Hi,
JSF must send down to the browser a list of (label,value) pairs for the
user to select from, and then on postback the browser sends back the
value part of the selected item. The label and value must both be
strings; this is required by html. Therefore a converter of some sort is
definitely needed in order to generate appropriate "value" strings for
the items when rendering the page, and on postback the renderer must be
able to map back from the selected "value" to the appropriate item object.
Doing this conversion automatically is clearly not possible, so an
appropriate converter must be provided. For the case where the items to
be selected from are persistent entities, the converter should generally
write out the "key" of the object, and on postback retrieve the object
using the key.
Maybe one option is for the select* components on render to use the
index into the list of items as the value. Then on postback, as long as
the same list of objects is available then it could map back from index
to object. This would need some more thought though; for example this is
valid:
<h:selectOneMenu>
<f:selectItem ..>
<f:selectItems ..>
<f:selectItem ..>
</h:selectOneMenu>
which would complicate computing an index. And I think this
functionality would need to be in the t:selectOneMenu etc, as the
t:selectItems component is only used at render time, and is not used to
process the postback data AFAIK. Or this idea may be complete rubbish; I
haven't thought about it for long..
As Cagatay says, you can register a "global" converter for each of your
persistent classes within a faces-config.xml file. Then it will be used
automatically rather than you having to define the converter within each
t:selectItems or f:selectItems tag.
Regards,
Simon
Cagatay Civici schrieb:
Conversions are the nature of jsf so it really makes sense to use a
converter for t:selectItems.
Generally the common solution is two write a generic jpa entity
converter if you are using jpa with jsf.
Using the converter-for-class kinda config once, you dont need to
define the converter each time you use it.
On Wed, Sep 10, 2008 at 7:22 AM, mjdenham <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
I was wondering if t:selectItems could be enhanced to work without a
converter because it has the list of all the domain objects.
My code is similar to this:
<h:selectOneMenu value="#{order.carPart}">
<t:selectItems value="#{carParts}" var="part" itemValue="#{part}"
itemLabel="#{part.name <http://part.name>}" />
</h:selectOneMenu>
public class Order {
private CarPart carPart;
...
}
t:selectItems automatically generates SelectItem objects for us
but it would
be nice if it also allowed objects to be assigned to the actual
selectOneMenu e.g. order.carPart value without requiring a
Converter. Is it
possible?
I tried and get a null Converter error.
Thanks
Martin
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