Question

I am developing an application using Hibernate and am trying to model the following scenario:

I have an Activity Abstract class, defined as follows:

@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="activityType")
@Table(name = "BF_ACTIVITY")
public abstract class Activity extends PersistableObject {

    @ManyToOne
    @JoinColumn(name = "ASSIGNED_TO")
    protected  Contactable assignedTo;

    @ManyToOne
    @JoinColumn(name = "RAISED_BY")
    protected  Contactable raisedBy;

Note I am using Single Table inheritance (so all implementing objects will use the same table) and have set a DiscriminatorColumn.

Now I have two objects that extend Activity: ToDo and Status:

@Entity
@Table(name = "BF_TODO")
@DiscriminatorValue("Todo")
public class ToDo extends Activity {
...


@Entity
@Table(name = "BF_STATUS")
@DiscriminatorValue("Status")
public class Status extends Activity {
...

Again note that for both implementations i have set a DiscriminatorValue.

Finally, I want to have a Person object, and the person can have a list of Status and a list of ToDo – I also want to capture the bi-directional relationship, so am modelling it using the mappedBy configuration, but in both cases using the “raisedBy” field that exists in the super class “Activity”:

public abstract class Person {

    @ManyToMany(mappedBy="raisedBy", targetEntity=Activity.class)
    private List<ToDo> todoItems = new ArrayList<ToDo>();

As i am using mappedBy with the member variable “raisedBy” from the super class I have also specified the targetEntity (otherwise it is not able to find the field in the ToDo object).

The problem is when I try to call getTodoItems() – it is actually just returning all “Activity” objects linked by “raisedBy” to the current person. e.g. it throws a cast exception because it is expecting the list of ToDos but Hibernate is returning Status objects in the list as well.

I was hoping the mappedBy config along with DiscriminatorValue would be enough to make this work – has anyone come across this or resolved it?

Thanks

---

EDIT

I have just found this post:

Can someone point me in the direction of a good @Where overview and example? could I just update my person as follows to use @Where with the discriminator column?

public abstract class Person {

    @ManyToMany(mappedBy="raisedBy", targetEntity=Activity.class)
    @Where(clause="activityType=Todo")
    private List<ToDo> todoItems = new ArrayList<ToDo>();

Answer 1

Add the annotation :
@Where(clause = “activityType= ‘Todo'”)

But it’s a hibernate annotation, not JPA