OutputStream stream = null;
try {
FileSystemStorage filesystem = FileSystemStorage.getInstance();
String path = filesystem.getAppHomePath() + filesystem.getFileSystemSeparator() + "file.csv";
stream = FileSystemStorage.getInstance().openOutputStream(path);
writeFile(stream);
Message message = new Message("See attached file");
message.setAttachmentMimeType("text/csv");
message.setAttachment(path);
Display.getInstance().sendMessage(null, "Your CSV file", message);
} catch (Exception e) {
throw new FileSaveException(e);
} finally {
Util.cleanup(stream);
}