At it's simplest, if you have an interface:
    public interface Foo<T> { void setProp(T prop); }

and an implementing class:
    public class Bar implements Foo<String> { void setProp(String prop) { } }

stripes will treat Bar.prop as if it is of type object. This is a direct result of the JDK Introspector returning a PropertyDescriptor that contains a bridge method with the parameter type Object. To fix this it is necessary to identify the appropriate/matching non-bridge method and read type information from there.