前端js

let formData = new FormData($('#formId')[0]);
// https://developer.mozilla.org/zh-CN/docs/Web/API/FormData
// void append(DOMString name, Blob value, optional DOMString filename);
formData.append('files', file, file.name);
$.ajax({
        cache: true,
        type: "POST",
        url: "/app/goods/save",
        data: formData,//
        async: false,
        processData:false,
        contentType: false,
        error: function (request) {
            parent.layer.alert("Connection error");
        },
        success: function (data) {
            if (data.code == 0) {
                parent.layer.msg("操作成功");
                parent.reLoad();
                var index = parent.layer.getFrameIndex(window.name); // 获取窗口索引
                parent.layer.close(index);

            } else {
                parent.layer.alert(data.msg)
            }

        }
    });

Ajax 使用 FormData做为data的参数时 出现Illegal invocation

processData用于对data参数进行序列化处理，默认值是true。默认情况下发送的数据将被转换为对象，如果不希望把File转换，需要设置为false

        processData:false,
        contentType: false

后台

    private MultipartFile[] files;

   MultipartFile[] files = goods.getFiles();
        if (!ObjectUtils.isEmpty(files)) {
            Arrays.asList(files).forEach(file -> {
                UploadFileResponse fileResponse = fileStorageService.uploadFileResponse(file);
                String filePath = fileResponse.getFilePath();
                logger.debug("filePath: {}", filePath);
                AppImage appImage = new AppImage();
                appImage.setId(IDGenerate.id());
                appImage.setPath(filePath);
                appImage.setCreatedAt(new Date());
                appImage.setFid(id);
                imageService.save(appImage);
            });
        }

    public UploadFileResponse uploadFileResponse(MultipartFile file) {
        String contentType = file.getContentType();
        String originalFilename = file.getOriginalFilename();
        Map<String, String> data = new HashMap<String, String>();
        String fileName = UUID.randomUUID().toString();
        //originalFilename = originalFilename.substring(0, originalFilename.lastIndexOf("."));
        String ext = originalFilename.substring(originalFilename.lastIndexOf("."), originalFilename.length());
        fileName = fileName + ext;
        String filePath = storeFile(file, fileName);
        String fileDownloadUri = ServletUriComponentsBuilder.fromCurrentContextPath()
                .path("system/file/download-file")
                .path(filePath)
                .toUriString();

        UploadFileResponse fileResponse = UploadFileResponse.builder()
                .originFileName(originalFilename)
                .fileType(contentType)
                .size(file.getSize())
                .fileDownloadUri(fileDownloadUri)
                .fileName(fileName)
                .filePath(filePath)
                .build();
        return fileResponse;
    }