Re: Tapestry prop: suggestion (or question)
Probably dangerous but nice...or,
probably nice but dangerous ;-)
Anyway, perhaps this can find its way in our wiki.
http://wiki.apache.org/tapestry/
On 4/6/07, Drew McAuliffe <[EMAIL PROTECTED]> wrote:
You can also do what I did and just contribute a brand new expression
evaluator:
public class NullSafeExpressionEvaluator extends ExpressionEvaluatorImpl
{
private static Logger log = Logger.getLogger(
NullSafeExpressionEvaluator.class);
private static final String START_BRACKET = "{";
private static final String ESCAPED_BRACKET = START_BRACKET;
private static final String END_BRACKET = ESCAPED_BRACKET;
public Object readCompiled(Object target, Object expression){
Object result = null;
try{
result = super.readCompiled(target, expression);
}
catch (ApplicationRuntimeException e){
if (!(e.getRootCause() instanceof NullPointerException))
result = "";
// don't do anything!
}
return result;
}
}
HIVEMIND:
On 1/31/07, andyhot <[EMAIL PROTECTED]> wrote:
>
> Gentry, Michael (Contractor) wrote:
> > I get an error trying to contribute to tapestry.ognl.NullHandlers ...
> > Is that available in T4? Thanks!
> >
>
> Damn, that's 4.1 only...
> If you're on 4.0.x, you can still do this, but you'll have to register
> the handlers on your own.
>
> You just have to call OgnlRuntime's static method at a convenient time,
> i.e. on app startup
>
> OgnlRuntime.setNullHandler(subjectClass, handler);
>
> That's exactly what happens in
>
>
http://svn.apache.org/viewvc/tapestry/tapestry4/trunk/tapestry-framework/src/java/org/apache/tapestry/services/impl/ExpressionEvaluatorImpl.java?view=markup
>
>
>
> >
> > The electronic mail message you have received and any files
transmitted
> > with it are confidential and solely for the intended addressee(s)'s
> > attention. Do not divulge, copy, forward, or use the contents,
> > attachments, or information without permission of Fannie Mae.
> > Information contained in this message is provided solely for the
purpose
> > stated in the message or its attachment(s) and must not be disclosed
to
> > any third party or used for any other purpose without consent of
Fannie
> > Mae. If you have received this message and/or any files transmitted
with
> > it in error, please delete them from your system, destroy any hard
> > copies of them, and contact the sender.
> >
> >
> > -Original Message-
> > From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
> > Sent: Tuesday, January 30, 2007 12:15 PM
> > To: Tapestry users
> > Subject: Re: Tapestry prop: suggestion (or question)
> >
> > 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
> > > 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
Re: Tapestry prop: suggestion (or question)
You can also do what I did and just contribute a brand new expression
evaluator:
public class NullSafeExpressionEvaluator extends ExpressionEvaluatorImpl
{
private static Logger log = Logger.getLogger(
NullSafeExpressionEvaluator.class);
private static final String START_BRACKET = "{";
private static final String ESCAPED_BRACKET = START_BRACKET;
private static final String END_BRACKET = ESCAPED_BRACKET;
public Object readCompiled(Object target, Object expression){
Object result = null;
try{
result = super.readCompiled(target, expression);
}
catch (ApplicationRuntimeException e){
if (!(e.getRootCause() instanceof NullPointerException))
result = "";
// don't do anything!
}
return result;
}
}
HIVEMIND:
On 1/31/07, andyhot <[EMAIL PROTECTED]> wrote:
Gentry, Michael (Contractor) wrote:
> I get an error trying to contribute to tapestry.ognl.NullHandlers ...
> Is that available in T4? Thanks!
>
Damn, that's 4.1 only...
If you're on 4.0.x, you can still do this, but you'll have to register
the handlers on your own.
You just have to call OgnlRuntime's static method at a convenient time,
i.e. on app startup
OgnlRuntime.setNullHandler(subjectClass, handler);
That's exactly what happens in
http://svn.apache.org/viewvc/tapestry/tapestry4/trunk/tapestry-framework/src/java/org/apache/tapestry/services/impl/ExpressionEvaluatorImpl.java?view=markup
>
> The electronic mail message you have received and any files transmitted
> with it are confidential and solely for the intended addressee(s)'s
> attention. Do not divulge, copy, forward, or use the contents,
> attachments, or information without permission of Fannie Mae.
> Information contained in this message is provided solely for the purpose
> stated in the message or its attachment(s) and must not be disclosed to
> any third party or used for any other purpose without consent of Fannie
> Mae. If you have received this message and/or any files transmitted with
> it in error, please delete them from your system, destroy any hard
> copies of them, and contact the sender.
>
>
> -Original Message-
> From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
> Sent: Tuesday, January 30, 2007 12:15 PM
> To: Tapestry users
> Subject: Re: Tapestry prop: suggestion (or question)
>
> 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
> 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
Re: Tapestry prop: suggestion (or question)
Gentry, Michael (Contractor) wrote:
I get an error trying to contribute to tapestry.ognl.NullHandlers ...
Is that available in T4? Thanks!
Damn, that's 4.1 only...
If you're on 4.0.x, you can still do this, but you'll have to register
the handlers on your own.
You just have to call OgnlRuntime's static method at a convenient time,
i.e. on app startup
OgnlRuntime.setNullHandler(subjectClass, handler);
That's exactly what happens in
http://svn.apache.org/viewvc/tapestry/tapestry4/trunk/tapestry-framework/src/java/org/apache/tapestry/services/impl/ExpressionEvaluatorImpl.java?view=markup
The electronic mail message you have received and any files transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the purpose
stated in the message or its attachment(s) and must not be disclosed to
any third party or used for any other purpose without consent of Fannie
Mae. If you have received this message and/or any files transmitted with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
-Original Message-
From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
Sent: Tuesday, January 30, 2007 12:15 PM
To: Tapestry users
Subject: Re: Tapestry prop: suggestion (or question)
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
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.
The electronic mail message you have received and any files
transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the
purpose
stated in the message or its attachment(s) and must not be disclosed
to
any third party or used for any other purpose without consent of
Fannie
Mae. If you have received this message and/or any files transmitted
with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
--
Andreas Andreou - [EMAIL PROTECTED] - http://andyhot.di.uoa.gr
Tapestry / Tacos developer
Open Source / J2EE Consulting
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
RE: Tapestry prop: suggestion (or question)
I get an error trying to contribute to tapestry.ognl.NullHandlers ...
Is that available in T4? Thanks!
The electronic mail message you have received and any files transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the purpose
stated in the message or its attachment(s) and must not be disclosed to
any third party or used for any other purpose without consent of Fannie
Mae. If you have received this message and/or any files transmitted with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
-Original Message-
From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
Sent: Tuesday, January 30, 2007 12:15 PM
To: Tapestry users
Subject: Re: Tapestry prop: suggestion (or question)
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
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.
>
>
> The electronic mail message you have received and any files
transmitted
> with it are confidential and solely for the intended addressee(s)'s
> attention. Do not divulge, copy, forward, or use the contents,
> attachments, or information without permission of Fannie Mae.
> Information contained in this message is provided solely for the
purpose
> stated in the message or its attachment(s) and must not be disclosed
to
> any third party or used for any other purpose without consent of
Fannie
> Mae. If you have received this message and/or any files transmitted
with
> it in error, please delete them from your system, destroy any hard
> copies of them, and contact the sender.
>
>
>
>
>
--
Andreas Andreou - [EMAIL PROTECTED] - http://andyhot.di.uoa.gr
Tapestry / Tacos developer
Open Source / J2EE Consulting
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
RE: Tapestry prop: suggestion (or question)
Good point. They all inherit from CayenneDataObject. I'll try to give
that a test in a bit. Thanks!
The electronic mail message you have received and any files transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the purpose
stated in the message or its attachment(s) and must not be disclosed to
any third party or used for any other purpose without consent of Fannie
Mae. If you have received this message and/or any files transmitted with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
-Original Message-
From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
Sent: Tuesday, January 30, 2007 12:50 PM
To: Tapestry users
Subject: Re: Tapestry prop: suggestion (or question)
Gentry, Michael (Contractor) wrote:
> I had seen the null handlers before, but was trying to avoid
registering
> 100+ handlers. :-)
>
well, perhaps they all share a common super type...
> Thanks,
>
> /dev/mrg
>
>
>
> The electronic mail message you have received and any files
transmitted
> with it are confidential and solely for the intended addressee(s)'s
> attention. Do not divulge, copy, forward, or use the contents,
> attachments, or information without permission of Fannie Mae.
> Information contained in this message is provided solely for the
purpose
> stated in the message or its attachment(s) and must not be disclosed
to
> any third party or used for any other purpose without consent of
Fannie
> Mae. If you have received this message and/or any files transmitted
with
> it in error, please delete them from your system, destroy any hard
> copies of them, and contact the sender.
>
>
> -Original Message-
> From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
> Sent: Tuesday, January 30, 2007 12:15 PM
> To: Tapestry users
> Subject: Re: Tapestry prop: suggestion (or question)
>
> 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
> 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
>
>&
Re: Tapestry prop: suggestion (or question)
Gentry, Michael (Contractor) wrote:
I had seen the null handlers before, but was trying to avoid registering
100+ handlers. :-)
well, perhaps they all share a common super type...
Thanks,
/dev/mrg
The electronic mail message you have received and any files transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the purpose
stated in the message or its attachment(s) and must not be disclosed to
any third party or used for any other purpose without consent of Fannie
Mae. If you have received this message and/or any files transmitted with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
-Original Message-
From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
Sent: Tuesday, January 30, 2007 12:15 PM
To: Tapestry users
Subject: Re: Tapestry prop: suggestion (or question)
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
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.
The electronic mail message you have received and any files
transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the
purpose
stated in the message or its attachment(s) and must not be disclosed
to
any third party or used for any other purpose without consent of
Fannie
Mae. If you have received this message and/or any files transmitted
with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
--
Andreas Andreou - [EMAIL PROTECTED] - http://andyhot.di.uoa.gr
Tapestry / Tacos developer
Open Source / J2EE Consulting
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: Tapestry prop: suggestion (or question)
Sometimes it might make sense to have a setObject( ) with a little bit different behavior... namely, if elements of the property path are null then try to instantiate them, but ignore setObject( ) calls where the value to set is null and one of the property path elements is also null. I've taken this approach in the past with reflection-based bindings, and it's been pretty nice. On 1/30/07, Gentry, Michael (Contractor) <[EMAIL PROTECTED]> wrote: PS. I didn't alter setObject() ... I'd consider that an actual error if you were trying to set things through nulls.
RE: Tapestry prop: suggestion (or question)
I had seen the null handlers before, but was trying to avoid registering
100+ handlers. :-)
Thanks,
/dev/mrg
The electronic mail message you have received and any files transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the purpose
stated in the message or its attachment(s) and must not be disclosed to
any third party or used for any other purpose without consent of Fannie
Mae. If you have received this message and/or any files transmitted with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
-Original Message-
From: andreas a [mailto:[EMAIL PROTECTED] On Behalf Of andyhot
Sent: Tuesday, January 30, 2007 12:15 PM
To: Tapestry users
Subject: Re: Tapestry prop: suggestion (or question)
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
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.
>
>
> The electronic mail message you have received and any files
transmitted
> with it are confidential and solely for the intended addressee(s)'s
> attention. Do not divulge, copy, forward, or use the contents,
> attachments, or information without permission of Fannie Mae.
> Information contained in this message is provided solely for the
purpose
> stated in the message or its attachment(s) and must not be disclosed
to
> any third party or used for any other purpose without consent of
Fannie
> Mae. If you have received this message and/or any files transmitted
with
> it in error, please delete them from your system, destroy any hard
> copies of them, and contact the sender.
>
>
>
>
>
--
Andreas Andreou - [EMAIL PROTECTED] - http://andyhot.di.uoa.gr
Tapestry / Tacos developer
Open Source / J2EE Consulting
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: Tapestry prop: suggestion (or question)
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
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();
}
Re: Tapestry prop: suggestion (or question)
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();
}
RE: Tapestry prop: suggestion (or question)
Please ignore the hyperlink that showed up in the code snippet... It
wasn't there when I was typing the e-mail. Gotta love MS. :-)
The electronic mail message you have received and any files transmitted
with it are confidential and solely for the intended addressee(s)'s
attention. Do not divulge, copy, forward, or use the contents,
attachments, or information without permission of Fannie Mae.
Information contained in this message is provided solely for the purpose
stated in the message or its attachment(s) and must not be disclosed to
any third party or used for any other purpose without consent of Fannie
Mae. If you have received this message and/or any files transmitted with
it in error, please delete them from your system, destroy any hard
copies of them, and contact the sender.
-Original Message-
From: Gentry, Michael (Contractor) [mailto:[EMAIL PROTECTED]
Sent: Tuesday, January 30, 2007 9:03 AM
To: Tapestry users
Subject: Tapestry prop: suggestion (or question)
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();
}
