Questions on the NIO.2 API

[Martijn Verburg]

Hi all,

On Mon, Jan 31, 2011 at 4:05 PM, Dr Andrew John Hughes <
gnu_andrew at member.fsf.org> wrote:

> On 31 January 2011 15:57, Rémi Forax <forax at univ-mlv.fr> wrote:
> >  Le 31/01/2011 16:30, Martijn Verburg a écrit :
> >>
> >> Hi all,
> >>
> >> I've finally come back to this Chapter and am thinking about the various
> >> rough code samples I've written (running b127 on Windows XP SP3 32bit).
>  My
> >> next code sample simply takes the reader through some of the file system
> api
> >> in order to explore some of the basics.
> >>
> >> import java.io.IOException;
> >> import java.nio.file.*;
> >>
> >> public class Listing_2_1
> >> {
> >>    public static void main(String[] args) throws IOException
> >>    {
> >>        try (FileSystem fileSystem = FileSystems.getDefault())
> >>        {
> >>            Path timeSheetFile =
> >> fileSystem.getPath("C:/projects/timesheet.txt");
> >>            Path backupDir = fileSystem.getPath("H:/projects/");
> >>            Path backupFile =
> >> fileSystem.getPath("H:/projects/timesheet.txt");
> >>
> >>            timeSheetFile.checkAccess(AccessMode.READ);
> >>            backupDir.checkAccess(AccessMode.WRITE);
> >>
> >>            FileStore backupFileStore = backupDir.getFileStore();
> >>            if (!backupFileStore.type().equals("NTFS"))
> >>            {
> >>                throw new IOException("Suspicious storage type");
> >>            }
> >>
> >>            CopyOption copyOptions = StandardCopyOption.REPLACE_EXISTING;
> >>            timeSheetFile.copyTo(backupFile, copyOptions);
> >>        }
> >>    }
> >> }
> >>
> >> The code example is a pretty patsy one, but one gotcha in particular was
> >> noticed by earlier reviewers.
> >>
> >> The FileStore object's type is simply a String as opposed to a constant,
> >> enum or other defined type.  This makes it very hard to rely on for
> decision
> >> making (as per the if statement I have above).  I assume this is a
> >> limitation of being able to consistently detect the underlying storage
> type?
> >
> > Yes, the problem is that the string can be easily misspelled.
> > I wondering if it worth an API like this:
> >
> > interface FileStoreType {
> >  public String getName();
> > }
> >
> > public enum StandardFileStoreType implements FileStoreType {
> >  EXT3, EXT4, FAT32, NTFS;
> >  ...
> > }
> >
> > public class FileStoreTypes {
> >  public static FileStoreType getFileStoreType(final String name) {
> >     // StandardFileStoreType.valueOf(name)
> >     // otherwise new FileStoreType() {
> >     //   public String getName() {
> >     //      return name;
> >     //   }
> >     //};
> >  }
> > }
> >
> > In that case, the code can be rewrite to:
> > backupFileStore.type().equals(StandardFileStoreType.NTFS)) { ... }
> >
> >>
> >> Thanks again all.
> >> Martijn
> >> (@java7developer - twitter)
> >>
> >
> > Rémi
> >
> >
> >
>
> What happens if the file store uses a type not defined in the enum?
> It may be possible to misspell a String, but it's worse if the API is
> outdated before it even gets released because it only lists certain
> filesystems.
> --
> Andrew :-)

Free Java Software Engineer
> Red Hat, Inc. (http://www.redhat.com)
>
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>

Perhaps a compromise?  Have a certain defined set of StandardFileStoreTypes,
yet still allow more to be added on the fly? Perhaps something a little like
how CopyOptions are dealt with?  OK, I'm probably starting to get out of my
depth here :)

Cheers,
Martijn
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