if (this.baseItemURLGenerator != null) {
            if (this.baseItemURLGenerator instanceof PublicCloneable) {
                PublicCloneable pc
                        = (PublicCloneable) this.baseItemURLGenerator;
                clone.baseItemURLGenerator = (CategoryURLGenerator) pc.clone();
            }
            else {
                throw new CloneNotSupportedException(
                        "Base item URL generator not cloneable.");