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Posted to users@tapestry.apache.org by Angelo Luis <an...@gmail.com> on 2006/04/24 19:33:20 UTC
Navigate in the object graph in tapestry!!!
I have a Client that have a Adrress and i want to navigate in the object
graph in that way : client.address.street, without have a null pointer
exception... how can i do that...
I kwon that i can do that with webwork. is that a way to do in tapestry???
Both (tapestry and ww) uses OGNL, so ....
PS; sorry for my english!
Re: Navigate in the object graph in tapestry!!!
Posted by Eduardo Valentim <va...@gmail.com>.
Andy,
I have the same issue, but a have found a solution (I think).
I made a little modification in this class
http://fisheye5.cenqua.com/viewrep/xwork/src/java/com/opensymphony/xwork/util/InstantiatingNullHandler.java from WebWork to work for me and override the method readCompiled from the class org.apache.tapestry.services.impl.ExpressionEvaluatorImpl as follow:
public class CustomExpressionEvaluatorImpl extends
ExpressionEvaluatorImpl {
private static InstantiatingNullHandler handler;
private InstantiatingNullHandler getHandler() {
if (handler == null) {
nhandler = new InstantiatingNullHandler();
}
return handler;
}
public Object readCompiled(Object target, Object expression) {
if (target != null) {
OgnlRuntime.setNullHandler(target.getClass, getHandler());
}
return super.readCompiled(target, expression);
}
}
and to put this class to work I have to override the service point
tapestry.ognl.ExpressionEvaluator.
<implementation service-id="tapestry.ognl.ExpressionEvaluator">
<invoke-factory service-id="hivemind.BuilderFactory" model="singleton" >
<construct class="package.CustomExpressionEvaluatorImpl" >
<set-object property="applicationSpecification" value="infrastructure:applicationSpecification" />
<set-configuration configuration-id="PropertyAccessors" property="contributions" />
</construct>
</invoke-factory>
</implementation>
See this link http://jakarta.apache.org/hivemind/override.html that
describe how to do this.
finally, whe my application loads, all is fine, but all this
configuration fails when I request the first page of application because
Hivemind say that CustomExpressionEvaluatorImpl dont have an property
called applicationSpecification but ExpressionEvaluatorImpl have a
method setApplicationSpecification() and I don't know what's happen.
I need a little help here, and this issue is solved. ;)
Thanks in Advances.
Eduardo Valentim
On Mon, 2006-04-24 at 22:57 +0300, andyhot@di.uoa.gr wrote:
> I remember last year, someone wanted to do the same thing...
> and he succeeded by patching ognl.
>
> Looking at the link you provided, it seems that one can simply do
> a OgnlRuntime.setNullHandler. Have you tried that?
>
> However, an additional configuration point for this ognl
> setting would be nice...
> According to
> http://jakarta.apache.org/tapestry/tapestry/hivedocs/module/tapestry.ognl.html
> we only support custom property accessors.
> Please add a bug report for this...
>
> >From Angelo Luis <an...@gmail.com>:
>
> > In webwork if the property is null the ww construct the object, and i think
> > that's use OGNL to do this,
> > http://www.opensymphony.com/ognl/html/DeveloperGuide/nullHandler.html ...
> >
> >
> > This is the part of WW in Action (Manning) that talk about that... Maybe,
> > Tapestry implement htis some day (as soon as possible, hehe)
> >
> > As you become more familiar with writing WebWork applications, you'll often
> > find
> > yourself setting the values of properties using complex expressions. For
> > instance,
> > if you need to write a page that asks for Kermit's name, his father's name,
> > and his
> > grandfather's name, you can do one of two things:
> > � Set the properties name, fatherName, and grandfatherName in your action,
> > and then write code that creates three Muppets, sets their names, and
> > reconnects
> > their relationships.
> > � Set the properties kermit.name, kermit.father.name, and
> > kermit.father.father.name, and include a single Muppet object, kermit, in
> > your action.
> > Clearly, the second choice is simple: It involves only one property in your
> > action
> > instead of three, and it doesn't require you to reconstruct the objects. But
> > how?
> > Recall that there is no constructor in Muppet that places stubs for the
> > father property,
> > which means that attempting to set kermit.father.name with a value will
> > result in a NullPointerException.
> > This is where OGNL steps in. It provides a way to swap in a null object with
> > a
> > real object whenever access to a property on a null object is detected. With
> > Web-
> > Work's assistance, OGNL essentially constructs the object graph of the
> > son-fathergrandfather relationship automatically, reducing the code you need
> > to write.
> >
> > On 4/24/06, Geoff Longman <gl...@gmail.com> wrote:
> > >
> > > The ognl expression translates into java calls.
> > >
> > > So client.address.street would translate into
> > >
> > > getClient().getAddress().getStreet()
> > >
> > > if getClient() or getAddress() return null, boom you get an NPE.
> > >
> > > I doubt that if webwork is using OGNL that the behaviour there is any
> > > different from what I have described.
> > >
> > > Geoff
> > >
> > > On 4/24/06, Angelo Luis <an...@gmail.com> wrote:
> > > > I have a Client that have a Adrress and i want to navigate in the object
> > > > graph in that way : client.address.street, without have a null pointer
> > > > exception... how can i do that...
> > > >
> > > > I kwon that i can do that with webwork. is that a way to do in
> > > tapestry???
> > > > Both (tapestry and ww) uses OGNL, so ....
> > > >
> > > > PS; sorry for my english!
> > > >
> > > >
> > >
> > >
> > > --
> > > The Spindle guy. http://spindle.sf.net
> > > Blog: http://jroller.com/page/glongman
> > > Other interests: http://www.squidoo.com/spaceelevator/
> > >
> > > ---------------------------------------------------------------------
> > > To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> > > For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
> > >
> > >
> >
>
>
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Re: Navigate in the object graph in tapestry!!!
Posted by an...@di.uoa.gr.
I remember last year, someone wanted to do the same thing...
and he succeeded by patching ognl.
Looking at the link you provided, it seems that one can simply do
a OgnlRuntime.setNullHandler. Have you tried that?
However, an additional configuration point for this ognl
setting would be nice...
According to
http://jakarta.apache.org/tapestry/tapestry/hivedocs/module/tapestry.ognl.html
we only support custom property accessors.
Please add a bug report for this...
>From Angelo Luis <an...@gmail.com>:
> In webwork if the property is null the ww construct the object, and i think
> that's use OGNL to do this,
> http://www.opensymphony.com/ognl/html/DeveloperGuide/nullHandler.html ...
>
>
> This is the part of WW in Action (Manning) that talk about that... Maybe,
> Tapestry implement htis some day (as soon as possible, hehe)
>
> As you become more familiar with writing WebWork applications, you'll often
> find
> yourself setting the values of properties using complex expressions. For
> instance,
> if you need to write a page that asks for Kermit's name, his father's name,
> and his
> grandfather's name, you can do one of two things:
> � Set the properties name, fatherName, and grandfatherName in your action,
> and then write code that creates three Muppets, sets their names, and
> reconnects
> their relationships.
> � Set the properties kermit.name, kermit.father.name, and
> kermit.father.father.name, and include a single Muppet object, kermit, in
> your action.
> Clearly, the second choice is simple: It involves only one property in your
> action
> instead of three, and it doesn't require you to reconstruct the objects. But
> how?
> Recall that there is no constructor in Muppet that places stubs for the
> father property,
> which means that attempting to set kermit.father.name with a value will
> result in a NullPointerException.
> This is where OGNL steps in. It provides a way to swap in a null object with
> a
> real object whenever access to a property on a null object is detected. With
> Web-
> Work's assistance, OGNL essentially constructs the object graph of the
> son-fathergrandfather relationship automatically, reducing the code you need
> to write.
>
> On 4/24/06, Geoff Longman <gl...@gmail.com> wrote:
> >
> > The ognl expression translates into java calls.
> >
> > So client.address.street would translate into
> >
> > getClient().getAddress().getStreet()
> >
> > if getClient() or getAddress() return null, boom you get an NPE.
> >
> > I doubt that if webwork is using OGNL that the behaviour there is any
> > different from what I have described.
> >
> > Geoff
> >
> > On 4/24/06, Angelo Luis <an...@gmail.com> wrote:
> > > I have a Client that have a Adrress and i want to navigate in the object
> > > graph in that way : client.address.street, without have a null pointer
> > > exception... how can i do that...
> > >
> > > I kwon that i can do that with webwork. is that a way to do in
> > tapestry???
> > > Both (tapestry and ww) uses OGNL, so ....
> > >
> > > PS; sorry for my english!
> > >
> > >
> >
> >
> > --
> > The Spindle guy. http://spindle.sf.net
> > Blog: http://jroller.com/page/glongman
> > Other interests: http://www.squidoo.com/spaceelevator/
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> > For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
> >
> >
>
--
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Re: Navigate in the object graph in tapestry!!!
Posted by Angelo Luis <an...@gmail.com>.
In webwork if the property is null the ww construct the object, and i think
that's use OGNL to do this,
http://www.opensymphony.com/ognl/html/DeveloperGuide/nullHandler.html ...
This is the part of WW in Action (Manning) that talk about that... Maybe,
Tapestry implement htis some day (as soon as possible, hehe)
As you become more familiar with writing WebWork applications, you'll often
find
yourself setting the values of properties using complex expressions. For
instance,
if you need to write a page that asks for Kermit's name, his father's name,
and his
grandfather's name, you can do one of two things:
■ Set the properties name, fatherName, and grandfatherName in your action,
and then write code that creates three Muppets, sets their names, and
reconnects
their relationships.
■ Set the properties kermit.name, kermit.father.name, and
kermit.father.father.name, and include a single Muppet object, kermit, in
your action.
Clearly, the second choice is simple: It involves only one property in your
action
instead of three, and it doesn't require you to reconstruct the objects. But
how?
Recall that there is no constructor in Muppet that places stubs for the
father property,
which means that attempting to set kermit.father.name with a value will
result in a NullPointerException.
This is where OGNL steps in. It provides a way to swap in a null object with
a
real object whenever access to a property on a null object is detected. With
Web-
Work's assistance, OGNL essentially constructs the object graph of the
son-fathergrandfather relationship automatically, reducing the code you need
to write.
On 4/24/06, Geoff Longman <gl...@gmail.com> wrote:
>
> The ognl expression translates into java calls.
>
> So client.address.street would translate into
>
> getClient().getAddress().getStreet()
>
> if getClient() or getAddress() return null, boom you get an NPE.
>
> I doubt that if webwork is using OGNL that the behaviour there is any
> different from what I have described.
>
> Geoff
>
> On 4/24/06, Angelo Luis <an...@gmail.com> wrote:
> > I have a Client that have a Adrress and i want to navigate in the object
> > graph in that way : client.address.street, without have a null pointer
> > exception... how can i do that...
> >
> > I kwon that i can do that with webwork. is that a way to do in
> tapestry???
> > Both (tapestry and ww) uses OGNL, so ....
> >
> > PS; sorry for my english!
> >
> >
>
>
> --
> The Spindle guy. http://spindle.sf.net
> Blog: http://jroller.com/page/glongman
> Other interests: http://www.squidoo.com/spaceelevator/
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
>
>
Re: Navigate in the object graph in tapestry!!!
Posted by Geoff Longman <gl...@gmail.com>.
The ognl expression translates into java calls.
So client.address.street would translate into
getClient().getAddress().getStreet()
if getClient() or getAddress() return null, boom you get an NPE.
I doubt that if webwork is using OGNL that the behaviour there is any
different from what I have described.
Geoff
On 4/24/06, Angelo Luis <an...@gmail.com> wrote:
> I have a Client that have a Adrress and i want to navigate in the object
> graph in that way : client.address.street, without have a null pointer
> exception... how can i do that...
>
> I kwon that i can do that with webwork. is that a way to do in tapestry???
> Both (tapestry and ww) uses OGNL, so ....
>
> PS; sorry for my english!
>
>
--
The Spindle guy. http://spindle.sf.net
Blog: http://jroller.com/page/glongman
Other interests: http://www.squidoo.com/spaceelevator/
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To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
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