迭代兩個列表與thymeleaf

Question

在我目前的春天啓動的項目的同時，我有這樣的thymeleaf代碼：

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

在那裏我想在一個循環th:each迭代兩個列表（menu和menu2）。對於menu2我試試這個：

${menu2[itemStat.index]} 

但我得到的錯誤：

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

什麼是訪問循環內第二個下拉列表的正確方法？

UPDATE

• 控制器：

  @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

由於沒有更多的細節我要做個g提供這個答案時的重要假設。

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

你的菜單2列表我相信是空的，因此也是null。