滿簡單的，多包一層就可以處理掉。

The file specified in default_filename should be in given static path. So if you move error.htmlto assets/js directory, than navigate to /js/ you will see content of error.html.

Basically this functionality is a helper with limited usecase (imho). More at https://stackoverflow.com/a/27891339/681044

Custom error pages

Every request handler handles/renders errors in write_error function. This is the recommended way to create custom error pages:

class MyStaticFileHandler(tornado.web.StaticFileHandler):

    def write_error(self, status_code, *args, **kwargs):
        # custom 404 page
        if
 
 status_code in [404]:
            self.render('templates/error.html')
        else:
            super().write_error(status_code, *args, **kwargs)