Pass a object from Select in Thyemleaf - spring

Question

I have the following class:
public class Person {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "person_id")
private int personId;
#Column(name = "person_name", unique = true)
private String personName;
#Column(name = "gender")
private Gender personGender;
}
Here is Gender as well:
public class Gender{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "gender_id")
private int genderId;
#Column(name = "gender_name", unique = true)
private String genderName;
}
I've assembled a Thymelef dropdown menu when creating a new Person that looks like this:
#RequestMapping(value = ("/newPerson"), method = RequestMethod.GET)
public ModelAndView createPerson() {
ModelAndView model = new ModelAndView();
Person person= new Person ();
model.addObject("person", person);
List<Gender> genders= genderService.getAll();
model.addObject("genders", genders);
model.setViewName("user/newPerson");
return model;
}
(I realize it looks kinda dumb, but it is a simplified version of my code.)
And here is the HTML:
<form class="form-createNew" role="form" method="POST"
th:action="#{/newPerson}" th:object="${person}">
<div class="form-row">
<div class="col">
<div class="form-label-group">
<input type="text" th:field="*{personName}" id="personName" class="form-control" placeholder="Person name">
</div>
</div>
</div>
<div class="form-row">
<div class="col">
<div class="form-label-group">
<select th:field="*{personGender}" class="form-control"
id="personGender" name="personGender">
<option value="" selected disabled hidden>Select gender</option>
<option th:each="gender: ${genders}"
th:value="${gender.genderId}"
th:text="${gender.genderName}"></option>
</select>
</div>
</div>
</div>
<button id="registerBtn" class="btn btn-lg btn-primary btn-block shadow-none text-uppercase" type="submit"> Create </button>
</form>
And finally my question:
What I am receiving at the POST method in the controller for /newPerson is a Person object with the value from the input field, but NULL for the Gender. What is causing that and where am I wrong here? I went through similar questions on SO regarding that issue and also the Thymeleaf Docs/Baeldung and everything looks okay to me.
Any help is appreciated! :)

Answer 1

You are sending for your post controller something like this:
personGender: gernderId
You must do:
personGender.genderId : genderId
For that use in your html:
th:field="*{personGender.genderId}"
instead of
th:field="*{personGender}"
I think it will help you!