Re: T5: Custom components are not statefull

Wed, 06 Feb 2008 00:42:46 -0800 

Hello,
Indeed, the graph (my component) works fine outside of a loop when I have several of them on a page. The data to display (in that case a TimeSeries for a JFreeChart) is kept in the instance of the component so when the page display, the src value refers to the correct graph and data. 


My problem is indeed in Loops. Why can't I "force" Tapestry to create  
a new instance of my component for each Loop iteration. Then I could  
have a different src value for each graph in my Loop and it would  
"just work". I was using WebObjects several years ago and that's how  
it was working.



At worse, it would be nice to have an option to allow this behavior.  
Otherwise, as you say, I need to keep the data outside of the  
component and put it in the page. This means my component is not truly  
independent and I need to put some kind of logic in the page. Less  
good in my opinion because less "self contained".


Alex

Le 5 févr. 08 à 21:19, Josh Canfield a écrit :


Hi Alex,



Actually, the component itself now generates a new id correctly  
(using

the solution that was suggested).




Your component actually hasn't gotten a new id, you've just  
generated a
unique id based on your component's id. This is a good thing because  
if you
had several images that you were generating in a single rendering of  
your
component, you might want to generate several unique ids to refer to  
those

images (perhaps an independent legend image?). You wouldn't want a new
instance of your component created every time you created a unique id,
right?


Since you want to generate the charted data in the page request, and  
not the
image request, you need to store that data somehow. It sounds like  
you were
hoping that Tapestry would automatically know what data you wanted  
stored
per rendering of your component, as opposed to per instance as it  
works now.
Since the loop doesn't actually create a new instance of your  
compenent for
every iteration, you are going to have to make your component  
understand
what it means to be rendered in a loop. This most likely means  
storing the
data in a map during the page render request so that the data can be  
pulled
back out of the map during the image render request. You can persist  
this
map in the component using @Persist. It's not ApplicationState, it's  
page
state and it sounds like you do want your chart rendering to depend  
on page

state.


Doing things this way makes your image links require a page render  
before
they will work. If you want to allow people to pass around links to  
the
images then they'll fail outside of the page because the data won't  
be there

to recreate them.

Josh


On Feb 5, 2008 3:39 AM, Alexander Lamb  
<[EMAIL PROTECTED]> wrote:



Actually, the component itself now generates a new id correctly  
(using

the solution that was suggested).

As you can see in the HTML generated:

<div><img id="toto_1" onclick="window.open('./
statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/
920/560','_blank','width=944, height=584')" src="./
statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/460/280"
style="cursor:pointer"><div></div></div><br>
<div><img id="toto_2" onclick="window.open('./
statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/
920/560','_blank','width=944, height=584')" src="./
statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/460/280"
style="cursor:pointer"><div></div></div><br>
<div><img id="toto_3" onclick="window.open('./
statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/
920/560','_blank','width=944, height=584')" src="./
statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/460/280"
style="cursor:pointer"><div></div></div>

The id of the img is correctly incremented (toto_1, 2, 3...) But the
source of my image has always the same url:

"./statistics.dashboardview.enrollmentbenchmarkchart.toto:chart/ 
460/280"

That was built using "createActionLink"
What I was expecting was:
"./statistics.dashboardview.enrollmentbenchmarkchart.toto_1:chart/
460/280"
"./statistics.dashboardview.enrollmentbenchmarkchart.toto_2:chart/
460/280"
etc...
The problem seems to be related to the fact "getCompleteId" does not
generate a new id.
Now, obviously, I could put the data of my graph in my application
state then pass a context at the end of the url (after the 460/280)

then use that context to fetch the data from within my graph.  
However,

I feel this is not very good design. After all, if I have a loop with

several graphs being generated dynamically, I simply want to create  
as
many statefull graph objects as there are rows in my loop, each  
object

containing the data to draw, without binding strongly with an
application state.

Alex
Le 4 févr. 08 à 19:06, Chris Lewis a écrit :


It's difficult to respond as clearly we're not seeing all of the
code, but here one would assume that your custom component, in terms
of generated markup, is simply an img element. No action link will
have your generated id because you're not creating one in this code.
Rather you create and output only and img with the id generated by
T5, so if you look at the generated markup you should see the id
being correctly incremented, but it will be an attribute of the img

(and NOT a (action)link), because you aren't doing that in this  
code.


Alexander Lamb wrote:

Well, getting close, but not quite.

Indeed, the getClientId works fine, but since my component is
actually a graph (JFreeChart) being rendered from an URL, it looks
like the clientId is not pushed to the ActionLink created.

  @SuppressWarnings("unchecked")
  void beginRender(MarkupWriter writer) {

    _clientId =  
_renderSupport.allocateClientId(_resources.getId());

    System.out.println("--- CLIENT ID: " + _clientId);
    System.out.println("--- RESOURCES ID: " + _resources.getId());
    System.out.println("--- RESOURCES COMPLETE ID: " +
_resources.getCompleteId());
    //generate action link
    Link link = _resources.createActionLink("chart", false,
_width, _height);
    Element img = writer.element("img", "src", link, "id",
_clientId);

    if(_popupWidth == 0)
        _popupWidth = 2 * _width;
    if(_popupHeight == 0)
        _popupHeight = 2 * _height;
    link = _resources.createActionLink("chart", false,
_popupWidth, _popupHeight);
    img.attribute("onclick", "window.open('"+link
+"','_blank','width="+(_popupWidth+24)+", height="+(_popupHeight
+24)+"')");
    img.attribute("style", "cursor:pointer");

    _resources.renderInformalParameters(writer);
  }


My trace and the HTML source generated shows very well the clientId
is incremented correctly... but the ActionLink generated is not
(completeId stays always as the initial id).

Alex

Le 4 févr. 08 à 15:45, Chris Lewis a écrit :


Alex,

Id generation, as far as I know, does not come for free. If you
want to receive an id generated by T5, you have to explicitly
request it. You'll find this done in one of the parent classes of
the field elements - possibly in AbstractField. I've implemented
it the same way in several different components, one of which you
can see here:



http://code.google.com/p/gc-tapestry-components/source/browse/trunk/gc-tapestry5-components/src/main/java/net/godcode/t5c/components/SlideShow.java


The key parts are:

    @Inject
    private ComponentResources resources;
          @Environmental
    private PageRenderSupport renderSupport;
          /** The client-side id. */
    private String clientId;
          /* Render phase. */
          @SetupRender
    void setupRender() {
            clientId =
renderSupport.allocateClientId(resources.getId());
    }

And then making sure you insert clientId into your component tag's
id attribute. This could probably be isolated into a mixin, or you
could probably just extend AbstractField. That would make sense as
long as your component's behavior merits the semantics of a field
(which it doesn't seem to).

Hope that helps.

chris


Alexander Lamb wrote:

Hello list,

It looks like custom components are not statefull.

Indeed, I have a loop which contains a graph I generate and a
TextField (for testing purposes), and the generated code looks
like this:

<div><img src="./
statistics
.dashboardview
.enrollmentbenchmarkchart.monthserieslinechart:chart/460/280"></
div></div></td></tr><tr><td><input id="textfield_8"
name="textfield_8" type="text" value="ITALY"><img alt="[Error]"
class="t-error-icon t-invisible" id="textfield_8:icon"
src="assets/tapestry/field-error-marker.gif"><div> IT <div><img
src="./
statistics
.dashboardview
.enrollmentbenchmarkchart.monthserieslinechart:chart/460/280"></
div></div></td></tr><tr><td><input id="textfield_9"
name="textfield_9" type="text" value="NETHERLANDS"><img
alt="[Error]" class="t-error-icon t-invisible"
id="textfield_9:icon" src="assets/tapestry/field-error-
marker.gif"><div> NL <div><img src="./
statistics
.dashboardview
.enrollmentbenchmarkchart.monthserieslinechart:chart/460/280"></
div></div></td></tr><tr><td><input id="textfield_10"
name="textfield_10" type="text" value="NORWAY"><img alt="[Error]"
class="t-error-icon t-invisible" id="textfield_10:icon"
src="assets/tapestry/field-error-marker.gif"><div> NO
As you can see, my TextField gets incremented but not my
enrollmentbenchmarkchart !
Should I file a bug for this?
P.S. I tried to generate the ids but it didn't work.
Thanks,

Alex

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