Thymeleaf中有没有一种方法可以验证bean的对象属性中的属性？考虑我们确实有一个Departement类，如下所示：

public class Departement {
   @Id
   @GeneratedValue(strategy=GenerationType.IDENTITY)
   private Long idDept;

   @NotEmpty
   private String name;
}

还有另一个Employee类，如下

public class Employee{
  @Id
  @GeneratedValue(strategy=GenerationType.IDENTITY)
  private Long idEmp;

  @NotEmpty
  @Size(min = 5, message="At least five characters needed")
  private String employeeName;

  @NotNull
  private Departement departement;
}

上面的代码在员工表单中使用thymeleaf，由于注释，只有’employeeName’会在spring之前得到验证。让我们在这里看一下

@GetMapping( value = "/emp" )
public String save(Model model){
  Employee emp = new Employee();
  emp.setDepartement(new Departement());
  model.addAttribute('employee', emp);
  return 'view';
}
//------------- Form in PostMapping
@PostMapping( value = "/save", @Valid Emp emp, BindingResult bindingResult )
public String savePost(Model model){
if( ! bindingResult.hasErrors() )
    {
 /* Even if departement has not been choosen, my code always goes here 
and print "Form Ok. Departement : 0" instead of reaching the 'else' block, but if departement choosen, 
it prints the correct value of departemnt 
*/
      System.out.println( "Form Ok.\n Departement : " + emp.getDepartement().getIdDept() );
  }else{
           System.out.println( "Missing attributes." );
  }

  return 'view';
}

这是员工表格

 <form th:action="@{save}" th:object="${emp}" th:method="POST" >
  <span th:if="${#fields.hasErrors('employeeName') }"th:errors="*{employeeName}"></span>
    <input th:field="*{employeeName}" th:value="${employeeName}" />
//--------
   <div th:object="${emp.departement}">
      <span th:if="${#fields.hasErrors('idDept') }"th:errors="*{idDept}"></span>
      <input th:field="*{idDept}" th:value="${idDept}" />
   </div>
</form>

这是我的问题：如何在不使用emplpoyee表单中的javacript的情况下如何验证员工部门标识符（idDept字段）？

注意：我不使用drowpdownlist来显示部门信息，而是希望使用带有所选部门ID的自动完成字段和隐藏字段。