I wanna convert MultipartFile to required type byte[] but I'm getting an error

Question

I'm working with spring Data-Jpa using spring boot. I have a multipart form to upload file to the database with additional fields such as ( firstName, lastName, email,resume etc.) But I keep getting this error message for converting multipart file into required byte[] type. How can I convert the pdf file from multipart file to byte[] type?

Here is myControllerClass

@RequestMapping(value = "/jobs/applyJob/{id}", method = RequestMethod.POST)
public String handleFormSubmit(@PathVariable Long id, @ModelAttribute @Valid Candidate candidate,
        BindingResult bindingResult, @RequestParam("resume") MultipartFile file,
        RedirectAttributes redirectAttributes) {
    Job job = jobService.findJob(id);
    candidate.setJob(job);
    if (file.isEmpty()) {
        return null;
    }
    try {
        byte[] content  = file.getBytes();
        Path path = Paths.get(UPLOAD_FOLDER + file.getOriginalFilename());
        Files.write(path, content);


    } catch (IOException e) {
        e.printStackTrace();
    }

    if (bindingResult.hasErrors()) {
        return "applyJob";
    }

    redirectAttributes.addFlashAttribute("message", "Job applied !");
    return "redirect:/jobs";
}

My entity :

@Entity
@Table(name = "candidates")
public class Candidate {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotEmpty
    @Column(name = "first_name", length = 50)
    private String firstName;

    @NotEmpty
    @Column(name = "last_name", length = 50)
    private String lastName;

    @NotEmpty
    @Column(name = "email", length = 100)
    private String email;

    @NotEmpty
    @Column(name = "phone", length = 15)
    private String phone;

    @NotEmpty
    @Column(name = "address", length = 255)
    private String address;

    @NotEmpty
    @Column(name = "thoughts_on_job", length = 255)
    private String thoughtsOnJob;

    @NotEmpty
    @Column(name = "resume")
    @Lob
    private byte[] resume;

My error :

Failed to convert property value of type org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile to required type byte[] for property resume; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile to required type byte for property resume[0]: PropertyEditor [org.springframework.beans.propertyeditors.CustomNumberEditor] returned inappropriate value of type org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile

Answer 1

This is a common issue in handling the uploaded file in Spring MVC, which is unable to convert the uploaded file into byte arrays automatically. To make it work, you have to register a custom editor (ByteArrayMultipartFileEditor) in the SimpleFormController’s initBinder() method to guide Spring to convert the uploaded file into byte array.

in your controller use this:

@Override
    protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder)
        throws ServletException {
        
        // Convert multipart object to byte[]
        binder.registerCustomEditor(byte[].class, new ByteArrayMultipartFileEditor());
        
    }

if you are using annotated controller, instead of overriding, use the annotation @InitBinder

you can find more explanation by following this link: https://mkyong.com/spring-mvc/spring-mvc-failed-to-convert-property-value-in-file-upload-form/

i got the answer there and i wanted to share it with u

Answer 2

Make sure you provide enctype="multipart/form-data" in your upload form from front-end application.

Below is a sample example(spring boot with hibernate/jpa) for persisting image data as byte[] (lob/blob) into mysql database:

Controller:

public ResponseEntity<?> uploadFile(@NotBlank @PathVariable String userId,
                                    @RequestParam(value = "profileType", defaultValue = "LOGO", required = false) String profileType,
                                    @RequestParam("avatarFile") MultipartFile avatarFile) {
    return userService.storeFile(user, profileType, avatarFile);
 }

Service:

 @Override
public userImageData storeFile(user user, String profileType, MultipartFile file) {
    log.debug(String.format("Executing < %s.%s#%s()", THIS_CLASS.getPackage().getName(),this.getClass(), new Object() {}.getClass().getEnclosingMethod().getName()));
    if(file != null && !isEmpty(file.getOriginalFilename())){
        String fileName = StringUtils.cleanPath(file.getOriginalFilename());

        try {
            if (fileName.contains("..")) {
                throw new FileStorageException("Sorry! Filename contains invalid path sequence " + fileName);
            }
            userImageData userAvatar = new userImageData();
            Optional<userImageData> userAvatarOp  = imageDataRepository.findByuserImageDatauserEqualsAndImageTypeEquals(user, profileType);


            if(userAvatarOp.isPresent()){
                userAvatar = userAvatarOp.get();
            }

            userAvatar.setuserImageDatauser(user);
            userAvatar.setImageType(profileType);
            userAvatar.setFileName(fileName);
            userAvatar.setFileType(file.getContentType());
            userAvatar.setData(file.getBytes());
            userAvatar.setFileSize(file.getSize());
            userAvatar.setUploadId(UUID.randomUUID().toString());

            return imageDataRepository.save(userAvatar);
        } catch (IOException ex) {
            throw new FileStorageException("Could not store file " + fileName + ". Please try again!", ex);
        }
    }
    log.error("Invalid user image data. Please try again!");
    return null;
}

Pojo:

@Entity
@Table(name = "user_avatar")
public class userImageData {

@Id
@GeneratedValue(generator = "UUID")
@GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
@Column(name = "user_avatar_Id")
private String userImageId;

@ManyToOne
@JoinColumn(name = "user_id")
@JsonIgnore
private user userImageDatauser;

private String imageType;
private String fileName;
private String fileType;
private Long fileSize;
@Lob
private byte[] data;
@Transient
private String fileAccessUri;

@GeneratedValue(generator = "UUID")
@GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
private String uploadId;

}