If you remember, 5 months ago I stumbled on a EL limitation on managed beans with generic types (thread with subject "Is JSF incompatible with generics?").
To refresh your memory, the problem is when we have a class like:
public class GenericsTestController<E extends Object> {
private E value;
public E getValue() {
return value;
}
public void setValue(E value) {
this.value = value;
}
}
And we have this class to use as a managed bean (integerTest):
public class IntegerTestController extends GenericsTestController<Integer> {
public String add() {
setValue(getValue()+1);
return null;
}
public String subtract() {
setValue(getValue()-1);
return null;
}
}
This JSF code will not work:
<h:form>
Value:
<h:inputText value="#{integerTest.value}" />
<h:commandButton action="#{integerTest.add}" value="+" />
<h:commandButton action="#{integerTest.subtract}" value="-" />
</h:form>
With this error:
java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
at genericstest.IntegerTestController.add(IntegerTestController.java:18)
I've tried to get in touch with the EL Spec leader (Kin-man Chung) as suggested, but I've got no reply. I've sent a mail to the (empty) UEL mailing list, and I've got no reply.
I've got my own version of EL (based on jboss-el) working even with very complex generic inheritance. However, the changes are in code covered by the spec, more specifically, with section 2.2.7 of the specification:
The provided property will first be coerced to a String. If there is a BeanInfoProperty for this
property and there were no errors retrieving it, the propertyType of the propertyDescriptor is
returned. Otherwise, a PropertyNotFoundException is thrown.
The propertyType of a generic property is Object.class, that gets coerced to String.class, and we get the ClassCastException.
So, what should we do? I'm I the only one that is using generics and JSF?
Thanks,
José Freire
Consulting - Financial Services Industry
Deloitte Consultores, S.A.
Deloitte | Edifício Atrium Saldanha, Praça Duque de Saldanha, 1 - 7º, 1050-094 Lisboa, Portugal
Tel/Direct: +(351) 210 422 500 | Fax: +(351) 210 422 950
jfreire_at_deloitte.pt | www.deloitte.pt
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