Varargs in thymeleaf @ModelAttribute?

Question

I want to pass multiple variable parameters (including none) for a @ModelAttribute evaluation from html thymeleaf page to a method:

//provide 0 or X params
@ModelAttribute("url")
public String url(String... params) {
    return "generatedurl";
}

The following thymeleaf statements should be possible:

th:href="@{${url()}"
th:href="@{${url('page')}}"
th:href="@{${url('page', 'sort')}}"

But it does not work. Why?

Answer 1

As a workaround: add the enclosing class as a model parameter, and call the method on this param from thymeleaf:

@Controller
public class PageController {
    @GetMapping
    public String persons(Model model) {
        model.addAttribute("util", this);
        return "persons";
    }

    public String url(String... params) {
        //evaluate...
        return "generatedurl";
    }
}

It's then possible to access the methods as normal:

th:href="@{${url()}"
th:href="@{${url('page')}}"
th:href="@{${url('page', 'sort')}}"

Only drawback is of course having to add the class to the model explicit.

Another choice would be to initialize the model with the parameter permutations that I need. But that's less flexible:

@ModelAttribute
public void init(Model model) {
    model.addAttribute("plainUrl", ...);
    model.addAttribute("pageUrl", ...);
    model.addAttribute("pageSizeUrl", ...);
}