Question

I’m new to JDO specification and Datanucleus implementations and i’m struggling right now in my Project with the error described above.

What steps will reproduce the Problem:

1- Defining a Class “DefaultDiffTask”:

`@PersistenceCapable
public class DefaultDiffTask implements IDiffTask, Serializable {
@Persistent
protected IDiffTaskTarget diffTaskTarget;
@Persistent
protected String diffTaskId;

protected IDiffTaskPhasesMgr diffTaskPhasesMgr;

@Persistent
protected IDiffTaskType diffTaskType;

@Persistent
protected String taskCreationTime;

public DefaultDiffTask() {

this.diffTaskTarget = new DefaultDiffTaskTarget(
    new DefaultPageStateLocation(""), new DefaultPageStateLocation(
        ""));
this.diffTaskPhasesMgr = new DefaultDiffTaskPhasesMgr(this); //
DiffTaskUtility.createTaskPhasesMgr(this);
this.diffTaskType = new DefaultDiffTaskType(
    DiffTaskTypeEnum.CRAWLER_BASED_DIFF);
this.taskCreationTime = (new Date()).toString();
this.diffTaskId = this.generateDiffTaskId();

}

public DefaultDiffTask(IDiffTaskTarget diffTaskArea,
    IDiffTaskType diffTaskType) {
this.diffTaskTarget = diffTaskArea;
this.diffTaskPhasesMgr = new DefaultDiffTaskPhasesMgr(this); // DiffTaskUtility.createTaskPhasesMgr(this);
this.diffTaskType = diffTaskType;
this.taskCreationTime = (new Date()).toString();
this.diffTaskId = this.generateDiffTaskId();
}
...........`    

2- try to retrieve some previously stored object with :

PersistenceManagerFactory pmf = JDOHelper
    .getPersistenceManagerFactory(.....);
// Persistence of a Product and a Book.
PersistenceManager pm = pmf.getPersistenceManager();
Transaction tx = pm.currentTransaction();
try {
    tx.begin();
    System.out.println("Retrieving Extent for Default");
    Extent e = pm.getExtent(DefaultDiffTask.class, true);
    Iterator iter = e.iterator();
    while (iter.hasNext()) {
    Object obj = iter.next();
    System.out.println(">  "
        + ((DefaultDiffTask) obj).getDiffTaskId());
    }
    tx.commit();
} catch (Exception e) {
    System.out.println("Exception thrown during retrieval of Extent : "
        + e.getMessage());
} finally {
    if (tx.isActive())
    tx.rollback();
    pm.close();
}

the expected output:

Retrieving Extent for Default:
something here

But i get he following exception:

Retrieving Extent for Default
Exception thrown during retrieval of Extent : Field "net.she.sw.diff2w3c.diff.tsk.DefaultDiffTask.diffTaskTarget" is declared as a reference type (interface/Object) but **no implementation classes** of "net.she.sw.diff2w3c.diff.tsk.target.IDiffTaskTarget" have been found!


my point is, i have some implementation of the interface net.she.sw.diff2w3c.diff.tsk.DefaultDiffTask.diffTaskTarget which have the annotation “@PersistenceCapable” like:

@PersistenceCapable
public class DefaultDiffTaskTarget extends AbstractDiffTaskTarget {
public DefaultDiffTaskTarget(IDiffTaskTargetStateLocation firstLocation,
    IDiffTaskTargetStateLocation secondLocation) {
super(firstLocation, secondLocation);
// TODO Auto-generated constructor stub
}

or

@PersistenceCapable
public class DefaultDiffTaskTarget extends AbstractDiffTaskTarget {

or

@PersistenceCapable
public class PageAreaTarget extends AbstractDiffTaskTarget {

this object are injected in the constructors (default and custom) when a DefaulfDiffTask get created…

so my point is

• Why this error ?
• is it something i am missing ?
• all the implementation of the implementations of the interface IDiffTaskTargetare present in the classpath AND have the Annotations for the JDO/Datanucleus to work

i know the problem is on my code and not on the side of JDO/Datanucleus,
and i will be greatful for any given help

Answer 1

How does DataNucleus know of your other classes ? you expect it to guess where they are ? Why not just specify them as per the docs http://www.datanucleus.org/products/accessplatform/jdo/orm/interfaces.html