If you have a Base class:

public abstract BaseVM<T extends MyDomain> {

@Command("save")
public save(@BindingParam("item")  T model){
//do base func
myrepo.save(model)
}
}

public ConcreteVM extends BaseVM<ConcreteModel>{

@Override
@Command("save")
public save(@BindingParam("item")  T model){
//do additional fun
super.save(model)
}
}

The BinderImpl will return an exception throw new UiException("there are more than one "+... because clz.getMethods return two methods with same name but different params, one for MyDomain and once for ConcreteModel.

This only happen in java 1.8 not in java 1.7 or minor. I think is due to the reflection optimization in java 8.