Spring Boot - not getting a validation errors - spring

Question

I'm trying to validate the form. Spring correctly validates, but when errors should be returned, it receives an exception:
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'employee' available as request attribute
Add I don't know what is wrong. Could you help me?
Controller:
#RequestMapping(value = "/employee/add",method = RequestMethod.POST)
public String addEmployee(#Valid DTOEmployee dtoEmployee, BindingResult result) {
if (result.hasErrors()) {
return "employee_add";
}
employeeService.save(dtoEmployee);
return "redirect:/employee?add";
}
DTOEmployee:
public class DTOEmployee{
#NotNull
private String name;
#NotNull
private String subname;
#NotNull
private String email;
}
fragments of employee_add:
<form th:action="#{/employee/add}" th:object="${employee}" method="post" class="form-inline justify-content-center">
<div class="input-group my-1">
<input th:field="*{name}" type="text" id="name" class="form-control"
placeholder="Your name"/>
<p th:if="${#fields.hasErrors('name')}" th:errors="*{name}">Name error</p>
<input th:field="*{subname}" type="text" id="name" class="form-control"
placeholder="Your subname"/>
<p th:if="${#fields.hasErrors('subname')}" th:errors="*{name}">Name error</p>
<input th:field="*{email}" type="email" id="email" class="form-control"
placeholder="Your mail"/>
<p th:if="${#fields.hasErrors('email')}" th:errors="*{email}">Name error</p>
</div>
<button type="submit" class="btn btn-primary">Save</button>
</form>
messages.properties:
NotNull.DTOEmployee.name = Name must be not null
NotNull.DTOEmployee.subname= Subname must be not null
NotNull.DTOEmployee.email= Email must be not null

Answer 1

Seems like you are mixing thymeleaf form submission with requests. As stated in the example from spring.io https://spring.io/guides/gs/handling-form-submission/
#PostMapping("/greeting")
public String greetingSubmit(#ModelAttribute Greeting greeting) {
return "result";
}
Seems you are missing #ModelAttribute

Answer 2

Hmmm... I`m added #ModelAttribute [ public String addEmployee(#Valid #ModelAttribute DTOEmployee dtoEmployee, BindingResult result)] and I get the following exception:
Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Error during execution of processor 'org.thymeleaf.spring5.processor.SpringInputGeneralFieldTagProcessor' (template: "employee_add" - line 44, col 44)] with root cause
line 44 in employee_add is:
<input th:field="*{name}" type="text" id="name" class="form-control"
EDIT:
I forgot to add the attribute name in quotes:
public String addEmployee(#Valid #ModelAttribute("employee") DTOEmployee dtoEmployee, BindingResult result)
It`s work :)