persistence@glassfish.java.net

RE: using composition with JPA

From: sud <to_sud_at_yahoo.com>
Date: Tue, 24 Jul 2007 07:27:04 -0700 (PDT)

I'm still unclear about the solutions proposed. Here's a more detailed real-life explanation of what I'm trying to achieve and I'd any appreciate help figuring this out. I have a JPA entity class called Vehicle as below @Entity public class Vehicle { @Id private int VIN; private String model; private String color; ..... ..... } I have a second JPA entity class called Permit which represents vehicle permits issued by the agency @Entity public class Permit { @Id private int number; private Date issuedDate; private Vehicle vehicle; .... .... } My business rule is a Vehicle can have many permits issued to it and a Permit can be issued to one and only one Vehicle. You should always be able to retrieve a specific permit and say what was the vehicle it was issued to. So if a permit was issued to a vehicle with color Red, and if the same vehicle has since been updated to color Blue, the permit that was issued should still say vehicle color Red. This is what I meant by the Permit is composed of Vehicle and that the instance variable vehicle in Permit is a snapshot of a vehicle when that permit is created. All this leads mean to believe that I need to be able to store the values of the Vehicle object in the Permit table and not create a reference from the Permit table to the Vehicle table. That way if the vehicle was updated, the permit still has the original properties of vehicle it was issued to. I hope I explained myself better now. Please let me know how to go about this in JPA. -sud My issue is with the vehicle object in the Permit class. If ____________________________________________________________________________________ Got a little couch potato? Check out fun summer activities for kids. http://search.yahoo.com/search?fr=oni_on_mail&p=summer+activities+for+kids&cs=bz