产品需求：

前端上传个csv 或 excel 文件，文件共4列，验证文件大小，类型，文件名长度，文件内容，如果某行某个单元格数据验证不通过，就把错误信息放到这行第五列，然后把带有错误信息的文件，返回给前端。

    @ApiOperation(value = "上传新增")
    @PostMapping(path = "uploadFile")
    public ResultMsg<?> uploadExcelFile(@RequestParam("file") MultipartFile file) throws IOException {

        if (file.getOriginalFilename().length() > 256) {
            return ResultMsg.failed("文件名超长");
        }

        if (file.getSize() > 3 * 1024 * 1024) {
            return ResultMsg.failed("文件太大");
        }

        String fileType = Optional.ofNullable(file.getOriginalFilename())
                .map(name -> name.substring(name.lastIndexOf(".")))
                .orElse(null);
        if (!".xls".equalsIgnoreCase(fileType) && !".xlsx".equalsIgnoreCase(fileType) && !".csv".equalsIgnoreCase(fileType)) {
            return ResultMsg.failed("仅支持 [xls xlsx csv] 格式");
        }

        StyleOfWritingExcelDTO dto = null;
        try {
            dto = this.validateAndReadExcel(file.getInputStream());
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        if (dto.getHasError()) {

            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            EasyExcel.write(byteArrayOutputStream, StyleOfWritingExcelModel.class)
//                        .excelType(ExcelTypeEnum.XLSX)
                    .sheet("sheet1")
                    .doWrite(dto.getStyleOfWritingExcelModelList());
            String base64Str = Base64.getEncoder().encodeToString(byteArrayOutputStream.toByteArray());
            Map<Object, Object> base64Map = new HashMap<>();
            base64Map.put("errStr", "文件内容不合格");
            base64Map.put("fileData", base64Str);
            return ResultMsg.failed(4001, "文件内容不合格", base64Map);

        }
        if (dto.getStyleOfWritingExcelModelList().isEmpty()) return ResultMsg.failed("文件内容为空");
        saveData(dto.getStyleOfWritingExcelModelList());
        return ResultMsg.success();

    }


private StyleOfWritingExcelDTO validateAndReadExcel(InputStream inputStream) {
        StyleOfWritingExcelDTO result = new StyleOfWritingExcelDTO();
        List<StyleOfWritingExcelModel> dataList = new ArrayList<>();

        EasyExcel.read(inputStream, StyleOfWritingExcelModel.class, new AnalysisEventListener<StyleOfWritingExcelModel>() {
            @Override
            public void invoke(StyleOfWritingExcelModel styleOfWritingExcelModel, AnalysisContext analysisContext) {

                StringBuilder errorInfo = new StringBuilder();

                CategoryEntity firstCategory = null;
                if (StringUtils.isBlank(styleOfWritingExcelModel.getFirstCategoryName())) {
                    errorInfo.append("品类不能为空；");
                } else if (styleOfWritingExcelModel.getFirstCategoryName().length() > 50) {
                    errorInfo.append(String.format("品类名长度超限，限制最大[%d]字符；", 50));
                } else {
                    firstCategory = this.getCategoryCode(styleOfWritingExcelModel.getFirstCategoryName());
                    if (ObjectUtils.isEmpty(firstCategory))
                        errorInfo.append(String.format("品类在库里未找到；"));
                    else
                        styleOfWritingExcelModel.setFirstCategory(firstCategory.getCode());
                }

                CategoryEntity secondCategory = null;
                if (StringUtils.isBlank(styleOfWritingExcelModel.getSecondCategoryName())) {
                    errorInfo.append("二级品类不能为空; ");
                } else if (styleOfWritingExcelModel.getSecondCategoryName().length() > 50) {
                    errorInfo.append(String.format("二级品类名长度超限，限制最大[%d]字符", 50));
                } else {
                    secondCategory = this.getCategoryCode(styleOfWritingExcelModel.getSecondCategoryName());
                    if (ObjectUtils.isEmpty(secondCategory))
                        errorInfo.append(String.format("二级品类在库里未找到；"));
                    else
                        styleOfWritingExcelModel.setSecondCategory(secondCategory.getCode());
                }


                if (ObjectUtils.isNotEmpty(firstCategory) && ObjectUtils.isNotEmpty(secondCategory)) {
                    if (!firstCategory.getCode().equals(secondCategory.getParentCode())) {
                        errorInfo.append(String.format("二级品类 和 品类 不匹配"));
                    }
                }


                if (StringUtils.isBlank(styleOfWritingExcelModel.getContent())) {
                    errorInfo.append("内容不能为空; ");
                } else if (styleOfWritingExcelModel.getContent().length() > 3000) {
                    errorInfo.append(String.format("内容长度超限，限制最大[%d]字符", 3000));
                }

                styleOfWritingExcelModel.setErrorInfo(errorInfo.toString());
                dataList.add(styleOfWritingExcelModel);

                if (!result.getHasError() && StringUtils.isNotBlank(errorInfo.toString())) {
                    result.setHasError(true);
                }
            }

            private CategoryEntity getCategoryCode(String categoryName) {
                List<CategoryEntity> categoryList = categoryService.list(new QueryWrapper<CategoryEntity>().lambda().eq(CategoryEntity::getName, categoryName));
                return categoryList.stream()
                        .findFirst()
                        .orElse(null);
            }

            @Override
            public void doAfterAllAnalysed(AnalysisContext context) {
                // 解析完成后的操作
            }
        }).sheet().doRead();
        result.setStyleOfWritingExcelModelList(dataList);
        return result;
    }

返回：


{
  "code": 4001,
  "message": "文件内容不合格",
  "data": {
    "fileData": "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",
    "errStr": "文件内容不合格"
  },
  "timestamp": 63417752000000
}