从thymeleaf复选框设置java.util.Set的值

Question

I'm creating Spring Boot application. I have class User where I am mapping (ManyToMany) with Role class.

I have role setter in User class as:

public Set<Role> getRoles() {
    return roles;
}

public void setRoles(Set<Role> roles) {
    this.roles = roles;
}

From Controller I use RoleRepository class to get names of all roles. I am iterating it in html and creating checkbox:

<form th:object="${userForm}">
  <!-- userForm is coming from controller: -->
  <!-- model.addAttribute("userForm", new User()); -->
  <div class="checkbox" th:each="role: ${allroles.roleList}">
    <input th:field="*{roles}" type="checkbox" th:value="${role}">
    <input th:field="*{roles}" type="hidden" th:value="${role}">
    <td th:text="${role}"></td>
  </div>
</form>

I want that when I click submit, the selected roles should be sent but it is returning null .

Answer 1

You don't need to add:

 <input th:field="*{roles}" type="hidden" th:value="${role}"/> 

It is already managed by the Thymeleaf engine.

The problem may be related to allroles.roleList . You mentioned that you are getting only the names of the roles and your User requires a list of Role objects. Please make sure that you are putting in the model a list of Role objects.

If you want to use only the names of the roles, you should create another class UserForm with:

public Set<String> getRoles() {
   return roles;
}

public void setRoles(Set<String> roles) {
   this.roles = roles;
}

You should add in the form the endpoint and Http method for clarity. Example:

<form th:object="${userForm}" th:action="@{/user}" method="post">
   <div class="checkbox" th:each="role: ${allRoles}">
    <label th:text="${role.name}"></label>
    <input th:field="*{roles}" type="checkbox" th:value="${role}"/>
   </div>
   <input type="submit"/>
</form>

Please make sure that in your controller you have @ModelAttribute

Example:

@PostMapping("/user")
public String submitUser(@ModelAttribute("userForm") User user) {