Greets,
After converting my application from JSP to Facelets, I set out to make
my "rowStyleClass" attribute on t:dataTable work like it used to.
First, I had to get the attribute working in Facelets. With considerable
discussion on the user list (see [1] and [2]) and a lot of help from
Mike, I think we've identified some pretty simple code changes to enable
this and other similar attributes. I plan to introduce a patch for this,
probably tomorrow.
What happened next was that during testing of this change, I could
confirm that the attribute did indeed now work, but I was baffled by
unexpected behaviour. My EL expression which had previously returned
null in certain situations was now returning the empty String. I went to
Facelets list for some clarification on this (see [3]) and it turned out
to be a requirement of the new EL spec to coerce the nulls into empty
string.
Getting an empty String instead of null for this ValueBinding lookup
creates a problem because the extended dataTable treats a null value
differently and goes looking at the more standard style attributes like
rowClasses. With an empty string returned, it assumes it needs to look
no further. As a user, there is no way for me to specify that under
certain conditions, it should fallback to the other style attributes,
e.g. rowClasses.
The best fix we have collectively come up with so far is to coerce the
empty string back into a null in the dataTable, so that the renderer
does the right thing. I don't see too much downside to this approach, as
an empty style string has no relevance in CSS. However, I feel a
proposed change like this requires extra discussion before making a
decision on it. It's another one of those situation where we have to
decide how we want to handle unexpected results due to changes in the
newer specs.
If you review the threads a bit, you can see more of the details of the
issues. I'll post my preliminary proposed code changes at the bottom.
[1] https://facelets.dev.java.net/servlets/ReadMsg?list=users&msgNo=6875
[2]
http://www.nabble.com/Re%3A-Facelets-support-for-a-Tomahawk-dataTable-trick--tf3236491.html
[3] https://facelets.dev.java.net/servlets/ReadMsg?list=users&msgNo=6941
Regards,
Jeff Bischoff
Kenneth L Kurz & Associates, Inc.
Okay proposed code change in
org.apache.myfaces.component.html.ext.HtmlDataTable
Original Method:
public String getRowStyleClass()
{
if (_rowStyleClass != null)
return _rowStyleClass;
ValueBinding vb = getValueBinding(JSFAttr.ROW_STYLECLASS_ATTR);
return vb != null ? (String) vb.getValue(getFacesContext()) : null;
}
New Method:
public String getRowStyleClass()
{
if (_rowStyleClass != null)
return _rowStyleClass;
// TODO: temporarily support fully-qualified ext. dataTable
attribute names.
ValueBinding vb =
getValueBinding("org.apache.myfaces.dataTable.ROW_STYLECLASS");
if (vb != null)
log.warn("org.apache.myfaces.dataTable.ROW_STYLECLASS is
deprecated. Please use rowStyleClass instead.");
else
vb = getValueBinding(JSFAttr.ROW_STYLECLASS_ATTR);
if(vb == null)
return null;
String bindingValue = (String) vb.getValue(getFacesContext());
if(bindingValue == "")
return null; // Fix for JSF 1.2 EL coercing nulls to empty string
return bindingValue;
}
That, along with the change to JSFAttr to change the constant value from
"org.apache.myfaces.dataTable.ROW_STYLECLASS" to "rowStyleClass". NOTE:
This change affects the shared code!
