Gentry, Michael (Contractor) wrote:
I've downloaded and tried out the prop: prefix extension from HLS. One
thing I was *really* hoping for, compared to OGNL, is that it would
ignore null pointers, at least on reads.
OGNL has a feature called NullHandlers
You contribute one to configuration point tapestry.ognl.NullHandlers
like this
<null-handler class="class.having.null.properties"
object="instance:org.MyNullHandler"/>
where MyNullHandler implements
http://www.ognl.org/2.6.9/Documentation/javadoc/ognl/NullHandler.html
So, if you have a RegisterPage that contains a path like
user.department.name you have
to register null handlers (could be the same one) for the following :
RegisterPage (cause its user may be null),
User (cause his department may be null)
I have report-type pages
(read-only) where I can sometimes have thousands of rows with 10-15
columns. Each of those columns currently has bulky cover methods which
do NPE protection in case a relationship is missing (the actual values
almost always come from a dotted path: foo.bar.baz.status, and OGNL will
blow up if "bar" is null). I was hoping the prop: extension would
handle this, but it seems to work just like OGNL if it hits a null. If
something doesn't exist, I'm pretty happy with just getting a null back
and displaying nothing.
I played with the code a bit and this seems to work if you edit
PropertyAccessorBinding.java and change the getObject() method:
public Object getObject()
{
return _accessor.readProperty();
} <http://www.len.ro/work/articles/tapestry-ajax-application-1/>
to:
public Object getObject()
{
try
{
return _accessor.readProperty();
}
catch (NullPointerException exception)
{
// Ignore NPE on reads ...
return null;
}
}
A) Does this seem like a reasonable thing to do?
B) If yes to A, could it maybe be included in the actual prop: package
(would beat maintaining a separate branch).
Thanks!
/dev/mrg
PS. I didn't alter setObject() ... I'd consider that an actual error if
you were trying to set things through nulls.
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Andreas Andreou - [EMAIL PROTECTED] - http://andyhot.di.uoa.gr
Tapestry / Tacos developer
Open Source / J2EE Consulting
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