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Posted to users@tapestry.apache.org by Ken in Nashua <kc...@live.com> on 2011/09/18 22:39:21 UTC
why read ony ComponentEventException
Folks,
I have a page feeding read/write property
Home.JAVA
@Property(read = true, write = true) // no getter/setter needed
@Persist("session")
private int itemsPerPage;
to a component parameter
Gallery.JAVA
@Property(read = true, write = true)
@Parameter(required = true, cache = true, defaultPrefix = "50")
private int itemsPerPage;
@BeginRender
public void beginRender()
{
//itemsPerPage = 50;
//tableColumns = 3;
}
org.apache.tapestry5.runtime.ComponentEventExceptionFailure
writing parameter 'value' of component
Home:gallerywidget.itemsperpageselect: Failure writing parameter
'itemsPerPage' of component Home:gallerywidget: Binding
org.apache.tapestry5.internal.services.AttributeExpansionBinding@3e963f38
is read-only.
here are some sources... to possbly indicate the issue but I cannot spot why.
Any ideas ? I would think that the annotations provided are sufficient? Also if I try to set a value to this parameter within the component I receive the same thing...
HOME.TML
...
<t:form t:id="galleryForm" t:name="galleryForm" clientValidation="true">
<t:errors/>
<t:Gallery t:id="GalleryWidget"
collection="${collection}"
itemsPerPage="${itemsPerPage}"
tableColumns="${tableColumns}"
cursor="${cursor}"
/>
</t:form>
</t:layout>
Re: why read ony ComponentEventException
Posted by Bob Harner <bo...@gmail.com>.
This is a frequently-occurring user mistake, especially by developers
new to tapestry. And sometimes the error message is even more
misleading:
org.apache.tapestry5.ioc.util.UnknownValueException: "Could not
find a coercion from type java.lang.String to type com.example.Foo"
I wonder if there's something that can be done to help, like making
the exception message more verbose about the common causes, or maybe
emitting a warning whenever ${...} is used in a component parameter in
a tml file and that parameter has a default binding prefix of "prop:"
or "var:"
On Sun, Sep 18, 2011 at 5:44 PM, Howard Lewis Ship <hl...@gmail.com> wrote:
> ${...} doesn't do what you think it does. It specifically extracts
> the expression and converts it to a String, and the expression is
> read-only.
>
> Bind it like this:
>
> itemsPerPage="itemsPerPage"
>
> this binds the component parameter field directly to the containing
> page's property, so it's read/write.
>
> The use of ${...} was intended for attributes ordinary
> (non-component) elements.
>
> On Sun, Sep 18, 2011 at 1:39 PM, Ken in Nashua <kc...@live.com> wrote:
>>
>> Folks,
>>
>> I have a page feeding read/write property
>>
>> Home.JAVA
>> @Property(read = true, write = true) // no getter/setter needed
>> @Persist("session")
>> private int itemsPerPage;
>>
>> to a component parameter
>>
>> Gallery.JAVA
>> @Property(read = true, write = true)
>> @Parameter(required = true, cache = true, defaultPrefix = "50")
>> private int itemsPerPage;
>>
>> @BeginRender
>>
>> public void beginRender()
>>
>> {
>>
>> //itemsPerPage = 50;
>>
>> //tableColumns = 3;
>>
>> }
>>
>> org.apache.tapestry5.runtime.ComponentEventExceptionFailure
>> writing parameter 'value' of component
>> Home:gallerywidget.itemsperpageselect: Failure writing parameter
>> 'itemsPerPage' of component Home:gallerywidget: Binding
>> org.apache.tapestry5.internal.services.AttributeExpansionBinding@3e963f38
>> is read-only.
>>
>> here are some sources... to possbly indicate the issue but I cannot spot why.
>>
>> Any ideas ? I would think that the annotations provided are sufficient? Also if I try to set a value to this parameter within the component I receive the same thing...
>>
>>
>> HOME.TML
>> ...
>> <t:form t:id="galleryForm" t:name="galleryForm" clientValidation="true">
>> <t:errors/>
>>
>> <t:Gallery t:id="GalleryWidget"
>> collection="${collection}"
>> itemsPerPage="${itemsPerPage}"
>> tableColumns="${tableColumns}"
>> cursor="${cursor}"
>> />
>> </t:form>
>>
>> </t:layout>
>>
>>
>>
>
>
>
> --
> Howard M. Lewis Ship
>
> Creator of Apache Tapestry
>
> The source for Tapestry training, mentoring and support. Contact me to
> learn how I can get you up and productive in Tapestry fast!
>
> (971) 678-5210
> http://howardlewisship.com
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tapestry.apache.org
> For additional commands, e-mail: users-help@tapestry.apache.org
>
>
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Re: why read ony ComponentEventException
Posted by Howard Lewis Ship <hl...@gmail.com>.
${...} doesn't do what you think it does. It specifically extracts
the expression and converts it to a String, and the expression is
read-only.
Bind it like this:
itemsPerPage="itemsPerPage"
this binds the component parameter field directly to the containing
page's property, so it's read/write.
The use of ${...} was intended for attributes ordinary
(non-component) elements.
On Sun, Sep 18, 2011 at 1:39 PM, Ken in Nashua <kc...@live.com> wrote:
>
> Folks,
>
> I have a page feeding read/write property
>
> Home.JAVA
> @Property(read = true, write = true) // no getter/setter needed
> @Persist("session")
> private int itemsPerPage;
>
> to a component parameter
>
> Gallery.JAVA
> @Property(read = true, write = true)
> @Parameter(required = true, cache = true, defaultPrefix = "50")
> private int itemsPerPage;
>
> @BeginRender
>
> public void beginRender()
>
> {
>
> //itemsPerPage = 50;
>
> //tableColumns = 3;
>
> }
>
> org.apache.tapestry5.runtime.ComponentEventExceptionFailure
> writing parameter 'value' of component
> Home:gallerywidget.itemsperpageselect: Failure writing parameter
> 'itemsPerPage' of component Home:gallerywidget: Binding
> org.apache.tapestry5.internal.services.AttributeExpansionBinding@3e963f38
> is read-only.
>
> here are some sources... to possbly indicate the issue but I cannot spot why.
>
> Any ideas ? I would think that the annotations provided are sufficient? Also if I try to set a value to this parameter within the component I receive the same thing...
>
>
> HOME.TML
> ...
> <t:form t:id="galleryForm" t:name="galleryForm" clientValidation="true">
> <t:errors/>
>
> <t:Gallery t:id="GalleryWidget"
> collection="${collection}"
> itemsPerPage="${itemsPerPage}"
> tableColumns="${tableColumns}"
> cursor="${cursor}"
> />
> </t:form>
>
> </t:layout>
>
>
>
--
Howard M. Lewis Ship
Creator of Apache Tapestry
The source for Tapestry training, mentoring and support. Contact me to
learn how I can get you up and productive in Tapestry fast!
(971) 678-5210
http://howardlewisship.com
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tapestry.apache.org
For additional commands, e-mail: users-help@tapestry.apache.org
RE: why read ony ComponentEventException
Posted by Ken in Nashua <kc...@live.com>.
Thanks Howard... i wondered if this one would get your attention and glad I can move onward.
maybe i am getting old in my age but I got 5 years of hard C, 10 years of C++, 12 years of JAVA and a boat load of front end to back end...
conceptual expression parsing and de-referencing caught me up a bit I guess...
and I have thought recently (as I have in the past with tap3 and tap4)... why does tapestry have to be so hard... but I think it's just me
maybe I am asking too much for these semantics should be flagged too... and articulated for the developer
anyway... thanks... in the end tapestry is worth it and I could not think of developing with anything else as extensible and flexible
- cheers
From: kcolassi@live.com
To: users@tapestry.apache.org
Subject: why read ony ComponentEventException
Date: Sun, 18 Sep 2011 16:39:21 -0400
Folks,
I have a page feeding read/write property
Home.JAVA
@Property(read = true, write = true) // no getter/setter needed
@Persist("session")
private int itemsPerPage;
to a component parameter
Gallery.JAVA
@Property(read = true, write = true)
@Parameter(required = true, cache = true, defaultPrefix = "50")
private int itemsPerPage;
@BeginRender
public void beginRender()
{
//itemsPerPage = 50;
//tableColumns = 3;
}
org.apache.tapestry5.runtime.ComponentEventExceptionFailure
writing parameter 'value' of component
Home:gallerywidget.itemsperpageselect: Failure writing parameter
'itemsPerPage' of component Home:gallerywidget: Binding
org.apache.tapestry5.internal.services.AttributeExpansionBinding@3e963f38
is read-only.
here are some sources... to possbly indicate the issue but I cannot spot why.
Any ideas ? I would think that the annotations provided are sufficient? Also if I try to set a value to this parameter within the component I receive the same thing...
HOME.TML
...
<t:form t:id="galleryForm" t:name="galleryForm" clientValidation="true">
<t:errors/>
<t:Gallery t:id="GalleryWidget"
collection="${collection}"
itemsPerPage="${itemsPerPage}"
tableColumns="${tableColumns}"
cursor="${cursor}"
/>
</t:form>
</t:layout>