JSF & EL Specification (Resend)

[Jose Freire]

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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@... | www.deloitte.pt

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