无法将Excel文件上传到@RestController

Question

尝试从一个html字段中上传一个excel文件以及一些其他信息，并将其存储到一个对象中，该对象将存储在序列化列表中。当前，网页响应输入，但是当我尝试按上载按钮时，它将解析为else语句“ failed”，例外消息为“ null”。

在我们切换到Thymeleaf之前，html只是临时的。

以下代码：

@MultipartConfig
@RestController
@RequestMapping(value = "/Teacher", produces = "text/html;charset=UTF-8")
public class Teacher {
    TestController testcont;

    @GetMapping("")
    @ResponseBody

    public String homePage(@RequestParam(value = "file", required = false) String name, HttpServletRequest request,
            HttpServletResponse response){

        StringBuilder sb = new StringBuilder();


        sb.append("<p> <a href='/Teacher/NewTest'>New Test upload</a></p>\n"
                + "<p><a href='/SelectTest'>Select Test File</a> <button type='button'>Send Test</button></p>"
                + "\n \n \n"
                + "<p><a>Current Test for students:</a>\n <a href='/getCurrentTest'></a></p>"
                );

        return sb.toString();
    }

    @PostMapping
    @RequestMapping("/NewTest")
    @ResponseBody
    public String newTestUpload(HttpServletRequest request, HttpServletResponse response){
        StringBuilder sb = new StringBuilder();

        if(!request.getParameterNames().hasMoreElements()){
            sb.append("<p><form action='' method='post' enctype='multipart/form-data'>"
                    + "<label>Enter file</label><input type='file' name='file'>"

                    + "<button type='submit'>Upload</button></p>"

                    + "<p><form action='/testName'>Test Name: <input type='text' name='name' value=''></p>"

                    + "<p><form action='/addInfo'>Comment: <input type='text' comment='comment' value=''></p>"

                    + "<p>Answer 1: <input type='text' Answer='answer1' value=''></p>"

                    + "<p>Answer 2: <input type='text' Answer='answer2' value=''></p>"

                    + "</form>"

                    + "<a href='/Teacher'>Back</a>\n"
                    );
            return sb.toString();
        }
        else if( request.getParameter("name") != ""
                && request.getParameter("comment") != "" && request.getParameter("answer1") != ""
                && request.getParameter("answer2") != ""){

            try{
                // Upload happens here
                Part filePart = request.getPart("file");
                String fileName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString();
                InputStream fileContent = filePart.getInputStream();

                File testExcel = new File(fileName);
                testExcel.createNewFile();

                Files.copy(fileContent, Paths.get(testExcel.getName()), StandardCopyOption.REPLACE_EXISTING);


                double ans1 = Double.parseDouble(request.getParameter("answer1"));
                double ans2 = Double.parseDouble(request.getParameter("answer2"));

                Test test = new Test(testExcel, request.getParameter("name"), 
                                    request.getParameter("comment"), ans1, ans2);

                testcont.addTest(test);

                sb.append("New test uploaded!<br/>\n<a href='/Teacher'>Back</a>\n");
                return sb.toString();


            } catch (Exception e){
                sb.append("<h1>Couldnt insert test</h1>\n"
                        + e.getMessage());
                response.setStatus(HttpServletResponse.SC_OK);
                return sb.toString();
            }

        }
        else{
            sb.append("failed<br/>\n<a href='/Teacher/NewTest'>Back</a>\n");
            response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
            return sb.toString();
        }

    }

}