The main reason I support redirecting on-load is due to load failures.
So, if the user hits a page that displays data from a web service, and
the web method call fails because the server is not running, it can
return "webservicecallfailed" or something which would trigger a
navigation to a "/errorPage.xhtml" for example.
If the method handles the navigation in each method, there would be
similar code repeated throughout the application, which I am not a big
fan of.
I don't see it as a use for a 2nd level of navigation as it would
produce unnecessary overhead. The on-load component is also much more
simple to integrate and use and I put it out there for people who
didn't want to incorporate large frameworks into their JSF
application, but only wanted this small sub set of functionality.
With all that said, I really don't mind people using Shale instead and
many or most may choose to do so, I just wanted to provide another
solution that may be preferred by some people.
-Andrew
On 5/1/06, Craig McClanahan <[EMAIL PROTECTED]> wrote:
>
>
>
> On 5/1/06, Andrew Robinson <[EMAIL PROTECTED]> wrote:
> > As I mentioned, I didn't want to use Shale as it doesn't not have the
> > built-in ability to redirect from the methods (prerender for example),
> > at least not when I last looked.
>
>
> That (ability to redirect from *within* these event handling methods) is not
> built in, but it is possible to do manually. On the other hand, that also
> goes against the design patterns these methods are there to support -- the
> assumption is that someone, somewhere, already decided to navigate to this
> page, and did so either with a redirect or a forward, via either a GET or a
> POST. The prerender() method is all about what happens *next*, not how we
> got to this point.
>
> Think of prerender() as "set up the dynamic data I need to render the
> current page", not as "decide whether to display this page or go elsewhere".
> That should have been done already in your application's action method (for
> a POST), or via the hyperink or bookmark that got you here (for a GET).
>
> I'd be interested in exploring how your use cases might be different from
> the one ViewController is targeted at ... but perhaps that's a subject for
> the Struts list, since it is about the implementation of a Shale feature,
> rather than purely about JSF.
>
> > I was also afraid of
> > incompatibilities between Shale and JBoss-Seam.
>
>
> That shouldn't be a concern-- they will work together fine (although you'll
> probably be using Seam's notion of conversations rather than Shale Dialogs
> if you are using the combination).
>
> > -Andrew
>
>
> Craig
>
> > On 5/1/06, Craig McClanahan < [EMAIL PROTECTED]> wrote:
> > >
> > >
> > >
> > > On 5/1/06, Andrew Robinson <[EMAIL PROTECTED] > wrote:
> > > > I agree, I have not given up in trying to find a "built in" way of
> > > > doing it in JSF, but still have not found a way. The problem is that
> > > > JSF is all about actions when execution Java code. The problem is that
> > > > actions are never run on the first time a page is hit, only on POST
> > > > back. I guess it is simply a major gap when decoupling the business
> > > > code from the UI.
> > >
> > >
> > > This kind of issue was a key motivation for the ViewController
> functionality
> > > in Shale[1]. In particular, the prerender() method is a good place to
> deal
> > > with this kind of issue, because it:
> > >
> > > * Is called on both GET and POST requests.
> > >
> > > * Is called *before* rendering takes place, so you can
> > > effect the response (include error messages, etc.)
> > >
> > > * Allows you to set up resources that are required for
> > > rendering (allocate a JDBC connection, open a Hibernate
> > > session, whatever) that is required for rendering, then
> > > clean up after rendering in the destroy() method.
> > >
> > > You can do this kind of thing yourself with a phase listener, but you're
> > > going to end up basically replicating what Shale already provides.
> > >
> > > Craig
> > >
> > > [1] http://struts.apache.org/struts-shale/
> > >
> > >
> > >
> > > > I use the on-load component mostly for bookmarks. Say, somone
> > > > bookmarks "edit.jsf", I use the on-load component to redirect them
> > > > back to "index.jsf" if there is no property to edit (the backing bean
> > > > is not in an editing state).
> > > >
> > > > The other thing I use it for is to load data that may fail. Say
> > > > hitting a web service for example. In a getter method, the response is
> > > > probably already committed and therefore too late to redirect the user
> > > > or forward to a new page. Also, it is hard to add FacesMessages in a
> > > > getter as the message(s) component(s) may have already been rendered,
> > > > and once again it would be too late. The on-load allows me to
> > > > gracefully handle errors in backing-bean methods during the loading of
> > > > a new page.
> > > >
> > > > If there is a better way that you find or a way I can improve it, let
> > > > me know. I would have much preferred to see this in the specification
> > > > than have to make a one-off open source component.
> > > >
> > > > -Andrew
> > > >
> > > > On 4/30/06, benjamin van der veen <[EMAIL PROTECTED]> wrote:
> > > > > Andrew,
> > > > >
> > > > > Very informative message. Thanks a lot. I'm still a bit troubled by
> > > > > the fact that JSF didn't have this built in. It seems like such an
> > > > > integral piece of a web framework that is used to accomplish a wide
> > > > > range of tasks, so much so that it seems to me that the spec writers
> > > > > couldn't have simply forgotten it, and it makes me wonder if the
> tasks
> > > > > I would accomplish with it were accounted for somewhere else in the
> > > > > specification. Could you give me an example of what you use the
> onload
> > > > > method for? I know what I would do with it, but I'd just like to see
> > > > > what you have to say without trying to take into account what I
> write.
> > > > >
> > > > > Thanks,
> > > > > benjamin van der veen
> > > > >
> > > > > On 4/30/06, Andrew Robinson <[EMAIL PROTECTED] > wrote:
> > > > > > If you find any issues with the onload with jsf-comp please let me
> > > > > > know (I am the author). I am using it at home and at work without
> > > > > > issues except for JBoss-Seam EJB interceptors. Seam depends on the
> > > > > > action method unfortunately.
> > > > > >
> > > > > > I looked fairly closely at the spec before writing the onload and
> made
> > > > > > sure that the code I wrote conforms to what you are allowed to do.
> It
> > > > > > behaves similarly to an action that decides to forward/include a
> > > > > > non-JSF page. It uses the correct redirection and ensures the
> faces
> > > > > > response is marked complete. So in these respects, it should not
> > > > > > interfere with the specification at all. The only issue (like
> Seam) is
> > > > > > when code may not expect action methods to be executed outside of
> the
> > > > > > execute action JSF phase.
> > > > > >
> > > > > > I couldn't believe it either, before I wrote it, that JSF was
> missing
> > > > > > such a huge piece of functionality. All other languages (PHP,
> Perl,
> > > > > > ASP, ASP.NET, JSP) allow you to perform code when loading a page
> so I
> > > > > > don't know why it wouldn't be in JSF.
> > > > > >
> > > > > > As a side note, Shale has something similar with the page
> controller.
> > > > > > What I didn't like about it was that it had "void" as the return
> type
> > > > > > and therefore you could not as easily interact with the navigation
> > > > > > handling. The other problem I had with the JSF spec in these
> regards
> > > > > > was the lack of externalized functionality in the
> NavigationHandler
> > > > > > interface. I would love to get the view for a result without
> actually
> > > > > > navigating there, or be able to extend the navigation handler and
> be
> > > > > > able to modify the view after the method is fired but before the
> new
> > > > > > view is created.
> > > > > >
> > > > > > -Andrew
> > > > > >
> > > > > > On 4/30/06, benjamin van der veen < [EMAIL PROTECTED]> wrote:
> > > > > > > Xie Min,
> > > > > > >
> > > > > > > This is a great find, very close to what I'm talking about.
> However,
> > > > > > > in the following line:
> > > > > > >
> > > > > > >
> > >
> <to-view-id>/view.jsp?objectId=#{view.objectId}</to-view-id>
> > > > > > >
> > > > > > > what object does 'view' in the EL expression reference? Is this
> an
> > > > > > > implicit object, or one defined in a configuration somewhere? If
> it
> > > is
> > > > > > > implicit, how do I set it's properties from a backing bean?
> > > > > > >
> > > > > > > Thanks a lot,
> > > > > > > benjamin
> > > > > > >
> > > > > > >
> > > > > > > On 4/29/06, xie min < [EMAIL PROTECTED]> wrote:
> > > > > > > >
> > > > > > > >
> > > > > > > > in myfaces
> > > > > > > > wiki(
> > >
> http://wiki.apache.org/myfaces/Custom_Navigation_Handler),
> > > > > > > > threr are some suggestion on url parameters passing:
> > > > > > > >
> > > > > > > > Dynamic Url parameters passing: This allows passing parameters
> > > between pages
> > > > > > > > even when using redirection method. For exmaple, in order to
> > > navigate from a
> > > > > > > > pages name: view.jsp to a page named: edit.jsp, with the
> > > parameter:
> > > > > > > > objectId, the following thing can be done in navigation rule
> code:
> > > > > > > > <navigation-rule>
> > > > > > > > <from-view-id>/view.jsp</from-view-id>
> > > > > > > > <navigation-case>
> > > > > > > > <from-outcome>edit</from-outcome>
> > > > > > > >
> > > <to-view-id>/view.jsp?objectId=#{view.objectId
> }</to-view-id>
> > > > > > > > <redirect />
> > > > > > > > </navigation-case>
> > > > > > > > </navigation-rule>
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > 2006/4/30, benjamin van der veen < [EMAIL PROTECTED] >:
> > > > > > > > > I think that jsf-comp onload thing might be what I'm looking
> > > for. I
> > > > > > > > > really surprised that something like this isn't built in to
> JSF.
> > > Is
> > > > > > > > > using this extension violating some design principle
> fundamental
> > > to
> > > > > > > > > JSF?
> > > > > > > > >
> > > > > > > > > benjamin
> > > > > > > > >
> > > > > > > > > On 4/28/06, Andrew Robinson < [EMAIL PROTECTED]>
> > > wrote:
> > > > > > > > > > Have a look at:
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > >
> > >
> http://wiki.apache.org/myfaces/InvokingJsfPagesWithStandardUrls
> > > > > > > > > >
> > > > > > > >
> > >
> http://jsf-comp.sourceforge.net/components/onload/index.html
> > > > > > > > > >
> > > > > > > > > > -Andrew
> > > > > > > > > >
> > > > > > > > > > On 4/28/06, benjamin van der veen < [EMAIL PROTECTED]>
> > > wrote:
> > > > > > > > > > > Hello,
> > > > > > > > > > >
> > > > > > > > > > > I sent the message quoted below to this list a few days
> ago,
> > > but
> > > > > > > > > > > received no replies. I'm just wondering if perhaps it
> just
> > > got
> > > > > > > > > > > overlooked; I would appreciate any insight on this
> issue.
> > > > > > > > > > >
> > > > > > > > > > > Thanks a lot,
> > > > > > > > > > > benjamin
> > > > > > > > > > >
> > > > > > > > > > > On 4/26/06, benjamin van der veen <
> [EMAIL PROTECTED]>
> > > wrote:
> > > > > > > > > > > > Hello,
> > > > > > > > > > > >
> > > > > > > > > > > > I'm coming from a PHP background, and I've run into a
> wall
> > > with JSF.
> > > > > > > > I
> > > > > > > > > > > > know how I'd get around it with PHP or ASP.NET, but
> for
> > > JSF I'm
> > > > > > > > > > > > stumped.
> > > > > > > > > > > >
> > > > > > > > > > > > Here's the scenario:
> > > > > > > > > > > >
> > > > > > > > > > > > I'm making a message board. It has multiple forum each
> of
> > > which has
> > > > > > > > > > > > many topics, each of which has many posts. Very
> standard
> > > thing here.
> > > > > > > > I
> > > > > > > > > > > > am implementing the page which allows a user to create
> a
> > > new topic.
> > > > > > > > > > > > The URI is of the form "createTopic.jsf?forumId=<n>"
> where
> > > <n> is an
> > > > > > > > > > > > integer corresponding to the forum's primary key in
> the
> > > database. I
> > > > > > > > > > > > have a backing bean mapped in faces-config to
> > > "CreateTopicBean", and
> > > > > > > > > > > > it is request scoped. Now, when the user submits the
> form
> > > to create
> > > > > > > > a
> > > > > > > > > > > > topic, what is the best way to let the bean know which
> > > forum this
> > > > > > > > > > > > topic should be created under? I tried having a
> managed
> > > property
> > > > > > > > like
> > > > > > > > > > > > this:
> > > > > > > > > > > >
> > > > > > > > > > > > <managed-bean>
> > > > > > > > > > > >
> > > > > > > >
> > > <managed-bean-name>CreateTopicBean</managed-bean-name>
> > > > > > > > > > > > <managed-bean-class>
> > > > > > > > > > > >
> > > > > > > >
> com.wepwnsnails.faces.managedbean.CreateTopicBean
> > > > > > > > > > > > </managed-bean-class>
> > > > > > > > > > > >
> > > > > > > >
> <managed-bean-scope>request</managed-bean-scope>
> > > > > > > > > > > > <managed-property>
> > > > > > > > > > > >
> > > > > > > > <property-name>forumId</property-name>
> > > > > > > > > > > > <value>#{ param.forumId}</value>
> > > > > > > > > > > > </managed-property>
> > > > > > > > > > > > </managed-bean>
> > > > > > > > > > > >
> > > > > > > > > > > > but when the "action" attribute of the html <form>
> element
> > > rendered
> > > > > > > > by
> > > > > > > > > > > > JSF is simply " createTopic.jsf", so an EL exception
> is
> > > thrown when
> > > > > > > > JSF
> > > > > > > > > > > > fails to set the managed property.
> > > > > > > > > > > >
> > > > > > > > > > > > I've also tried adding a <h:inputHidden> tag set to
> the
> > > forumId on
> > > > > > > > the
> > > > > > > > > > > > backing bean in a variety of ways, but they leave much
> to
> > > be desired
> > > > > > > > > > > > as far as cleanliness.
> > > > > > > > > > > >
> > > > > > > > > > > > I'm sure that this is an issue every newbie JSF
> developer
> > > has
> > > > > > > > > > > > scratched his head over; so what's the best way to go
> > > about this?
> > > > > > > > I've
> > > > > > > > > > > > had a hard time finding anything in Google, mostly
> because
> > > I don't
> > > > > > > > > > > > know how to tersely phrase the problem for a seach
> query.
> > > > > > > > > > > >
> > > > > > > > > > > > Thanks a lot,
> > > > > > > > > > > > benjamin van der veen
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> > >
> >
>
>
