Java Spring: Best Way to Convert a File to a Multipartfile

Java spring: best way to convert a File to a MultipartFile

InputStream stream =  new FileInputStream(file)
multipartFileToSend = new MockMultipartFile("file", file.getName(), MediaType.TEXT_HTML_VALUE, stream);

try this

How to convert a multipart file to File?

You can get the content of a MultipartFile by using the getBytes method and you can write to the file using Files.newOutputStream():

public void write(MultipartFile file, Path dir) {
    Path filepath = Paths.get(dir.toString(), file.getOriginalFilename());

    try (OutputStream os = Files.newOutputStream(filepath)) {
        os.write(file.getBytes());
    }
}

You can also use the transferTo method:

public void multipartFileToFile(
    MultipartFile multipart, 
    Path dir
) throws IOException {
    Path filepath = Paths.get(dir.toString(), multipart.getOriginalFilename());
    multipart.transferTo(filepath);
}

How to convert Image to multipart file in spring

I would suggest convert the image by using this code

FileInputStream input = new FileInputStream(fileItem);
MultipartFile multipartFile = new MockMultipartFile("fileItem",
            fileItem.getName(), "image/png", IOUtils.toByteArray(input));

If you would like to use CommonsMultipartFile, I think you should have into your pom file the commons-fileupload

<dependency>
   <groupId>commons-fileupload</groupId>
   <artifactId>commons-fileupload</artifactId>
   <version>1.3</version> 
</dependency>

The documentation of CommonsMultipartFile states that

NOTE: As of Spring 2.0, this class requires Commons FileUpload 1.1 or
higher. The implementation does not use any deprecated FileUpload 1.0
API anymore, to be compatible with future Commons FileUpload releases.
http://docs.spring.io/spring-framework/docs/2.0.8/api/org/springframework/web/multipart/commons/CommonsMultipartFile.html

Let me know if this worked for you

MultipartFile issue, unable to convert to File

getBytes() tries to load the whole byte array into memory which is causing your OOM what you need to do is stream the file and write it out.

Try the following:

private static Path convert(MultipartFile file) throws IOException {
  Path newFile = Paths.get(file.getOriginalFilename());
  try(InputStream is = file.getInputStream();
     OutputStream os = Files.newOutputStream(newFile))) {
     byte[] buffer = new byte[4096];
     int read = 0;
     while((read = is.read(buffer)) > 0) {
       os.write(buffer,0,read);
     }
  }
  return newFile;  
}

I changed your method to return a Path instead of File which is part of the java.nio package. The package is preferred over java.io as its been optimized more.

If you do need a File object you can call newFile.toFile()

Since it returns a Path object you can use the java.nio.file.Files class to relocate the file to your preferred directory once it has been written out

private static void relocateFile(Path original, Path newLoc) throws IOException {
  if(Files.isDirectory(newLoc)) {
    newLoc = newLoc.resolve(original.getFileName());
  }
  Files.move(original, newLoc);
}

Java Convert MultipartFile to File for large files

Does MultipartFile belong to Spring's package org.springframework.web.multipart? If so, you could do

  public File convert(MultipartFile file) throws IOException {
    File convFile = new File(file.getOriginalFilename());
    convFile.createNewFile();
      try(InputStream is = file.getInputStream()) {
        Files.copy(is, convFile.toPath()); 
      }
    return convFile;
  }

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