我试图上传excel文件，然后保存到产品数据库，我有用户，产品表，但产品Map用户表。所以我尝试上传时出错了。

Caused by: org.h2.jdbc.JdbcSQLIntegrityConstraintViolationException: NULL not allowed for column "USER_ID"; SQL statement:

因为我需要检查谁上传了文件。测绘是必要的。我不知道应该把Map用户ID的代码放在哪里。

@PostMapping("/api/excel/upload/")
    public ResponseEntity<ResponseMessage> uploadFile(@RequestParam("file") MultipartFile file){
        String message = "";
        if (ExcelHelper.hasExcelFormat(file)){
            try{
                excelService.save(file);
                message = "upload suceed: " + file.getOriginalFilename();
                return ResponseEntity.status(HttpStatus.OK).body(new ResponseMessage(message));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        message = "please upload file";
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(new ResponseMessage(message));

@Service
public class ExcelService {
    @Autowired
    ProductRepository repository;

    public void save(MultipartFile file){
        try{
            List<Product> excelEntities = ExcelHelper.excelToExcelEntity(file.getInputStream());
            repository.saveAll(excelEntities);
        }catch (IOException e){
            throw new RuntimeException("failed" + e.getMessage());
        }

编辑文章##

@EntityScan
@Entity
@ApiModel
public class Product extends BaseEntity {
    @Id
    @GeneratedValue
    @Column(name = "product_id")
    private Long id;

    @JsonIgnore
    @ManyToOne(fetch = FetchType.LAZY,optional = false)
    @JoinColumn(name = "user_id")
    private User user;

我添加了excelentity！

public static List<Product> excelToExcelEntity(InputStream inputStream) {
        try {
            Workbook wb = new XSSFWorkbook(inputStream);
            Sheet sheet = wb.getSheet(SHEET);
            Iterator<Row> rows = sheet.iterator();

            List<Product> entities = new ArrayList<Product>();

            int rowNumber = 0;
            while (rows.hasNext()) {
                Row currentRow = rows.next();

                // skip header
                if (rowNumber == 0) {
                    rowNumber++;
                    continue;
                }
                Iterator<Cell> cellsInRow = currentRow.iterator();

                Product excelEntity = new Product();

                DataFormatter formatter = new DataFormatter();
                int cellIdx = 0;
                while (cellsInRow.hasNext()) {
                    Cell currentCell = cellsInRow.next();