Convert Object to multipart document (multipartFile) - Download and upload files

THE VISTA

I use the html part with a simple form like this:

<form th:action="@{/form}" method="post" enctype="multipart/form-data">
     <input type="file" name="file" class="form-control">
</form>

CONTROLLER

And in the controller you receive it this way:

@PostMapping("/form")
    public String guardar(Map<String, Object> model,
            @RequestParam("file") MultipartFile foto, RedirectAttributes flash, SessionStatus status) {

       // ... AQUI TUS OPERACIONES DE GRABADO, MODIFICADO, ETC.. 
        return "redirect:/listar";
    }

SERVICE

The interface for that of the changes that are required later:

public interface IUploadFileService {

    public Resource load(String filename) throws MalformedURLException;

    public String copy(MultipartFile file) throws IOException;
    public boolean delete(String filename);

    public void deleteAll();
    public void init() throws IOException;

}

This is the service I have prepared for uploading files.

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.UUID;

import org.slf4j.LoggerFactory;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.stereotype.Service;
import org.springframework.util.FileSystemUtils;
import org.springframework.web.multipart.MultipartFile;

@Service
public class UploadFileServiceImpl implements IUploadFileService {

    private final static String UPLOADS_FOLDER = "upload";

    private final org.slf4j.Logger log = LoggerFactory.getLogger(getClass());

    @Override
    public Resource load(String filename) throws MalformedURLException {
        Path pathFoto = getPath(filename);
        log.info("pathFoto: " + pathFoto);
        Resource recurso = null;

        recurso = new UrlResource(pathFoto.toUri());
        if (!recurso.exists() || !recurso.isReadable()) {
            throw new RuntimeException("No se puede cargar la imagen: " + pathFoto.toString());
        }

        return recurso;
    }

    @Override
    public String copy(MultipartFile file) throws IOException {

        String uniqueFilename = UUID.randomUUID().toString() + "_" + file.getOriginalFilename();

        Path rootPath = Paths.get(UPLOADS_FOLDER).resolve(uniqueFilename);

        log.info("rootPath:" + rootPath);

        Files.copy(file.getInputStream(), rootPath);

        return uniqueFilename;
    }

    @Override
    public boolean delete(String filename) {
        Path rootPath = getPath(filename);
        File archivo = rootPath.toFile();

        if (archivo.exists() && archivo.canRead()) {
            if (archivo.delete()) {
                return true;
            }
        }
        return false;
    }

    public Path getPath(String filename) {

        return Paths.get(UPLOADS_FOLDER).resolve(filename).toAbsolutePath();
    }

    @Override
    public void deleteAll() {
        FileSystemUtils.deleteRecursively(Paths.get(UPLOADS_FOLDER).toFile());

    }

    @Override
    public void init() throws IOException {
        Files.createDirectories(Paths.get(UPLOADS_FOLDER));

    }

}

DEVELOPMENT CONFIGURATION.

This configuration is so that while you are doing tests the files are deleted every time you restart the server. CARE FOR PRODUCTION ENVIRONMENTS

@SpringBootApplication
public class SpringBootDataJpaApplication implements CommandLineRunner {

    @Autowired
    IUploadFileService uploadFileService;

    public static void main(String[] args) {
        SpringApplication.run(SpringBootDataJpaApplication.class, args);
    }

    @Override
    public void run(String... args)throws Exception{
        uploadFileService.deleteAll();
        uploadFileService.init();
    }
}

SOME CLARIFICATIONS

It's actually very simple with the service. You only have to call the service in your controller with @Autowired for the injection of dependencies (xP) and execute your validations.

The operations are obvious:

• load(String filename) allows you to get the file from the server when it is already loaded.
• copy (MultipartFile file) copies the MultipartFile that you got from the form to the server in the folder defined in UPLOADS_FOLDER .
• delete(String filename) removes the file from the server if it exists.

In my case I am working with photos, hence many of the names refer to photos but it is useful for any file. The type validation part is already up to you.

FINAL RECOMMENDATIONS

I recommend you do all the tests first in an html form. This way you will not have to be thinking about JS and the backend. The change afterwards is easy.

  

I trust you are using spring-boot with annotations and not xml.