Gracefully handling 404s with Lift
February 21st, 2010
In my continuing effort to improve the wider knowledge of Lift, here’s another great nugget that shows you how to provide a 404 handler powered from a Lift template
class Boot {
def boot {
// ...other stuff...
LiftRules.uriNotFound.prepend(NamedPF("404handler"){
case (req,failure) =>
NotFoundAsTemplate(ParsePath(List("404"),"html",false,false))
})
}
}
And I have a 404.html file in the ./webapp/404.html with the contents:
<lift:surround with="default" at="content">
<h2>Ooops!</h2>
<p>Wow, we totally couldn't find your page. Sorry about that.</p>
</lift:surround>
Then whenever a user browses to a URL that is not supported by your application, you can give them a friendly (and nicely designed) webpage rather than some technical message about 404s.
Note: The only cavet is not to use the <lift:menu /> snippet within your 404 template because Lift is unable to calculate the SiteMap when its a URL that is not accounted for within that scheme.
UPDATE The above note is now redundant because of commit by Marius on issue 376
Using Jetty 7 continuations to power Lift comet support
February 18th, 2010
Recently, Marius added an abstraction layer within Lift so that we could support different comet implementations over different servlet containers. Out of the box, we provide two both Jetty 6 and Jetty 7 APIs. This API is however not very well documented so I thought I would just write a short post on how to use it. In your Boot.scala file you need to put something like:
import net.liftweb.http._
import provider.servlet.containers.Jetty7AsyncProvider
class Boot {
def boot {
// ...other stuff here...
LiftRules.servletAsyncProvider = (req) =>
new Jetty7AsyncProvider(req)
}
}
Thats pretty much all you need to do in order to swap comet implementations! If you want to use something else, like Resin etc, all you need to is write the correct provider and away you go.