Can EL call a nonpublic implementor of a public interface? - jsf

Question

Java:
public class MyBean {
...
public Handler getHandler(){
return new Handler(){
public void handle(ActionEvent e){...}
}
}
...
}
public interface Handler{
void handle(ActionEvent e);
}
xhtml:
<h:commandButton ... actionListener="#{myBean.handler.handle}"/>
I'm in a tomcat 6.0 environment. This is a common pattern in java, but it seems not to work with EL method bindings. I get an exception:
javax.faces.event.MethodExpressionActionListener processAction SEVERE): Received 'java.lang.IllegalAccessException' when invoking action listener '#{myBean.handler.handle}' for component 'j_id115'
javax.faces.event.MethodExpressionActionListener processAction SEVERE): java.lang.IllegalAccessException: Class org.apache.el.parser.AstValue can not access a member of class MyBean$1 with modifiers "public"
...

Answer 1

Yes it can, but you did a few things wrong.
First of all the #handle()-method has to be declared as public, because it is an implementation of the public method of your interface.
public class MyBean {
...
public Handler getHandler(){
return new Handler(){
public void handle(){...}
};
}
}
Second point is, that you are calling the Handler as your actionListener, but what you want is to call the #handle()-method:
<h:commandButton actionListener="#{myBean.handler.handle}"/>
You also should omit the ActionEvent from the method-signature in your interface (and implementation)
public interface Handler {
public void handle();
}

Answer 2

This was more subtle than I thought...
From java, there is no problem calling the public method in the inner class:
MyBean myBean = getMyBean();
Handler handler = myBean.getHandler();
handler.handle(event); // OK
Using reflection, it depends on how it's done. The method can be invoked as declared (1):
Method getHandlerMethod = MyBean.class.getMethod("getHandler");
Method handleMethod = getHandlerMethod.getReturnType().getMethod("handle", ActionEvent.class);
handleMethod.invoke(handler, event); // OK, invoking declared method works
Or it can be invoked as defined in the inner class (2):
Method handleMethod = handler.getClass().getMethod("handle", ActionEvent.class);
handleMethod.invoke(handler, event) // throws IllegalAccessException
Obviously, there's a third option, and it works (3):
Method handleMethod = handler.getClass().getDeclaredMethod("handle", ActionEvent.class);
handleMethod.invoke(handler, event) // OK
Unfortunately, my JSF environment (Tomcat 6.0 with JSF mojarra 1.2 and icefaces 1.8.2) implements approach (2) instead of (3) and therefore my example doesn't work.

Answer 3

It should work if you specify the handle() method as ActionListener e.g.
<h:commandButton ... actionListener="#{myBean.handler.handle}"/>
To specify an implementation class of ActionListener interface you can use the "f:actionListener" tag e.g.
<h:commandButton>
<f:actionListener type="com.bla.SomeActionListenerImplementation" />
</h:commandButton>
But this wouldn't work in your case because your MyBean class doesn't implement the ActionListener interface...