Javascript 使用AJAX和servlet上载多个文件

我尝试了互联网上几乎所有可用的东西，但似乎没有任何效果

我有一个HTML5 filereader代码，它将从客户端目录

var f=$（'#fileUpload'）[0]读取所有文件下一步，我想通过AJAX请求将所有这些文件上传到JavaServlet POST方法。为此，我尝试了以下代码-

var data = new FormData();
        $.each(f, function(key, value)
        {
            data.append(key, value);
        });
postFilesData(data);
//some code..
    function postFilesData(data)
    {
     $.ajax({
        url: 'serv2',
        type: 'POST',
        //enctype: 'multipart/form-data',
        data: data,
        cache: false,
        processData: false, 
        mimetyep: 'multipart/form-data',
        contentType: 'multipart/form-data', 
        success: function(data)
        {
            //success
        },
        error: function(textStatus)
        {
            console.log('ERRORS: ' + textStatus);
        }
        });
    }

servlet代码doPOst方法-

System.out.println("Hi what request:"+ServletFileUpload.isMultipartContent(request));
        System.out.println("hi bro");
    //  awsUpload.uploadData(foldername);
        System.out.println("outside aws");

        DiskFileItemFactory factory = new DiskFileItemFactory();


        ServletFileUpload upload = new ServletFileUpload(factory);

        String uuidValue = "";
        FileItem itemFile = null;

        try {
            // parses the request's content to extract file data
            List formItems = upload.parseRequest(request);
            Iterator iter = formItems.iterator();

            // iterates over form's fields to get UUID Value
            while (iter.hasNext()) {
                FileItem item = (FileItem) iter.next();
                if (item.isFormField()) {

                }
                // processes only fields that are not form fields
                if (!item.isFormField()) {
                    itemFile = item;
                }
            }
        }
            catch (Exception e) {
                // TODO: handle exception
            }

        //System.out.println(path);
    //  response.sendRedirect(path+"/user"+"/home.html");
    //  System.out.println("done");

        if(itemFile==null)
        {
            System.out.println("File Empty Found");
        }
        System.out.println("The File Name is"+itemFile.getName());
}

if (!ServletFileUpload.isMultipartContent(request)) {
            PrintWriter writer = response.getWriter();
            writer.println("Request does not contain upload data");
            writer.flush();
            return;
        }
        // configures upload settings
        DiskFileItemFactory factory = new DiskFileItemFactory();
        factory.setSizeThreshold(THRESHOLD_SIZE);

        ServletFileUpload upload = new ServletFileUpload(factory);
        //upload.setFileSizeMax(MAX_FILE_SIZE);
        //upload.setSizeMax(MAX_REQUEST_SIZE);

        String uuidValue = "";
        FileItem itemFile = null;

        try {
            // parses the request's content to extract file data
            List formItems = upload.parseRequest(request);
            Iterator iter = formItems.iterator();

            // iterates over form's fields to get UUID Value
            while (iter.hasNext()) {
                FileItem item = (FileItem) iter.next();
                if (item.isFormField()) {
                    if (item.getFieldName().equalsIgnoreCase(UUID_STRING)) {
                        uuidValue = item.getString();
                    }
                }
                // processes only fields that are not form fields
                if (!item.isFormField()) {
                    itemFile = item;
                }
            }
            System.out.println("no of items: " + formItems.size());
            System.out.println("FILE NAME IS : "+itemFile.getName());
    }
}

HTML代码：

<form method="POST" enctype="multipart/form-data" >

        <input type="file" class="input-file" name="file[]" id="fileUpload" 
        onchange="fileChanged();" multiple mozdirectory="" 
        webkitdirectory="" directory=""/> <br/>





它打印“找到文件为空”，并在下面一行使用NullPointerException崩溃。我知道它没有得到任何数据。请您指出错误的代码或需要添加的代码缺失
 谢谢你们的回复，伙计们。。！！
要回答@BalusC的问题，是的，它是多部分上传。它进入while循环，但没有从ajax调用传输数据，代码在第-
System.out.println行中断（“文件名为“+itemFile.getName（））因为没有要获取其文件名的项。我得到的唯一例外是控制台“NullPointerException”和UI控制台（在JS中调试时）“500内部服务器错误”
我能够修复代码，并且能够通过AJAX调用将数据传输到Servlet。下面是代码。AJAX调用和servlet代码的代码发生了很大的变化/重构--

AJAX请求--

Servlet代码doPost方法--

我能够打印从UI传递的文件对象中没有一个是正确的。谢谢你们抽出时间，伙计们！！：）
 还有很多东西需要调试和确定，但你没有透露任何细节。先解决这个问题，然后把问题简化成那个问题。例如，它是多部分内容吗？是否输入了while循环？真的没有例外吗？（您的代码有一个空的catch块，它忽略任何异常并继续代码，就像没有发生任何异常一样）。
if (!ServletFileUpload.isMultipartContent(request)) {
            PrintWriter writer = response.getWriter();
            writer.println("Request does not contain upload data");
            writer.flush();
            return;
        }
        // configures upload settings
        DiskFileItemFactory factory = new DiskFileItemFactory();
        factory.setSizeThreshold(THRESHOLD_SIZE);

        ServletFileUpload upload = new ServletFileUpload(factory);
        //upload.setFileSizeMax(MAX_FILE_SIZE);
        //upload.setSizeMax(MAX_REQUEST_SIZE);

        String uuidValue = "";
        FileItem itemFile = null;

        try {
            // parses the request's content to extract file data
            List formItems = upload.parseRequest(request);
            Iterator iter = formItems.iterator();

            // iterates over form's fields to get UUID Value
            while (iter.hasNext()) {
                FileItem item = (FileItem) iter.next();
                if (item.isFormField()) {
                    if (item.getFieldName().equalsIgnoreCase(UUID_STRING)) {
                        uuidValue = item.getString();
                    }
                }
                // processes only fields that are not form fields
                if (!item.isFormField()) {
                    itemFile = item;
                }
            }
            System.out.println("no of items: " + formItems.size());
            System.out.println("FILE NAME IS : "+itemFile.getName());
    }
}