagedProperty;
    }
    private String springManagedProperty;

    @Override
    public void onLoad(LoadEvent event, LoadType loadType) throws HibernateException{
        if(MyEntity.class.getName().equals(event.getEntityClassName())){
            MyEntity entity = (MyEntity) event.getInstanceToLoad();
            entity.setMyCustomProperty(springManagedProperty);
        }

    }

}

Look mom, no aspectj needed.

Answer 2

There is a facility for this, using AspectJ class weaving with the @Configurable annotation. This will auto-wire any new instance of an annotated class with Spring dependencies, including objects instantiated via reflection using the likes of Hibernate.

It does require some class-loading magic, and so depends on compatibility with your server platform.