Iterating two list in parallel with thymeleaf

Question

In my current spring-boot project, I have this thymeleaf code:

<th:block th:each="item : ${menu}">
...
              <a th:href="@{/__${menu2}__/listagem}">
                  <i class="icon-asterisk"></i>
                  <span th:utext="${item}"></span>
              </a>
...
<th:block>

where I am trying iterate the two lists (menuand menu2) in a single loop th:each. For menu2 I try this:

${menu2[itemStat.index]}

but I am getting the error:

org.springframework.expression.spel.SpelEvaluationException: EL1012E:(pos 5): Cannot index into a null value

What is the right way to access this second list inside the loop?

UPDATE

• controller:

  @ModelAttribute("menu")
  public List<String> menu() throws Exception {
      return ApplicationClasses.lista_classes_projeto();
  }
  @ModelAttribute("menu2")
  public List<Class<?>> menu2() throws Exception {
      return ApplicationClasses.lista_classes_projeto_2();
  }
  

• ApplicationClasses:

  public static List<String> lista_classes_projeto() throws ClassNotFoundException {
  Locale currentLocale = Locale.getDefault();
      ResourceBundle messages = ResourceBundle.getBundle("messages", currentLocale);
  
  List<String> lista = new ArrayList<String>();
  
  ClassPathScanningCandidateComponentProvider scanner = new ClassPathScanningCandidateComponentProvider(false);
  scanner.addIncludeFilter(new AnnotationTypeFilter(Form.class));
  for (BeanDefinition bd : scanner.findCandidateComponents("com.spring.loja.model")) {
    Class<?> clazz = Class.forName(bd.getBeanClassName());
    lista.add(messages.getString(clazz.getSimpleName()));
  }
  
  return lista;
  }
  
  public static List<Class<?>> lista_classes_projeto_2() throws ClassNotFoundException {
  List<Class<?>> lista = new ArrayList<Class<?>>();
  
  ClassPathScanningCandidateComponentProvider scanner = new ClassPathScanningCandidateComponentProvider(false);
  scanner.addIncludeFilter(new AnnotationTypeFilter(Form.class));
  for (BeanDefinition bd : scanner.findCandidateComponents("com.spring.loja.model")) {
    Class<?> clazz = Class.forName(bd.getBeanClassName());
    lista.add(clazz);
  }
  
  return lista;
  }
  

Answer 1

Not having more details i'm making big assumptions when providing this answer.

<block th:each="item,itemStat : ${menu}">
<span th:text="*{menu2[__${itemStat .index}__].something}"></span>  // assuming its a object that has parameter called somethin
</block>

Your menu 2 list i believe is empty hence the null too.