I don't think we all agree about Spring's role in Wicket. It's fine to
say that Spring will open and close Hibernate transactions if you want
to use it, but that's not a good reason to delete projects that do the
same thing without Spring.
Nathan
Igor Vaynberg wrote:
> irt spring+hibernate+wicket:
>
> Dan is absolutely correct when he says that wicket should never touch
> hibernate directly. all the hibernate-related logic should stay inside
> spring and be exposed directly through a dao object or through a
service
> facade. i think wicket-contrib-data and wicket-contrib-data-hibernate
> should be taken out of cvs as they do not display good programming
> practices in general. i thought Phil was going to do that, but i guess
> he never got around to it, are you reading Phil?
>
> take a look at wicket-phonebook in wicket-stuff, its an extremely
simple
> crud application that uses the above technologies. it also has
excellent
> javadoc thanks to Gwyn.
>
> irt general dao:
> if you are talking about pulling out data from the database to
display,
> such dao already exists and is documented. look up: IDataProvider in
> wicket-extensions. it is used by the DataView component which is also
in
> the extensions. to see a demo of these look in wicket-phonebook or
> wicket-examples - repeaters. the repeater examples build upon each
other
> from a simple looping view to a fully database driven datatable
component.
>
> irt spring integration:
> spring integration doesn't come easy with a framework like wicket.
> unlike servlets which are fairly static singletons wicket applications
> consist of a lot of volatile objects with varying life cycles. this
> makes keeping dependencies difficult especially because objects are
> often serialized. there are basically two approaches: simpler approach
> is to keep all your dependencies in wicket's singleton Application
> object and let everything else look up dependencies from there, the
> other approach is more sophisticated - it involves creating proxies
for
> dependencies that can be serialized and retain enough information to
be
> able to look up the dependency when they are deserialized (possibly in
> another vm). i recently wrote up an article on this in the wiki that
> describes the two ways:
> http://www.wicket-wiki.org.uk/wiki/index.php/Spring i haven't had much
> time to spend on it so its rough around the edges. people should feel
> free to fix it, it is a wiki after all.
>
> irt detaching:
> the whole idea of detaching objects is to reduce session state. if you
> have a pretty big object that you are using as a model, why keep it in
> session when you can only keep the id and load the object when it is
> fist accessed. if you are using the object as a model for the form,
then
> you don't need to reattach/lock it, just use hibernate merge instead
of
> saveorupdate. see wicket-phonebook for both use cases.
>
> irt trail tutorial:
> if someone can come up with a scope/spec for a small
> wicket+hibernate+spring application / trail breakdown i can put one
> together as long as other people promise to write documentation, some
> javadoc, and dress up the html templates.
>
> -Igor
>
>
> On 11/17/05, *Dan Gould* <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
wrote:
>
> Sam Gendler wrote:
> ...
> > The nice thing is that if
> > examples use a fairly generic DAO abstraction, it should be possible
> > to provide nice examples that aren't dependant upon any particular
> > suite of technologies. Just describe the DAO interface and then use
> > those them to access standard POJOs. Obviously, most folks will
> > probably be doing a Hibernate/Spring thing, so addressing best
> > practices for combin ing those technologies with Wicket is
> enormously
> > valuable, but it should be secondary to providing generic best
> > practices for dealing with DAO access, detachability, etc.
> ...
> > 1. hibernate/spring integration (separate from wicket)
> > 2. hibernate/spring/wicket best practices
>
> Sam -- all of what you propose sounds excellent.
>
> [The tradional example has been the pet shop, but nowadays, I think a
> blogging system is a nice worked example for a web framework.]
>
> I haven't had a chance to look at Igor, et al's new Spring
integration,
> but here are a few bits of advice from my experiments with
> Wicket/Spring/Hibernate:
>
> - If you're using Spring to manage your DAOs, you don't need to look
at
> wicket-contrib-hibernate.
>
> - Spring and Hiberate already integrate together really easily. Take a
> look at
> org.springframework.orm.hibernate3.LocalSessionFactoryBean. They
> should have plenty of examples, but if you need a more complete
> spring.xml, let me know and I'll send you one.
>
> - To map Hibernate sessions to requests, Spring AOP's
> OpenSessionInViewInterceptor makes everything automatic. Here's what I
> use:
>
> <!-- The openSessionInViewInterceptor is for Wicket
> requests; the HibernateInterceptor
> is for business objects -->
> <bean name="openSessionInViewInterceptor"
>
> class="
org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor
> ">
> <property name="sessionFactory"><ref
> bean="sessionFactory"/></property>
> <property
> name="flushModeName"><value>FLUSH_AUTO</value></property>
> </bean>
>
> - For an example of Transaction Templates, take a look at
>
>
http://blog.exis.com/colin/archives/2004/07/31/concise-transaction-definitions-spring-11/
>
> - If you can get to the DAOs from your pages or models and your
Sessions
> are managed correctly, using them with Wicket is very easy.
>
> - I'm not yet sure what the best practice for detatching is. If you
> have
> relatively small objects and plety of RAM, you could use hibernate's
> lock() function to attach to the current Hibernate session. Most
> likely,
> though, having your models keep the id of the object and loading
> them from the
> DAO maks the most sense.
>
> Good luck,
> Dan
>
>
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