在Tapestry 5.3中链接多个选择组件（Ajax更新）

I’m using tapestry 5.3.7, and I want to use Ajax chaining select form elements : If I choose one option in a select element, another select appear to choose another element based on your first choice. I try a sample in the tapestry doc, and adapted for my project. Despite the fact that my custom code is very close to the sample, I always have the following error :I’m using tapestry 5.3.7, and I want to use Aja