How to get the DiscriminatorValue at run time

Question

We have the following classes

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) // optional annotation as this is default
@DiscriminatorColumn(name = "apType", discriminatorType = DiscriminatorType.STRING, length = 255)
@DiscriminatorValue("AP")
public class ApplicationProcess {
}

And this

@Entity
@DiscriminatorValue("APS")
public class ApplicationProcessScheme extends ApplicationProcess {
}

Now I need to know at runtime if the ApplicationProcess is of DiscriminatorValue AP or APS. Since this is automatically handled by jpa, I have no way of getting this value.

We are calling a method that takes an ApplicationProcess as parameter, and I want to avoid using instanceof to check what type it is. Would be cooler if I could do something like

applicationProcess.getApType().equals("AP");

Answer 1

We are calling a method that takes an ApplicationProcess as parameter, and I want to avoid using instanceof to check what type it is. Would be cooler if I could do something like (...)

I don't think it would be cooler, this seems worse than calling instanceOf to me: if for whatever reason you change the discriminator value, it would break your code.

If you need to check the type, use instanceOf. A trick using the discriminator is not going to make things nicer, it would just make your code less robust.

Answer 2

You can map your discriminator as a read-only property:

public class ApplicationProcess { 

    @Column(name = "apType", insertable = false, updateable = false)
    private String apType;

    ...
}