Hi
I see.
BS>> Also, to avoid duplicates and/or unnecessary re-rendering, all so far
rendered
BS>> resources must be remembered in JSF state. AFAIC this is currently not
the case.
Well, this is information related to the view that is implicit there, but
you want to
avoid to put it in the state.
That's the reason why I like the way it is working in MyFaces, because we
just keep
track of the change, rather than store that information in the state.
Write the script directly into the <eval> is possible, but right now from
spec
perspective there are not the necessary "building blocks" available.
Both h:outputScript and h:outputStylesheet are components that are supposed
to be
rendered as resources, but both components have Renderer instances, which
are
the classes who finally decide how they should be rendered. Even if you
have a list,
this list could include javascript/css or whatever and the resources could
be rendered
in different ways.
For example an h:outputScript could have children that could be js code. Or
a
h:outputStylesheet could have a "media" property set.
So if we want a "general" solution to the problem, which includes script,
stylesheets
or whatever, it is necessary to know the component instance that needs to
be added
or updated, and then ask the component how it should be rendered.
The problem from the "building blocks" perspective, is there is no way the
component
can know the current request is an ajax update. encodeAll(...) just means
encode
everything and don't ask questions.
I would like to have a method in UIComponent/Renderer called
encodeAjax(...) for the
component, which by default start and end an <update> section and call by
default
to encodeAll(...). Something like this
public void encodeAjax(FacesContext _facesContext, PartialResponseWriter
writer) {
try
{
writer.startUpdate(target.getClientId(_facesContext));
target.encodeAll(_facesContext);
}
finally
{
writer.endUpdate();
}
}
This part is done in PartialViewContext implementation, but if we can move
it here
we could ask the component in a gentle way how it should be rendered. Then,
from
this location we could override the method and call writer.startEval(...),
which is
something is not possible in this moment, because there is no way right now
to
customize this step for each component.
In this way, you could add an script to load the stylesheet and then use
the eval
to include it in the response.
I have already mention this improvement in this mail some time ago:
https://java.net/projects/javaserverfaces-spec-public/lists/jsr372-experts/archive/2015-04/message/41
It looks we have yet another use case where this could be useful.
regards,
Leonardo Uribe
2016-06-21 14:51 GMT+02:00 Bauke Scholtz <balusc_at_gmail.com>:
> Hi,
>
> OmniFaces has 3 solutions to dynamically include a (script) resource:
>
> 1: Ajax#load() (just write script straight to <eval>)
> 2: Components#addScriptResourceToHead()
> 3: Components#addScriptResourceToBody()
>
> Which one to use depends on the moment (which isn't yet refactored into a
> single utility method, this is TBD). When the request is an ajax request
> with partial rendering (i.e. ajax with NO @all), then use #1. Else when the
> current phase is NOT render response, or the view is in BUILDING state,
> then use #2. Else use #3.
>
> This is implemented for the unload script associated with OmniFaces
> @ViewScoped and this works quite well.
>
> Also, to avoid duplicates and/or unnecessary re-rendering, all so far
> rendered resources must be remembered in JSF state. AFAIC this is currently
> not the case.
>
> Cheers, B
>
>
> On Tue, Jun 21, 2016 at 2:37 PM, Leonardo Uribe <leonardo.uribe_at_irian.at>
> wrote:
>
>> Hi
>>
>> I have seen this issue has been opened in the spec issue tracker
>>
>> https://java.net/jira/browse/JAVASERVERFACES_SPEC_PUBLIC-1423
>> Dynamic resource loading in ajax requests
>>
>> I would like to contribute with some thoughts about the topic, since in
>> MyFaces there
>> is a solution that is not perfect (if PartialViewContext is overriden,
>> the code will
>> not work, so some third party libraries will not be able to use it), but
>> it helps to
>> identify the missing points in the spec, and specify it faster.
>>
>> This issue could be also relevant for portlets.
>>
>> The issue has been reported long time ago in:
>>
>> - https://issues.apache.org/jira/browse/MYFACES-3106
>> Resources not loaded when using a dynamic ui:inlclude and rendered via
>> ajax
>>
>> - https://issues.apache.org/jira/browse/MYFACES-3367
>> Detect when to update head or body target when content has been updated
>> dynamically
>>
>> - https://issues.apache.org/jira/browse/MYFACES-3659
>> Conditional include of scripts and stylesheets
>>
>> The first thing to understand the problem is identify the possible use
>> cases we have:
>>
>> - c:if, ui:include src="#{...}" or facelet tag that dynamically update
>> the tree.
>>
>> For example:
>>
>> ...
>> <f:ajax event="onclick" render="box"/>
>> ...
>>
>> <div jsf:id="box">
>> <c:if test="#{...}">
>> <h:outputScript target="head" library="js" name="help.js" />
>>
>> ...
>> </c:if>
>> </div>
>>
>> Here we have a case when the components inside the c:if requires some
>> javascript file,
>> but the update comes from an ajax request. The algorithm just somehow put
>> the
>> h:outputScript on the head of the document, but the ajax does not trigger
>> the head
>> refresh, so the component was added to the tree, but the javascript file
>> was not loaded
>> and we finally have a broken panel.
>>
>> There are variants of the same example with h:outputStylesheet, or
>> ui:include but the
>> reason is the same.
>>
>> - Dynamic but the resource is added by a @ResourceDependency annotation.
>>
>> This is similar to the previous case, but the component is added
>> indirectly when
>> Application.createComponent(...) is executed.
>>
>> The important thing to keep in mind is there are 3 possible targets:
>> "head", "body" and
>> "form". But the only thing we can do with the current spec is just force
>> a full update
>> of each of these targets.
>>
>> So, in MyFaces there is a web config param called
>> org.apache.myfaces.STRICT_JSF_2_REFRESH_TARGET_AJAX that when it is
>> activated, and
>> the previous situation happens, it just enable a flag so the target is
>> updated with
>> the ajax request. If the "head" needs to be updated, the whole "head" and
>> the updated
>> content is sent and so on.
>>
>> The processing is done on process partial render time, after the ajax
>> request is
>> rendered but before write the state token. Please note if the target is
>> rendered before
>> this code, the algorithm should be able to detect the condition and do
>> not duplicate
>> the response.
>>
>> The solution is not perfect because it force render the whole target,
>> when we only
>> need to render the html fragment of the added component
>> (script/stylesheet/
>> other js code). But there is no way to do it with the current API,
>> because <head>
>> or <body> could not have an id and without id, you can't insert.
>> PartialResponseWriter
>> contains these methods:
>>
>> startInsertBefore(String targetId)
>> startInsertAfter(String targetId)
>>
>> But note these two are useless, because what we need is insert "inside"
>> at the beginning
>> or the end.
>>
>> For example:
>>
>> <head>
>>
>> <script .../>
>> </head>
>>
>> <body>
>> <script .../>
>>
>> </body>
>>
>> Please note there are some cases where the jsf third party library (for
>> example
>> primefaces) provides its own rules to to render the script at first,
>> middle or last. But
>> in this case it doesn't matter those rules, because what we really need
>> is that the
>> resource is added.
>>
>> The code that activates the flags to render head, body or form target is
>> on
>> h:outputScript and h:outputStylesheet, specifically in the listener
>> attached to
>> PostAddToViewEvent. This is the best place, because here is the place
>> where
>> UIViewRoot.addComponentResource is done.
>>
>>
>>
>> I think what's really important in this problem is provide the API where
>> you can notify
>> that the resource needs to be added. In MyFaces there is:
>>
>> class RequestViewContext {
>>
>> public boolean isRenderTarget(String target);
>>
>> public void setRenderTarget(String target, boolean value);
>>
>> }
>>
>> Which could evolve to something more complex, including the UIComponent
>> instance and
>> so on.
>>
>> I don't really like to do a list comparison, because it can introduce an
>> unnecessary
>> performance overhead. I would like an API that could have some methods to
>> register the
>> component for updated on the target and others to get the changes and do
>> the necessary
>> calculation in PartialViewContext.processPartial(...) (render response).
>>
>> regards,
>>
>> Leonardo Uribe
>>
>
>