-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 There's actually no way - at least according to the documentation, my own experience, and Google - to specify an unsaved-value using just annotations. You'd have to use a mapping file for this. But apart from that, Jonathan is spot on. :)
/Filip On 2009-02-10 12:16, Jonathan O'Connor wrote: > Uli, > Using Object for key fields is a standard micro pattern in JPA and > Hibernate. Of course, the DB does not want to save null as a key field > value, but the most people get the entity manager to auto-generate keys > for their objects. > > By leaving the key as null, the entity manager knows that it needs to > persist the object, generating a key for it. This is a handy pattern, > when you want to create a parent object with several children, and then > persist the whole object tree in one call (otherwise, you would have to > persist the tree, one object at a time, from the bottom up - Yikes!). > JPA/Hibernate can only do this if it knows what a null key value is, and > in Java that is of course, null. I think (from memory) you can define a > specific value as a null, so you could use an int or a long as a key > field type, and then specify, for example, -999, as the null value. > Then, you have to set the key field to -999 somewhere, and this is all > too much work for most people, therefore, they use Object key field values! > > Ciao, > Jonathan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iQEcBAEBAgAGBQJJkd4/AAoJEEfiH7PpjaMnoDwH/1SdtbIjF0uqxbqe8GJONrty cYM5Y9Nyh7KTVrNCHaFd0me6TgTYUpjvZnwzIufIZmIA/pp05PcmhpoN2DLXbT/o 6Ixx+yFDQdO0RX2D7fUEk+Gtpl55pvZ63UMWNPbGZcqU1FOLaie6s1Qm9p0NYCmN BcrXRtKDfkaJUN/ayKflukK3UAtkdpW25R183JsEOzncBkBB3XynTYQk0oWXcTEF kmVz8+Ki9y+ZBPPDp/M+P+IkTK+DNw979uAUiaxHtPb0eueew9D365ewUpstKuxt 95K28mlpkKxwbQYXUHAC5buNJzMdro4bspGZ+UPwbUAg3vJ1WagLKuJYhCEytv8= =jyxQ -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tapestry.apache.org For additional commands, e-mail: users-h...@tapestry.apache.org
