thanks pinaki, now i get it :)
i must say though that these are confusing semantics. JPA wants me to name the
fields and mutators the same between the Page and PageId class, but for them to
be different types. imagine an object model with two classes and two methods,
Foo.getBlah()
Bar.getBlah()
where Foo.getBlah() returns a String, and Bar.getBlah() returns an int. not
exactly intuitive to the user of such an API.
anyway :)
Pinaki Poddar <[EMAIL PROTECTED]> wrote: Page can have a primary key field type
of "Book".
@IdClass(com.mycompany.book.PageId.class)
@Entity
public class Page {
@Id
int number;
@Id
@ManyToOne
private Book book;
}
public class PageId {
int number;
String book; // the type "String" must match the type of primary key
used in Book.java
// the name of the variable "book" must match
the name of the variable in Page class.
}
public class Book {
@Id
String title;
}
Pinaki Poddar
BEA Systems
415.402.7317
-----Original Message-----
From: jeff [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 28, 2007 4:35 PM
To: open-jpa-dev@incubator.apache.org
Subject: RE: composite ID based on "one" side of a bidirectional
one-many relationship
hi,
abe closed this with the reasoning ...
"the book field in the PageId class must be of type String to match the
primary key field type of Book"
was i mistaken when i understood you to say that Page could have a PK
field of type Book? if not, very sorry for all the confusion.
or were you just saying that open JPA allowed the PK field to be a
ManyToOne relationship?
p.s., it's issue #191
https://issues.apache.org/jira/browse/OPENJPA-191
Patrick Linskey
wrote: Yes, please do. It looks like
your code should work.
-Patrick
--
Patrick Linskey
BEA Systems, Inc.
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> -----Original Message-----
> From: jeff [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, March 28, 2007 10:31 AM
> To: open-jpa-dev@incubator.apache.org
> Subject: RE: composite ID based on "one" side of a bidirectional
> one-many relationship
>
> yes, i see the problem w/ the attached classes, and with a completely
> different model where i am trying to accomplish the same thing.
>
> should i file a bug? i can attach the test case there.
>
> Patrick Linskey
wrote: Are you still
> seeing that same problem with the code that you attached?
>
> -Patrick
>
> --
> Patrick Linskey
> BEA Systems, Inc.
>
> ______________________________________________________________
> _________
> Notice: This email message, together with any attachments, may
> contain information of BEA Systems, Inc., its subsidiaries and
> affiliated entities, that may be confidential, proprietary,
> copyrighted and/or legally privileged, and is intended solely for the
> use of the individual or entity named in this message. If you are not
> the intended recipient, and have received this message in error,
> please immediately return this by email and then delete it.
>
> > -----Original Message-----
> > From: jeff [mailto:[EMAIL PROTECTED]
> > Sent: Tuesday, March 27, 2007 1:42 PM
> > To: open-jpa-dev@incubator.apache.org
> > Subject: RE: composite ID based on "one" side of a bidirectional
> > one-many relationship
> >
> > Patrick Linskey
> wrote:
> >
> > > my ID class has a book field, and getters and setters for it >
> > to match Page's book field. i wonder about the last line > where it
> > says "java.lang.String". that seems odd.
> >
> > Can you post your Book and Page classes and the Page's IdClass?
> >
> >
> > attached. i keep trying to attach the entire project as a zip, but
> > apache's spam filter keeps dropping it. let me know i could send to
> > you directly.
> >
> >
> > > so, regardless, even if that did work, correct me if i am >
> > wrong, but it'd be a really bad idea to depend on openjpa >
> > specifics, because my app doesn't get to choose the JPA >
> > implementation, it has to use whatever the java ee container >
> > gives it ... right?
> >
> > No -- a Java EE 5 container *must* allow you to specify your
> > persistence provider. Whatever you put in the element in the
> > persistence.xml must be obeyed. Only if you do not specify a
> > element can the implementation can choose whatever it wants to use.
> >
> >
> > yes, duh. sorry.
> >
> >
> >
> > Correct.
> >
> > > so, assuming i do need to accomplish this, is there a best >
> > practice? as i mentioned, what i did to make it work was make > the
> > Page's composite ID incorporate the Book's ID by adding a >
> > "derived" bookName field to Page, like ...
> >
> > You could add a private bookName field that has no external
> > mutators or accessors, and create a @PreStore callback that copies
> > the value from the related Book into the field. That would do a
> > decent job of isolating the artifact from the rest of your app.
> >
> >
> > yes, that works.
> >
> > ________________________________
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