Spring and DAO w/ Annotation – It works!

I finally got some time to implement the idea that I mentioned in previous blog. After struggling for hours with Spring AOP, I realized I needed CGLIB to proxy abstract class!

It took me a while to learn a bit about Spring's AOP framework. After hours of struggling with words such as Attribute, Definition, Config, Advisor, Source, ObjectSourceDefinition, I finally realized that those were not the problems.

Apparently Spring AOP can only proxy a real instantiated object, i.e. non-abstract class. But the idea is to use the abstract class and let someone else implement it using information provided with @HQL annotation.

So I switched to CGLIB, setting super class to the abstract class, and intercept calls to abstract methods that are annotated.

This is what I get so far….

DAO Code:

public abstract class PersonDAOHibernate
  extends HibernateDaoSupport
  implements PersonDAO
{
  @HQL("from Person p where p.name = :arg1")
  public abstract List<Person> findByName(String name);
  @HQL("from Person")
  public abstract List<Person> findAll();
}

Because the method argument names are not accessible in compiled code, I had the resolve to naming by argument index numbers (starting from 1). I think I'll also add argument/parameter level annotations that can specify parameter names:

@HQL("from Person p where p.name = :name");
public abstract List findByName(@NamedParam("name") String name);

Right now it recognizes return types of List and of the domain class for select/find operations. For updates, it recognizes return types of void and integer (for returning counts)

The Spring configuration currently looks like the following:

<bean id="personDao"
  class="com.nooton.spring.dao.hibernate3.annotation
    .AnnotationHibernateDAOProxyFactoryBean">
  <property name="targetClass"
    value="dao.hibernate.PersonDAOHibernate"/>
  <property name="sessionFactory"
    ref="sessionFactory"/>
</bean>