FileNotFoundException (Is a Directory)

This error occured to me because I was using file.mkdirs() with complete fileName .

Suppose your file path is emulated/0/test/images/img.jpg

Then remove last part from the path and use file.mkdirs() on result file

File file = new File("emulated/0/test/images/")

if (!file.exists()) {
    file.mkdirs();
}

Looks like in some cases filename is blank or null so File outputPath=new File(uploadDirPath + File.separator + fileName); will be a directory and here new FileOutputStream(outputPath); you try to write to a directory not to a file. So you should check if filename is not blank.

You have many errors in your code. For one, you only close the last InputStreams and OutputStreams; you should close each of them. The way you do things here, you have a resource leak.

Second, this is 2015; therefore drop File and use java.nio.file instead; plus, use try-with-resources.

Third: right now you upload in the project directory; don't do that when the application runs "live" on a server, this obviously won't work.

Sample:

private static final Path BASEDIR = Paths.get("/path/to/upload/directory");

// in the upload method:

Files.createDirectories(BASEDIR);

String fileName;
Path path;

for (final Part part: request.getParts()) {
    fileName = getFileName(part);

    if (fileName.isEmpty())
        continue;

    path = BASEDIR.resolve(fileName);

    try (
        final InputStream in = part.getInputStream();
    ) {
        Files.copy(in, path, StandardOpenOption.CREATE_NEW);
    }
}