Java Reflection: create new istance of interface give java.lang.ClassCastException

I've an EAR project structure:

EAR

• TestDependency.jar

  • MyInterface.class;

• TestEJBModule.jar

  • ExternalObject.class (implements MyInterface);

• TestWar

  • SingletonBean
  • MyTestClass (implements MyInterface);

In Singleton bean I need to instantiate ExternalObject class dinamically using the class name, but i get

Caused by: javax.ejb.EJBException: java.lang.ClassCastException: com.bsssrl.testejbmodule.ExternalObject cannot be cast to com.bsssrl.MyInterface

The code is:

    Class localclass = Class.forName("com.bsssrl.test.testwar.MyTestClass");
    Object olocal = localclass.newInstance();
    MyInterface local = (MyInterface) olocal;
    LOG.log(Level.INFO, "Test local.getString()   : {0}",local.getString());
    LOG.log(Level.INFO, "Test local.getAlfa()     : {0}",local.getAlfa());


Class exclass = Class.forName("com.bsssrl.testejbmodule.ExternalObject");
Object oex = exclass.newInstance();
if(MyInterface.class.isAssignableFrom(exclass)){
   MyInterface extern = (MyInterface) oex;
   LOG.log(Level.INFO, "Test extern.getString()  : {0}",extern.getString());
   LOG.log(Level.INFO, "Test extern.getAlfa()    : {0}",extern.getAlfa());
}else{
       LOG.log(Level.SEVERE, "Class {0} not implement MyInterface",exclass);
}

The class is :

public class ExternalObject implements MyInterface{

public Alfa alfa ;

@Override
public String getString() {
    return "from external object in EJB module";
}

@Override
public Alfa getAlfa() {
    return alfa;
}

@Override
public void setAlfa(Alfa a) {
    this.alfa = a;
}

}

The first piece of code works, but the second launch ClassCastException; I suppose I have a problem with classloader.

How can I solve it?

PS : I use wildfly-9.0.2.Final