What is the common way to write persistent domain classes?

mystic · **Joined:** Tue May 12, 2009 6:08 am **Posts:** 92

What is the common way to write persistent domain classes with hibernate these days? Let's assume we have a project with 100 domain classes. Use a hibernate xml? What about annotations? What ends up being the best/light-weight route to take?

Also, as an aside, what are the common ways to test databases these days? I used to use dbunit, but I found this to be too much work. A necessary evil?

I really want to make applications as fast as my mind thinks (good luck with that one). If there's something that can get me there the closest without having to use grails or something like that, I'd love to hear about it.

Thanks!

Cameron McKenzie · **Posted:** Wed Aug 26, 2009 8:49 am

Check out the Hibernate Tools project. It has some great facilities for reverse engineering hbm files from Java classes - probably your best best for fast generation.

mystic · **Joined:** Tue May 12, 2009 6:08 am **Posts:** 92

Thanks for the reply!

That sounds like a good idea. I already have the domain classes outlined (all the fields).

I heard that people are moving to an ejb3 aproach with spring now. Is that a good solution, or is using the xml mapping file still the best way?

Cameron McKenzie · **Posted:** Wed Aug 26, 2009 10:50 pm

I'm a big fan of annotations. (I wrote a book about Hibernate and JPA Annotations, so I'm biased.)

Still, with a large number of domain classes, there is something to be said to being able to go into just one file and making the appropriate changes, and not have to open up twenty different Java classes and recompile them. So, it's really a matter of just using the best approach for the job.

mystic · **Joined:** Tue May 12, 2009 6:08 am **Posts:** 92

I've been playing with annotations. I like much about them, although embedded objects tend to get a big bloated with all the overriding information.

I am having some trouble with one thing. I have a DomainObject base class that all my objects extend from. This is a common pattern I've used for years. I have used @MappedSuperclass on DomainObject to allow Hibernate to read my properties, and that works. However, I am getting a weird error for the name of the "id" column. It thinks that I am repeating it.

If I get rid of the id in DomainObject and put it in my subclass directly, and then name the column from "id" to "my_class_id", the error goes away.

Is there any way to have the methods and everything in the base class, but then specialize the name of the identifier property in the subclass, or do I need to repeat the id in every domain object?

The reason this is important is that I have some methods in DomainObject that act on the ID... and I guess I'd rather operate on the private variable than abstract property methods.

Code:

@MappedSuperclass
public abstract class DomainObject implements Serializable {

   /* Members */
   @Id
   @GeneratedValue
   @Column( name = "id" )
   protected Long id;

   @Column( name = "is_active" )
   protected boolean isActive = true;

   /* Constructors */

   /* Services */
   public boolean isTransient() {
      return getId() == 0;
   }

   /* Properties */
   public Long getId() {
      return id;
   }

   public void setId( Long id ) {
      this.id = id;
   }

   public boolean isActive() {
      return isActive;
   }

   public void setActive( boolean active ) {
      isActive = active;
   }
}