why read ony ComponentEventException

[Ken in Nashua]

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>