Werner Punz wrote:
Jonathan Harley schrieb:
Indeed. Because JPA is such a limited standard (only covers
relational datastores, for one thing),
Actually that is not quite true, JPA is not really limited
to relational datastores
Well, I suppose not but its query language is (yet another) dialect
of SQL and it uses SQL and relational terminology throughout its
annotations. It's clear what its designers had in mind.
JDO products as well as
Hibernate and Toplink will offer many extensions to the JPA standard.
Users will have a choice of using proprietary extensions (in the
case of Hibernate and Toplink) that lock them in to one vendor, or
standardised extensions (JDO) that give them a wide choice of vendor.
Exactly, but the point is, there are no key issues why you have to lock
yourself into it.
In the future it probably will be, that it is best to code against jpa
and use the extensions wisely, if needed (and in most cases it wont be
needed)
I disagree; I think it will be almost impossible not to use vendor
extensions. Take lazy loading, for example. JDO 2.0 defines exactly
which fields are available when an object is used while "detached"
from the store, and defines the exception which is thrown if client
code tries to access a different field. In Hibernate, whether access
succeeds depends on whether the field was already loaded, but a lazy
loading exception is thrown if not. In JPA, no particular behaviour
is defined, the spec merely observes that it might be "unsafe". If
you're using Hibernate JPA, no doubt you'll get the PROPRIETARY
Hibernate lazy loading exception, but using another vendor you
might just get null.
Maybe this discussion is wandering a bit far away from JSF. The
point I wanted to make is that if you like JSF because it's a
standard which gives you the choice to change vendor (and that's
certainly one of the things I use to persuade our clients that JSF
is good) then you should also look at standards for other areas
such as persistence. JPA is obviously worth a look, but right now
it's unfinished and seems to me quite poorly thought out.
Jon
--
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Dr Jonathan Harley .
. Email: [EMAIL PROTECTED]
Zac Parkplatz Ltd . Office Telephone: 024 7633 1375
www.parkplatz.net . Mobile: 079 4116 0423
