Thymeleaf - How to send an object (with child object) from form back to the Controller

Question

I'am trying to "send" a "complex" object from a thymeleaf form back to the controller. I found this minimal example (Send datas from html to controller in Thymeleaf?), which does basically the same thing (Works perfectly). The only difference is, that their object has a String attribute instead of an other object.

But once I replace the String Attribute with the bar object, the bar object is always null, when submitting the form. Is submitting nested objects even possible?

Objects

public class Foo {
    private Bar bar;

    public Bar getBar() {
        return bar;
    }

    public void setBar(Bar bar) {
        this.bar = bar;
    }
}

public class Bar {

    private String id;

    public Bar(String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
}

Controller

@RequestMapping(value = "/showForm", method= RequestMethod.GET)
public String showForm(Model model) {
    Foo foo = new Foo();
    foo.setBar(new Bar("test"));
    model.addAttribute("foo", foo);
    return Pages.TEST;
}

@RequestMapping(value = "/processForm", method=RequestMethod.POST)
public String processForm(@ModelAttribute(value="foo") Foo foo) {
    ...
    return Pages.TEST;
}

HTML

<form action="#" th:action="@{/processForm}" th:object="${foo}" method="post">
    <input type="text" th:field="*{bar}"/>
    <input type="submit"/>
</form>

Answer 1

You have to bind your input text to id field of bar object.

<form action="#" th:action="@{/processForm}" th:object="${foo}" method="post">
    <input type="text" th:field="*{bar.id}"/>
    <input type="submit"/>
</form>