尝试将CSV文件上载到服务器时出现空指针异常

Question

我正在尝试上载一个csv文件到服务器。下面是我的HTML代码：

<form method="post" id="uploadCSV" enctype="multipart/form-data">
    File to upload: <input type="file" id="uploadfile" name="file" accept="text/csv">

 <input type="submit" value="Upload" id="uploadcsv" ng-click="uploadCSV()"> Press here to upload the file!
</form>

还有我的JS：-

 $scope.uploadCSV  = function() 

{

        var fileToLoad = document.getElementById("uploadfile").files[0];

        var csvreporturl = "/api/oel/csv";
        $http.post(csvreporturl, fileToLoad).then(function(response, status) {
           console.log("posted:",response);
        });

  }

@RequestMapping(value = "/api/oel/csv", method = RequestMethod.POST)

 String uploadFileHandler(@RequestBody MultipartFile fileToLoad) throws FileNotFoundException, IOException

{

        String name = fileToLoad.getName();
        if (!fileToLoad.isEmpty()) {
            try {
                byte[] bytes = fileToLoad.getBytes();

                // Creating the directory to store file
                //String rootPath = System.getProperty("catalina.home");
                File dir = new File("../dashboard-0.0.12/oel");
                if (!dir.exists())
                    dir.mkdirs();

                // Create the file on server
                File serverFile = new File(dir.getAbsolutePath()
                        + File.separator + name);
                BufferedOutputStream stream = new BufferedOutputStream(
                        new FileOutputStream(serverFile));

                stream.write(bytes);
                stream.close();



                return "You successfully uploaded file=" + name;
            } catch (Exception e) {
                return "You failed to upload " + name + " => " + e.getMessage();
            }
        } else {
            return "You failed to upload " + name
                    + " because the file was empty.";
        }
    }

我面临以下错误：-

加载资源失败：服务器响应的状态为500(HTTP/1.1 500）

可能未经处理的拒绝：{“data”：{“timestamp”：1510643953084,“status”：500,“error”：“内部服务器错误”,“exception”：“java.lang.NullPointerException”,“message”：“没有可用消息”,“path”：“/api/oel/csv”},“status”：500,“config”：{“method”：“post”,“transformrequest”：[null],“transformresponse”：[null],“jsonpcallbackParam”：“callback”,“url”：“

谁能帮帮忙吗？

谢谢

Answer 1

我建议使用以下方法：Apache Commons FileUpload

if (ServletFileUpload.isMultipartContent(request)) {
    FileItemFactory factoryItem = new DiskFileItemFactory();
    ServletFileUpload uploadFile = new ServletFileUpload(factoryItem);

    try {
        List items = uploadFile.parseRequest(request);
        Iterator iterator = items.iterator();
        while (iterator.hasNext()) {
            FileItem item = (FileItem) iterator.next();

            if (!item.isFormField()) {
                String fileName = item.getName();

                String root = getServletContext().getRealPath("/");
                File path = new File(root + "/uploads");
                if (!path.exists()) {
                    boolean status = path.mkdirs();
                }

                File uploadedFile = new File(path + "/" + fileName);
                System.out.println(uploadedFile.getAbsolutePath());
                item.write(uploadedFile);
            }
        }
    } catch (FileUploadException ex) {
        ex.printStackTrace();
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}