JSF & EL Specification

From: Freire, Jose Luis \(PT - Lisbon\) <"Freire,>
Date: 4 Nov 2009 11:31:13 +0000

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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


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() {


              return null;


       public String subtract() {


              return null;




This JSF code will not work:



       <h:inputText value="#{integerTest.value}" />

       <h:commandButton action="#{integerTest.add}" value="+" />

       <h:commandButton action="#{integerTest.subtract}" value="-" />



With this error:

java.lang.ClassCastException: java.lang.String cannot be cast to




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?




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 |

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