thymeleaf利用th:each循环Map中的List（Map嵌套循环）

    后端传送一个带List的Map参数返回前台，当使用thymeleaf的th:each tag进行嵌套输出时发现内循环无法正确获取到数据。
后台传输对象:

@RequestMapping
    public ModelAndView show(HttpServletRequest req, HttpServletResponse resp, Model model){

        Map<String,Object> file = new HashMap<>();

        List<FileInfo> AA = Arrays
                .asList(new FileInfo("A1CLASS","A1ID","A1PATH","A1NAME"),
                        new FileInfo("A2CLASS","A2ID","A2PATH","A2NAME"),
                        new FileInfo("A3CLASS","A3ID","A3PATH","A3NAME"));

        List<FileInfo> BB = Arrays
                .asList(new FileInfo("B1CLASS","B1ID","B1PATH","B1NAME"),
                        new FileInfo("B2CLASS","B2ID","B2PATH","B2NAME"),
                        new FileInfo("B3CLASS","B3ID","B3PATH","B3NAME"));


        file.put("AA",AA);
        file.put("BB",BB);


        ModelAndView modelAndView = new ModelAndView("ia11/ia1101/ia1101");
        model.addAttribute("file",file);
        model.addAttribute("test","test");
        return modelAndView;
    }

然后在前端使用

标签查看输出内容。
具体HTML代码:

<div id="outDiv" th:each="map:${file}">
    <div class="form-group">
        <label id="lable" class="col-md-2">EACHlabel>
        <div id="document" class="col-md-10">
            <div th:text="${map}">div>

            //in this time the th:each tag is useful

            <div th:each="oneFile:${map}">
                <div th:text="${oneFile}">div>

                // but in this time the th:each tag can't loop the FileInfo object in the AA

                <input type="hidden" name="filesData_CLASS" th:value="${oneFile.fileClass}">
                <input type="hidden" name="filesData_FILE_ID" th:value="${oneFile.fileId}">
                <input type="hidden" name="filesData_PATH" th:value="${oneFile.filePath}">
                <div class="input-group">
                    <input type="text" class="form-control" readonly name="fileChoose_text" th:value="${oneFile.fileName}">
                    <span class="input-group-btn">
                       <button type="button" name="fileChoose_btn" class="btn btn-default btn-flat" style="width:80px;height:34px;">选择button>
                   span>
                div>
            div>
        div>
    div>
div>

在第一个each的时候是可以正常运作的，但是第二个each就能循环了。
在网上用各种姿势搜索都没找到结果，于是我去官方的github上提问了。
官方的回答如下：

When using th:each over Maps, then the value being iterated over is a java.util.Map.Entry type, so when doing your second th:each you need to extract the lists out of the map entry’s value property. So I think something like this will work:

还给出了例子：

  

    
    ...
  

大致意思是 在使用th:each循环map时，他迭代的是Map.Entry所以在第二个循环的时候其实是map的一对键值对，不是只有值得一个List，所以我们需要获取键值对的值，对于值去进行循环。