[core] UIComponentBase.getId() can return null

[Matthias Wessendorf <ma...@apache.org>]

Hi,

Blake committed an interesting patch to Trinidad:
http://bit.ly/dtghOs

I see that MyFaces can actually return NULL on getId(), however the
MyFaces implementation
goes ahead and creates the ID if getClientId(facesCtx) is called AND!
the getId() returns null.

So, why not directly ensuring that getId() can't return null ?

Checking the JavaDoc of getClientId(FacesCtx), I see that MyFaces is
doing what is required.
But does that really make sense?

-Matthias

-- 
Matthias Wessendorf

blog: http://matthiaswessendorf.wordpress.com/
sessions: http://www.slideshare.net/mwessendorf
twitter: http://twitter.com/mwessendorf

Re: [core] UIComponentBase.getId() can return null

[Blake Sullivan <bl...@oracle.com>]

We need to fol,low up with the JSF spec because:

1) The RI does not implement the behavior you would expect from the 
JavaDoc because calling getClientId() on a component with a null id 
causes the id of the component to be set as a side-effect.  The expected 
result would be that the id of the component would not be set in this case

2) The behavior implied by the Javadoc (and the one I believe that 
MyFaces does and Trinidad tried to implement) is not useful.  I see no 
reason why it is preferable that the clientId of a not agree with the 
component's id just so that the component's id can sometimes be null.  
The only advantage of supporting a null id is lower memory usage for 
dynamically created components.

The other insidious side-effect of getId() being allowed to return null 
is that this caused problems with the JSF RI not having stable 
clientIds.  This led the RI to impement clientId caching.  The RI's 
implementation of clientId caching:

1) Requires special behavior on components that want to work with 
components that inherit from the RI's UIComponentBase

2) The RI doesn't correctly clear its caches in cases when it should  
(the id of a NamingContainer changes, thus affecting the clientIds of 
its descendants or a component is moved between NamingContainers, 
affecting both its and its descendants clientIds)

So, for JSF 2.1 we should also address clientId caching and at the very 
least have real apis for clearing the caches and have the spec actually 
define the required behavior.

-- Blake Sullivan


Matthias Wessendorf said the following On 2/9/2010 12:54 AM PT:
> Hi,
>
> Blake committed an interesting patch to Trinidad:
> http://bit.ly/dtghOs
>
> I see that MyFaces can actually return NULL on getId(), however the
> MyFaces implementation
> goes ahead and creates the ID if getClientId(facesCtx) is called AND!
> the getId() returns null.
>
> So, why not directly ensuring that getId() can't return null ?
>
> Checking the JavaDoc of getClientId(FacesCtx), I see that MyFaces is
> doing what is required.
> But does that really make sense?
>
> -Matthias
>
>   

Re: [core] UIComponentBase.getId() can return null

[Jakob Korherr <ja...@gmail.com>]

Hi,

So the difference between getId() and getClientId() is that the last one
generates the Id if necessary, am I right?

>From my point of view getId() is the getter for the id property which can be
set with setId(). However, there is no method setClientId(). So I think the
sence is that getId() returns non-null if the user assigned an id to the
component and null otherwise, whereas getClientId() always returns a valid
id, because it generates one if the component has no assigned id.

So you are able to check if the user assigned an id to the component if the
result of getId() is non-null. Nevertheless I don't know if that makes a lot
of sence...

Regards,
Jakob

2010/2/9 Matthias Wessendorf <ma...@apache.org>

> Hi,
>
> Blake committed an interesting patch to Trinidad:
> http://bit.ly/dtghOs
>
> I see that MyFaces can actually return NULL on getId(), however the
> MyFaces implementation
> goes ahead and creates the ID if getClientId(facesCtx) is called AND!
> the getId() returns null.
>
> So, why not directly ensuring that getId() can't return null ?
>
> Checking the JavaDoc of getClientId(FacesCtx), I see that MyFaces is
> doing what is required.
> But does that really make sense?
>
> -Matthias
>
> --
> Matthias Wessendorf
>
> blog: http://matthiaswessendorf.wordpress.com/
> sessions: http://www.slideshare.net/mwessendorf
> twitter: http://twitter.com/mwessendorf
>