Handling subclasses of persistent classes

damonf · **Joined:** Wed Dec 21, 2005 6:57 pm **Posts:** 70

b]Hibernate version:[/b] 3.1

Can Hibernate persist a subclass of a persistent class, where the subclass is not explicitly mapped or described to hibernate, but it's superclass is?

We are considering a proxying approach where we manually substitue "smart" subclasses of a persistent class when we send them to a remote (rich) client. When these "smart" subclasses come back, we would need them to be persistable.

Example:

Code:

class A {
  String foo;
  /* @hibernate.blah.blah */
  public String getFoo() {...}
  public void setFoo(String s) {...}
}

class SmartA extends A {
  String fooID;
  A underlyingObject = null;

  public String getFoo() {
     if (A==null)
         retrieveObjectFromServer(fooID)
     return A.getFoo();
  }
}

We want to replace A with SmartA to avoid sending the whole object graph to the client but if A is set on the client or modified, we want the saving, cascade-dirty checks to all work as normal.

Is this approach sound?

max · **Posted:** Mon Dec 26, 2005 1:06 pm

no - not very sound.

why not just only load the part of the objectgraph you actually want to send ?

damonf · **Joined:** Wed Dec 21, 2005 6:57 pm **Posts:** 70

Thanks for the help. One reason for our approach is caching.

If we bring back initial data for object X, and then need to get a bit more data X.getDetails() we'd rather extend the existing graph to include the details rather than re-retrieve X with Details. (Note we have a rich client application, so we have to incur significant overhead to go get a network of objects.)

Also, we can't figure out how to cache objects if we're going to have multiple copies retreived by different processes.