User's Vases Hibernate Problem

[Ram Gole]

The situation is Users have Vases. But the vases maybe broken.

The tables look like this

|---------------|                 |-------------|
| Vase          |                 |  User       |
|---------------|                 |-------------|
|long *id       |                 |long *id     |
|boolean broken |                 |String name  |
|User owner     |*---------------1|             |
|---------------|                 |-------------|

The mappings look like this

class Vase {
  private long id;
  private User owner;
  private boolean broken;
  
  /*  Snip getters and setters   */
}
 
class User {
  private long id;
  private String name;
  private Set<Vase> vases;
  
  /*  Snip getters and setters */
}
 
<class name="User" table="Users">
    <id name="id" column="USER_ID" type="long">
        <generator class="native"/>
    </id>
    <property name="name" column="USER_NAME"
           type="string" not-null="true"/>
    <set name="vases" inverse="true" cascade="save-update">
        <key column="OWNER"/>
        <one-to-many class="Vase"/>
    </set>
</class>

But I need to have methods getBrokenVases() and getGoodVases() in the User class. Also for these calls I don't want all Vases come to the web server from the DB but only broken or good ones (for performance reasons). What approach should I take.

Approach 1 : I could think of is I should have two Sets in class User and use a "where" attribute of mapping <set>. But is it true that in "where" attribute I can only put in native sql. How do I use HSQL ?

Approach 2 : Use filters. This seems like a new approach. But here too can I only use native sql.

One other problem I faced was the generated SQL won't execute because in the where clause I used table names. But else where Hibernate used aliases. So the query wouldn't run unless I use alias in where clause. So how do I know what alias Hibernate generates? Is this only a problem with Derby db.

Please suggest a good solution to this problem. I would prefer to use HSQL.

[Mark Spritzler]

What about inheritance, create subclasses of Vase, and then use the boolean as the discrimintor value. I will let you find out how to do that on your own, as this is a coursework homework that you are doing. Good Luck. Your thoughts aren't off either, but I think inheritence is the easiest, once you get past the terms.

Mark