Erik Hatcher finally had some time to grok AOP and AspectJ. He got quickly up to speed (as he normally does) and saw a use for it right away.
The one feature that has bothered me about Tapestry is its difference with what happens when validation fails compared to Struts. When validation fails, the listener method is still called in Tapestry, and this requires a bit of code to handle it *in every single listener method*. While I'm still on the fence on whether Tapestry should itself avoid calling a form listener method when validation fails, in the apps I build it is always the case. AspectJ came to my rescue. I created this aspect...
public aspect ValidationAspect {
void around(BasePage page) : execution(void
Home+.listener(IRequestCycle)) && this(page) {
ValidationDelegate delegate = (ValidationDelegate) page.getBeans().getBean("delegate");
System.out.println("aspected: " + delegate);
if (!delegate.getHasErrors()) {
proceed(page);
}
}
}
That piece of code looks for anything that implements Home base class / interface (Home+).
It would be nice to make this generic for anyone using Tapestry as Erik has said, so that it would only be called on org.apache.tapestry.form.Form listeners (via a cflow()).
Nicely done Erik :)
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