[seam-dev] Suppressing parameter inclusion for s:link

[Pete Muir]

On 24 Oct 2008, at 20:10, Dan Allen wrote:

> Pete feels that I clouded the issue with my previous response. I will
> try again this time addressing Christian's proposal directly.

Thanks :-)

>
>
> On Fri, Oct 24, 2008 at 7:48 AM, Christian Bauer
> <christian.bauer at gmail.com> wrote:
>>
>> On Oct 24, 2008, at 13:21 , Pete Muir wrote:
>>
>>> As Christian said, <f:param name="whatever" /> is probably the wrong
>>> syntax for this, as it implies you are adding a parameter, not  
>>> removing it.
>>> Maybe we need an <s:suppressPageParameter name="foo" /> instead.
>>
>> -1, just document <f:param name="foo" value="#{null}"/> and that's  
>> it for
>> suppressing a page parameter. Overriding is then consistent with  
>> <f:param
>> name="foo" value="#{override}"/>. This would be the easiest  
>> solution. Any
>> syntax we come up with to do the same in a different way is going  
>> to be more
>> complex.
>
> Agreed.
>
> Also, these two are exactly the same in the eyes of Facelets:
> <f:param name="foo"/>
> <f:param name="foo" value="#{null}"/>
> We cannot enforce one or the other since Facelets doesn't enforce one
> or the other.

Actually it is possible to differentiate between the two in JSF  
(nothing to do with facelets).

if (parameter.getValueExpression("value") == null) {
    // The markup was <f:param name="foo"/>
} else if (parameter.getValue() == null) {
  / // The markup was <f:param name="foo" value="#{null}"/>
}

>
>
>> Or/and we do this:
>>
>> <page view-id="one.xhtml">
>> <param name="foo" value="#{binding.getterAndSetter"/>
>> <param name="bar" value="#{binding.getterAndSetter"/>
>> </page>
>>
>> Regular link that evaluates #{binding.getterAndSetter} to get the  
>> "foo" and
>> "bar" parameter values (that's the (current) default):
>>
>> <s:link view-id="one.xhtml" page-parameters="override"/>
>
> I don't get the point of "override" here. Let's just keep the current
> behavior of incorporating the page parameters into the URL as the
> default.
>
> <s:link view="/one.xhtml" value="One"/>
>
>> Link that only contains the "bar" parameter with  
>> #{binding.getterAndSetter}
>> value:
>>
>> <s:link view-id="one.xhtml" page-parameters="override">
>> <f:param name="foo"/>
>> </s:link:
>
> Yep, this was the logic I just added in Seam 2.1. As you mentioned
> above, you could also do <f:param name="foo" value="#{null}"/>. I
> still don't see the need for the "override". The very presence of
> <f:param> implies an override.

Christian, did you mean it this way around? To me, this syntax would  
create a link that only had the *foo* parameter (that's the way you  
described it to me on IM):

<s:link view="one.xhtml" pageParameters="override">
    <f:param name="foo"/>
</s:link>

and this only a bar parameter:

<s:link view="one.xhtml" pageParameters="override">
    <f:param name="bar"/>
</s:link>

So, specifying override requires you to specify any parameters you  
want to propagate on the link. Specifying a param without the value  
will cause the default value to be used from pages.xml, or you can  
specify a value.


>
>
>> Link that only contains the "bar" parameter with #{binding.other}  
>> value:
>>
>> <s:link view-id="one.xhtml" page-parameters="override">
>> <f:param name="foo"/>
>> <f:param name="bar" value="#{binding.other}"/>
>> </s:link:>
>
> Agreed, but again, don't need the "override".

So in my scheme, this would propagate both foo and bar, with foo using  
it's default value.
>
>
>> Link that only contains the "foo" parameter with  
>> #{binding.getterAndSetter}
>> value:
>>
>> <s:link view-id="one.xhtml" page-parameters="ignore">
>> <f:param name="foo"/>
>> </s:link>

Under my scheme we don't need "ignore" , you would use:

<s:link view="one.xhtml" pageParameters="override">
    <f:param name="foo"/>
</s:link>


>>
>
> The general idea is correct here, except foo is only included if a
> value is provided (to be consistent with what was said above). I also
> have a different idea for the attribute that controls the use of the
> page parameters. How about this?
>
> <s:link view="/one.xhtml" value="One" encodePageParameters="false">
>  <f:param name="foo" value="anyOldValue"/>
> </s:link>

Encode isn't right, as that (to me) refers to encoding the parameter  
strings.

>
>
>> Link that only includes the "foo" parameter with #{binding.other}  
>> value:
>>
>> <s:link view-id="one.xhtml" page-parameters="ignore">
>> <f:param name="foo" value="#{binding.other}"/>
>> </s:link>

This is really the same as

<s:link view="one.xhtml" pageParameters="override">
    <f:param name="foo" value="#{binding.other}" />
</s:link>

>>
>
> And again my suggestion:
>
> <s:link view="/one.xhtml" value="One" encodePageParameters="false">
>  <f:param name="foo" value="#{binding.other}"/>
> </s:link>
>
>> The advantage here is that we can keep it backwards compatible, if  
>> you have
>> the default page-parameters="override", the #{null} trick, the ""  
>> value
>> trick, and the no-value-attribute all continue to work as before.

I'm really not sure that the no-value-attribute is correct, so I think  
we should change it to your original suggestion Christian - that it  
causes a parameter to be propagated with the value got from pages.xml.  
I think as this is a new minor feature we can break it.

>>
>
> Yes, this is definitely going to be easy to make backward compatible.
> By default it will encode the page parameters unless the
> encodePageParameters="false" is added to the Seam command component.
> The name for this attribute is open to discussion. Recall that we need
> this attribute on the <redirect> component in the page descriptor as
> well.