code: public void setViewClass(final Class<? extends ThymeleafReactiveView> viewClass) {
          if (viewClass == null || !ThymeleafReactiveView.class.isAssignableFrom(viewClass)) {
              throw new IllegalArgumentException(
                      "Given view class [" + (viewClass != null ? viewClass.getName() : null) +
                      "] is not of type [" + ThymeleafReactiveView.class.getName() + "]");
          }
          this.viewClass = viewClass;
      }
docs: <p>
  Set the view class that should be used to create views. This must be a subclass
  of {@link ThymeleafReactiveView}.
  </p>
  
  @param viewClass class that is assignable to the required view class
  (by default, ThymeleafReactiveView).