The source for tapestry-prop is available.
If I were doing this, I would change how it generates code to check
for the nulls as it goes, rather than forcing an NPE. Further, when
accessing a property, there's always the potential that the terminal
property accessor method throws the NPE which you wouldn't want to
mask. So handle nulls by checking for nulls.
I don't believe in baking this into tapestry-prop, I try to code in
the "don't expect null, don't return null" vein. You can do a lot
with Collections.EMPTY_LIST and flyweight placeholders to prevent
NPEs.
On 1/30/07, Gentry, Michael (Contractor) <[EMAIL PROTECTED]> 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. 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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