Questions on the NIO.2 API

[Dr Andrew John Hughes]

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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