Re: crazy NPE error, ognl bug?

[Henri Dupre]

More details on this error:
- it happens after redeploying the app on tomcat
- it is a random error, doesn't happen every time
- I have a Introspector listener that flushes the caches in my web.xml
- this is not new, I saw others posts on the list about this, this seems to
be hanging around since tapestry 3. There is even a JIRA entry
http://issues.apache.org/jira/browse/TAPESTRY-408



On 6/12/06, Henri Dupre <[EMAIL PROTECTED]> wrote:

 I have a simple component called "RadioPropertySelection". This component
is somehow a copy paste from the propertyselection code except that it
renders a list in radio buttons.
Somehow one of the parameters "model" gets lost!
I believe my ognl construct is right and refers a constant:

ognl:@[EMAIL PROTECTED] points to
a public static final IPropertySelectionModel = new
StringPropertySelectionModel(...);

My parameters is obtained using annotations:
    @Parameter(required = true)
    public abstract IPropertySelectionModel getModel();

and here is the piece of code from where the NPE comes from:

    protected void renderFormComponent(IMarkupWriter writer, IRequestCycle
cycle)
    {

        IPropertySelectionModel model = getModel();

        if (model == null)
***line 51            throw Tapestry.createRequiredParameterException(this,
"model");


org.apache.tapestry.BindingException  Value for parameter 'model' in
component ListeArticles/$RadioPropertySelection is null, and a non-null
value is required.  binding: ExpressionBinding[ListeArticles @
[EMAIL PROTECTED] _MODEL]  component: [EMAIL PROTECTED]/$RadioPropertySelection]
 location: context:/WEB-INF/catalogue/ListeArticles.html, line 470

  465 <tr> 466 <td width="691" height="23" valign="middle"> 467 <strong>
468 Trier par :  469 </strong> 470 <span jwcid="@RadioPropertySelection"
model="ognl:@[EMAIL PROTECTED]"
submitOnChange="true" value="ognl:classement">  471 D&eacute;signations
472  473 &nbsp;&nbsp;&nbsp;&nbsp; 474 <input type="radio"
name="radiobutton" value="radiobutton" onfocus="this.checked=true;
this.submit()"> 475 Montants
  Stack Trace:

   - org.apache.tapestry.Tapestry.createRequiredParameterException(
   Tapestry.java:643)
   -
   actualis.web.tapestry.components.RadioPropertySelection.renderFormComponent
   (RadioPropertySelection.java:51)
   - org.apache.tapestry.form.AbstractFormComponent.renderComponent(
   AbstractFormComponent.java:122)
   - org.apache.tapestry.AbstractComponent.render(
   AbstractComponent.java:617)


Does this make any sense to anyone? How can a constant become null during
render??

Thanks,

Henri.

--
Thanks,

Henri.