title: Thymeleaf, Spring nested backing object is not binding the values on form submit
body: <p>I have a nested object and I'm using it as a model for a form. </p>
  
  <pre><code>public AgeBracketSet implements Serializable{
      private String id;
      private List&lt;AgeBracket&gt;  ageBrackets;
  
    /* Getters and Setters */
  }
  </code></pre>
  
  <p>I have successfully bound all the properties of this object to the form and I can visualize their values when the view state is rendered. Here's a simplified version of how I'm doing it with Thymeleaf. Essentially, I loop through the items of the list and get their attributes.</p>
  
  <pre><code>&lt;form id="bracketForm" role="form" th:action="${flowExecutionUrl}" th:object="${ageBracketSet}" method="post"&gt;
      &lt;input th:id="'bracketSet_'+*{id}" th:field="*{id}" /&gt;
      &lt;th:block th:each="bracket,loop : *{ageBrackets}" th:id="'bracket_'+${bracket.id}"&gt;
          &lt;input th:id="'fromAge_'+${bracket.id}" th:field="*{ageBrackets[__${loop.index}__].fromAge}" /&gt;
          &lt;input th:id="'toAge_'+${bracket.id}"  th:field="*{ageBrackets[__${loop.index}__].toAge}" /&gt;
      &lt;/th:block&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>However, when I make changes in the form and submit it, the model remains unchanged. I have confirmed this by debugging the service that receives the form data. The model does not have the changes made in the form. Am I doing anything wrong here?</p>