Does there exist an example (vlib or similar) of a page that only gets
information from database on render, and that uses a custom datasqueezer and
no db fetching for the rewind phase? My ideal design is that all known
information in the rewind phase comes from request parameters, that way many
synchronization issues can be avoided (request not matching content from
database or other state).
Inge
On 2/16/06, Inge Solvoll <[EMAIL PROTECTED]> wrote:
>
> Yes, items is always null in pageBeginRender. If I remove the else clause,
> it is also null in the form listener. The else clause just prevents null
> values before render.
>
> I actually expect the values to be null in pageBeginRender, but I expect
> the collection to be populated in the end of the rewind, in the form
> listener...
>
> Inge
>
> On 2/16/06, Ryan <[EMAIL PROTECTED]> wrote:
> >
> > It appears your problem is that getItems() will always be null in
> > pageBeginRender because at that point parameters have not been bound.
> > Try removing that else clause.
> >
> > Ryan
> >
> > On 2/16/06, Inge Solvoll < [EMAIL PROTECTED]> wrote:
> > > I guess my (first) problem is simpler than this discussion, I'll try
> > to
> > > explain:
> > >
> > > When I submit my form, I expect my page properties to be updated
> > during
> > > rewind automatically, without me having to write any java code to make
> > that
> > > happen. But so far I haven't understood how this happens. I include
> > here a
> > > simple code example that I think illustrates my problem quite well.
> > Why is
> > > my collection always empty when the form listener is reached? If I run
> > the
> > > initItems() method on both rewind and render, the values from the
> > request
> > > parameters are written into the page properties.
> > >
> > > My ultimate question is: Do I really have to get the items list from
> > the
> > > database during rewind? Isn't there a way to avoid this, making
> > tapestry
> > > automatically build the items collection from the request parameters?
> > As I
> > > wrote in another similar post on the list about DataSqueezer, I've
> > tried
> > > creating a datasqueezer for this, but the collection is still showing
> > up
> > > empty.
> > >
> > > My HTML file:
> > >
> > >
> > --------------------------------------------------------------------------
> > >
> > > <body jwcid="@Body">
> > >
> > > <form jwcid="@Form" listener="listener:formListener">
> > >
> > > <span jwcid="@For" source="ognl:items" value="ognl:currentItem">
> > > <span jwcid="@Insert" value="ognl:currentItem.name"/><br>
> > > <input type="text" jwcid="@TextField" value="ognl:
> > currentItem.name"/>
> > > <br>
> > > </span>
> > >
> > > <input type="button" jwcid="@Submit" value="Submit form now"/>
> > >
> > > </form>
> > > </body>
> > >
> > > -------------------------------------------------------------
> > >
> > > <page-specification class="Test">
> > > <property name="items"/>
> > > <property name="currentItem"/>
> > > </page-specification>
> > >
> > > -------------------------------------------------------------
> > >
> > >
> > > public abstract class Test extends BasePage implements
> > > PageBeginRenderListener {
> > >
> > > static Log log = LogFactory.getLog(Test.class);
> > >
> > > public abstract Collection getItems();
> > > public abstract void setItems(Collection c);
> > >
> > > public void pageBeginRender(PageEvent event) {
> > >
> > > if (!getRequestCycle().isRewinding()) {
> > > initItems();
> > > }
> > > else {
> > > if (getItems() == null) {
> > > setItems(new Vector());
> > > }
> > > }
> > > }
> > >
> > > public void formListener(IRequestCycle cycle) {
> > > Collection items = getItems();
> > > for (Iterator iter = items.iterator(); iter.hasNext();) {
> > > Item currItem = (Item) iter.next();
> > > log.debug("Current item id: " + currItem.getId() + ", name: " +
> > > currItem.getName());
> > > }
> > > }
> > >
> > > private void initItems() {
> > > Collection items = new Vector();
> > >
> > > items.add(new Item(new Long(1), "Item 1"));
> > > items.add(new Item(new Long(2), "Item 2"));
> > >
> > > setItems(items);
> > > }
> > > }
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > On 2/15/06, Ryan <[EMAIL PROTECTED]> wrote:
> > > >
> > > > You may want to look at the method prepareForRender(). This is the
> > > > method that handles binding of properties to form values. It is also
> > > > called just before the component is rendered and in the order in
> > which
> > > > they are rendered on the page (where pageBeginRender is called
> > before
> > > > anything renders and is called in an undefined order). Also note
> > that
> > > > prepareForRender is not called if the component is not rendered (for
> > > > instance if it is in an @Conditional that evaluates to false).
> > > >
> > > > I have received the best results from using pageBeginRender for
> > > > initializing page properties that are static (ie known at all times
> > > > during render, for instance a property select model property) and
> > > > using prepareForRender in other times.
> > > >
> > > > Ryan
> > > >
> > > > On 2/14/06, Inge Solvoll <[EMAIL PROTECTED]> wrote:
> > > > > I would like to provoke some debate on whether this is a good
> > design
> > > > pattern
> > > > > or not:
> > > > >
> > > > > public void pageBeginRender(PageEvent event) {
> > > > > initState();
> > > > > readItemsFromDatabase();
> > > > > }
> > > > >
> > > > > private Collection readItemsFromDatabase() {
> > > > > return getDatabaseConnection().getItems();
> > > > > }
> > > > >
> > > > > private void initState() {
> > > > > // Init all crucial page state here
> > > > > }
> > > > >
> > > > > My problem is that some ids in hidden inputs are needed by the
> > initState
> > > > > method. These values are not available in the pageBeginRender
> > method
> > > > during
> > > > > rewind, because the Hidden components containing them haven't been
> > > > rendered
> > > > > yet. I need this state information on a per-request basis, not
> > > > per-session,
> > > > > so it is not possible to persist the page property. So far, I'm
> > solving
> > > > this
> > > > > by using good-old request parameters, and reading them the old
> > servlet
> > > > way
> > > > > in the pageBeginRender method like this:
> > > > >
> > > > > String crucialId = getRequest().getParameter("crucialId");
> > > > > page.setCrucialId(new Long(crucialId));
> > > > >
> > > > > I generally run into a lot of problems trying to find a good
> > pattern for
> > > > > setting up data to fit with the RequestCycle. I have ended up
> > doing the
> > > > > database reading in the pageBeginRender method, meaning that my
> > data for
> > > > the
> > > > > page is being read on every single rewind and render. I find it a
> > bit
> > > > hard
> > > > > to understand how to achieve this:
> > > > >
> > > > > On render:
> > > > > - Read data from database and set page properties
> > > > >
> > > > > On rewind:
> > > > > - Create non-null, empty, page properties ready to be populated
> > from the
> > > > > request.
> > > > >
> > > > > My rewind step here often fails, and I don't see why. My page
> > properties
> > > > > don't seem to be populated, when I leave them as, say, a non-null
> > empty
> > > > > java.util.Collection to be populated with items from the request.
> > > > >
> > > > > Long and not very concentrated post, I actually don't know where
> > to
> > > > start
> > > > > here :)
> > > > >
> > > > > Inge
> > > > >
> > > > >
> > > >
> > > >
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> > > >
> > >
> > >
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>
