Re: JDO inheritance problem

[Ketan Gangatirkar]

Cédric,

You need to define the attribute persistent-capable-superclass in your 
.jdo file for the sub-class.  So if you have class A extends class B, 
your .jdo file would have:

<class name="B" persistence-capable-superclass="A">

The JDORI enhancer creates final methods to access the persistent 
attributes of the object.  If it does not know that B is a subclass of 
A, it will define them for both B and A, which will result in the error 
you see.  If A has an attribute z, then you should list it only in the 
<class> section of A.  Since B is a subclass of A, it will inherit the 
getter/setters that JDORI creates for z.  Only define B's unique 
attributes in the <class> section for B.  Like so:

<class name="A">
        <field name="z">
        <field name="y">
</class>
<class name="B" persistence-capable-superclass="A">
        <field name="x">
</class>


Cédric Pineau wrote:

 	Hello,

   I'm trying to use OJB through JDO and have a problem with basic
inheritance between two persitent class :
 I get "
     class entities.Statute2 overrides final method .
     java.lang.VerifyError: class entities.Statute2 overrides final
method .
        at java.lang.ClassLoader.defineClass0(Native Method)
        ... "
 at runtime when the classloader loads the Statute2 class.
 Statute2 inherits from Statute (this actually a test drive :-) Here is
my code :

Statute :
package entities;
public class Statute {
  protected int id;
  public int getId() {
    return this.id;
  }
  public void setId(int id) {
    this.id = id;
  }
                                                                        
                                                                     
  /** default constructor */
  public Statute() {}
  /** full constructor */
  public Statute(java.lang.String name) {
    this.name = name;
  }
                                                                        
                                                                     
  protected java.lang.String name;
  public java.lang.String getName() {
    return this.name;
  }
  public void setName(java.lang.String name) {
    this.name = name;
  }
                                                                        
                                                                     
  public String toString() {
    return "Statute "+this.name+" (id = "+this.id+")";
  }
}


Statute 2 :
package entities;
public class Statute2 extends Statute {
  /** default constructor */
  public Statute2() {}
  /** full constructor */
  public Statute2(java.lang.String name, String name2) {
    this.name = name;
    this.name2 = name2;
  }
                                                                        
                                                                     
  protected java.lang.String name2;
  public java.lang.String getName2() {
    return this.name2;
  }
  public void setName2(java.lang.String name2) {
    this.name2 = name2;
  }
                                                                     
  public String toString() {
    return "Statute "+this.name+" "+this.name2+" (id = "+this.id+")";
  }
}

repository_user.xml :
<class-descriptor class="entities.Statute" table="STATUTE">
  <extent-class class-ref="entities.Statute2" />
  <field-descriptor name="id" column="ID" jdbc-type="INTEGER"
primarykey="true" autoincrement="true"/>
  <field-descriptor name="name" column="NAME" jdbc-type="VARCHAR"/>
</class-descriptor>
                                                                        
                                                                     
<class-descriptor class="entities.Statute2" table="STATUTE2">
  <field-descriptor name="id" column="ID" jdbc-type="INTEGER"
primarykey="true" autoincrement="true"/>
  <field-descriptor name="name" column="NAME" jdbc-type="VARCHAR"/>
  <field-descriptor name="name2" column="NAME2" jdbc-type="VARCHAR"/>
</class-descriptor>

entities.jdo (partial) :
...
    <class name="Statute">
      <extension vendor-name="ojb" key="table" value="Statute"/>
      <field name="id">
        <extension vendor-name="ojb" key="column" value="id"/>
      </field>
      <field name="name">
        <extension vendor-name="ojb" key="column" value="name"/>
      </field>
    </class>
    <class name="Statute2">
      <extension vendor-name="ojb" key="table" value="Statute2"/>
      <field name="name2">
        <extension vendor-name="ojb" key="column" value="name2"/>
      </field>
    </class>
...
sql for table creation (postgresql) :
CREATE TABLE STATUTE (
  ID INT PRIMARY KEY,
  NAME TEXT
);
                                                                        
                                                                     
CREATE TABLE STATUTE2 (
  ID INT PRIMARY KEY,
  NAME TEXT,
  NAME2 TEXT
);

 I suppose I did something wrong but can't figure what. 
 I already tried to enhance only one of the two, to remove id and name
from Statute2 class-desciptor entry but...

 Can someone light my way to the wonderful world of JDO ?
 Thanks,
 Cédric





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