Java Convert MultipartFile to File for large files

Question

I'm using the below method to convert MultipartFile to a File :

public File convert(MultipartFile file) throws IOException {
        File convFile = new File(file.getOriginalFilename());
        convFile.createNewFile();
        FileOutputStream fos = new FileOutputStream(convFile);
        fos.write(file.getBytes());
        fos.close();
        return convFile;
}

Wich work's fine but for large files I got this exception :

java.lang.OutOfMemoryError: Java heap space

I added more heap but still having the error.

So is there a programmatic way to fix this maybe splitting the multipart file to smaller chunks while converting, but I'm not sure how to code it.

Any help or suggestion would be greatly appreciated.

Solution

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;
  }

Comments

[Abdennacer Lachiheb]

it show this error cannot resolve method 'copy(java.io.InputStream, java.io.FileOutputStream) on this line Files.copy(...)

[Abdennacer Lachiheb]

This method doesn't save the file I got FileNotFoundException

[PowerStat]

Sorry then you have to add a create statement first.

[Abdennacer Lachiheb]

what do you mean by create statement ?

[Pavel Molchanov]

public File convert(MultipartFile file) throws IOException { File convFile = new File(file.getOriginalFilename()); convFile.createNewFile(); file.transferTo(convFile); return convFile; }

[PowerStat]

I checked the api and the createNewFile is not helpful. Looks like the point might be your environment - are you running with servlet 3.x api?

[jannis]

Stream will not be closed in case of an exception. try-with-resources should be used here (FileOutputStream fos = new FileOutputStream(convFile)).

[jannis]

I don't know where you took Files.copy(InputStream, OutputStream) from, but the input stream should probably be closed properly as well (but that depends on the library).

[jannis]

@AbdenaceurLichiheb it's a mistake probably and the OP meant either IOUtils#copy from Apache Commons IO or Guava's ByteStreams#copy.

[Firman Wijaya]

@AbdenaceurLichiheb Updated my answer. @jannis Files.copy(InputStream, OutputStream) is actually a private method of java.nio.file.Files class. My mistake

[Firman Wijaya]

@AbdenaceurLichiheb Files.readAllBytes() reads all bytes into memory and potentially causes OOME. You should try to read from stream instead.

[jannis]

You have an error in Files.copy(file.getInputStream(), convFile.toPath()). Should be Files.copy(is, convFile.toPath()). Otherwise you open two streams and leave one hanging.