i’m working on a web application with angular and springboot where i can upload files and store them in the app , i did work on sending mails through my web app but im having trouble fetching the file from the already uploaded and stored files . also the document has to be encrypted while being sent, i’m still a beginner and i did a lot of research and tried a bunch of solutions but nothing works.

package project.service;


import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;
import project.exceptions.FileStorageException;
import project.models.FileUploadEntity;
import project.repository.FileUploadRepository;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.util.Objects;

@Service("FileUploadService")
public class FileUploadService {
    private final FileUploadRepository fileUploadRepository;

    private Path uploadLocation;


    @Autowired
    public FileUploadService(FileUploadRepository fileUploadRepository, Environment environment) {
        this.fileUploadRepository = fileUploadRepository;
        String uploadDir = environment.getProperty("file.upload.dir");
        if (uploadDir == null) {
            throw new IllegalArgumentException("File upload directory is not configured");
        }
        this.uploadLocation = Paths.get(uploadDir).toAbsolutePath().normalize();
        try {
            Files.createDirectories(this.uploadLocation);
        } catch (Exception ex) {
            throw new FileStorageException("Could not create directory", ex);
        }
    }

    public FileUploadEntity uploadFile(String ownedBy, String description, MultipartFile file) throws IOException {
        String originalFileName = StringUtils.cleanPath(Objects.requireNonNull(file.getOriginalFilename()));
        Path targetLocation = this.uploadLocation.resolve(originalFileName);
        Files.copy(file.getInputStream(), targetLocation, StandardCopyOption.REPLACE_EXISTING);
        FileUploadEntity theFile = new FileUploadEntity();
        theFile.setOwnedBy(ownedBy);
        theFile.setDescription(description);
        theFile.setType(file.getContentType());
        theFile.setName(originalFileName);
        theFile.setFile(file.getBytes());
        theFile.setUploadDir(String.valueOf(this.uploadLocation));
        return fileUploadRepository.save(theFile);


    }

    public String deleteFileById(Long fileId) throws FileNotFoundException {
     
        FileUploadEntity fileToDelete = fileUploadRepository.findById(fileId)
                .orElseThrow(() -> new FileNotFoundException("File with ID " + fileId + " not found"));

    
        Path filePath = uploadLocation.resolve(fileToDelete.getName());

        try {
           
            Files.deleteIfExists(filePath);

           
            fileUploadRepository.delete(fileToDelete);

            return "File with ID " + fileId + " deleted successfully";

        } catch (IOException e) {
         
            if (e instanceof FileNotFoundException) {
               
                throw new FileNotFoundException("File with ID " + fileId + " not found at specified path.");
            } else {
                throw new FileStorageException("Failed to delete file", e);
            }
        }
    }
}

this is my file upload service

package project.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

import javax.mail.internet.MimeMessage;

@Service
public class MailServiceImpl  implements MailService.EmailService{
    @Autowired
    private JavaMailSender javaMailSender;

    
    @Value("${spring.mail.username}")
    private String from;

    @Override
    public String sendMail(MultipartFile[] file, String to, String[] cc, String subject, String body) {
        try {
            MimeMessage mimeMessage = javaMailSender.createMimeMessage();
            MimeMessageHelper mimeMessageHelper = new MimeMessageHelper(mimeMessage, true);

        
            mimeMessageHelper.setFrom(from);

            mimeMessageHelper.setTo(to);
            mimeMessageHelper.setCc(cc);
            mimeMessageHelper.setSubject(subject);
            mimeMessageHelper.setText(body);

            for (int i = 0; i < file.length; i++) {
                mimeMessageHelper.addAttachment(
                        file[i].getOriginalFilename(),
                        new ByteArrayResource(file[i].getBytes()));
            }

            javaMailSender.send(mimeMessage);
            return "mail sent";
        } catch (Exception e) {
            throw new RuntimeException(e); // Consider more specific exception handling
        }
    }

}

and this is the mail service (everything is configured and it works just fine , i just need to fetch the document from the already uploaded documents instead of the device