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So to try to flesh it out a bit more... I have an object let's call User and I want to know if that user is an employee or not. Employee's are their own object. So what I want to do rather than have an employee object is to have a boolean that tells me whether or not that User is an employee. I think this could be done with some form of readonly join?

Nate Spector
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  • A read only join? What does your database look like? Can you change it? (I.e., could you just add a boolean column to the user table) – Vala Jul 24 '12 at 12:24
  • no... i just want a boolean for if a row exists... basically i'm making up a column/variable based on whether or not a row exists. I am just saying that i'd assume it would be a read only join – Nate Spector Jul 24 '12 at 12:26
  • Can http://stackoverflow.com/a/2986354/692560 help you out? (Hibernate specific). – Vala Jul 24 '12 at 12:35

3 Answers3

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You can use a @JoinColumn to join the User object to an Employee object (you don't have to have more than the ID in it). You also don't need to have a getter for the Employee object, but you can now write an isEmployee() method that does the check employee != null. You probably want to make sure you use an eager fetch to always have the information there.

Vala
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JPA has a count functionality you can use in JPQL. You just have to make the distinction if it's an employee or not in your where clause.

Kurt Du Bois
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You can annotate getter method with @Transient and inside this method write logical operation, like if user_type is EMP then return true

Ramanqul Buzaubak
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