On 11/29/06, Simon Kitching <[EMAIL PROTECTED]> wrote:
Craig McClanahan wrote: > > > On 11/29/06, *Naresh Bhatia* <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > Hi Simon, > > Thanks for a quick response. > > When I said "navigates through a link", I had first tried h:commandLink. > However, as you mention below, it was posting back to page A and causing > an unnecessary database read (I was doing lazy loading in my bean and > since this was a brand new bean, it was hitting the DB for no good > reason). > > > FWIW, this is the kind of use case that Shale[1] tries to solve with the > view controller paradigm. The idea is that you put logic like this > database lookup into the prerender() method of the backing bean, which > will only be called if *this* is the view that will be rendered, not if > you navigated to somewhere else instead. > > Craig > > [1] http://shale.apache.org/ Is what you describe what Naresh really wants? I though he simply wants a link on the page that navigates to another page without any logic being processed on the backing bean for the current page. Shale's view controller can be very useful, and can certainly be used as you describe to avoid performing database access until the render phase, but that's not quite the same thing.
WIthout seeing the actual code its impossible to know for sure, but I've seen *lots* of people do database lookups like this in the constructor of their backing beans, where it's going to get executed whether you need it (because you are going to redisplay the current page) or not (because you are going to navigate somewhere else instead). I read into his comment about the wasted database access that he was doing something like this -- which gets bypassed when you use hyperlinks (or <h:outputLink> to navigate between pages, instead of something like <h:commandLink> which submits the form (and therefore goes through the JSF lifecycle) on the current page. The view controller solution still executes "logic" on the submitted-to page ... the trick is to only execute the database query when you need it. And, it solves his other complaint, of keeping the navigation logic centralized in the navigation rules configuration, rather than being spread out across all the pages. Regards,
Simon
