Accessing files and directories

To access and perform operations on an existing file or directory in the device file system:

1. Open a FileConnection to the file or directory by calling the Connector.open method with the complete URL of the file or directory. The URL is a string with the format file://<host>/<path> as defined in RFC 1738 and RFC 2396. The host is normally left empty and the path contains the full path to the file or directory.

   Note: The Connector.open method does not check whether the file or directory specified by the URL exists, so you can open a connection to a nonexistent file or directory.

   You can specify the URL in one of the following ways:

   • Use an FC API system property to retrieve the URL of a default storage directory and extend it with your own path, for example:

     String url = System.getProperty("fileconn.dir.music") + "MyMusic/song.mp3";

     It is recommended that you use this solution whenever possible, since it is likely to work on the widest range of devices.

   • Use a virtual root and directory and extend them with your own path, on Nokia Asha software platform devices, for example:

     String url = "file:///" + "Phone/" + "_my_music/" + "song.mp3";

   • Use the full logical directory and file path, on Series 40 devices, for example:

     String url = "file:///C:/predefgallery/predefmusic/song.mp3";

   Note: Do not mix logical and virtual roots and directories in the same URL. If you mix them, the Java Runtime throws an exception.

   The following code snippet opens a FileConnection to the file MyMusic/song.mp3 located in the default directory for storing music files.

   String url = System.getProperty("fileconn.dir.music") + "MyMusic/song.mp3";
   FileConnection fc;
   try {
       fc = (FileConnection)Connector.open(url);
       // use the fc object to perform operations on the file (see steps 2-4 of this example)
   } catch (IllegalArgumentException iae) {
   } catch (ConnectionNotFoundException cnfe) {
   } catch (IOException ioe) {
   } catch (SecurityException se) {
   } // catch any other exceptions

2. Check that the file or directory exists by calling the exists method on the FileConnection instance. If you try to perform an operation on a nonexistent file or directory, the Java Runtime throws an exception.

   if (!fc.exists()) {
       // If the file or directory does not exist,
       // program the MIDlet to behave accordingly
   }

3. Perform the required operations on the file or directory by using the methods provided by the FileConnection interface.

   If you write data to an output stream of the FileConnection instance (either an OutputStream or a DataOutputStream) and want the data to be immediately committed, but do not want to close the output stream itself, call the output stream's flush method.

   The following code snippet checks that the target file is writable, opens a DataOutputStream to the file, writes data to the DataOutputStream, and then immediately commits the changes by calling the DataOutputStream.flush method. When the DataOutputStream is no longer needed, it is closed. Closing the DataOutputStream also commits any remaining changes.

   if (!fc.canWrite()) {
       // If the file is not writable,
       // abort the writing process
   }
   
   // Open a DataOutputStream to the file
   DataOutputStream dos = fc.openDataOutputStream();
   
   // Write data to the DataOutputStream
   
   // Commit the data to file
   dos.flush();
   
   // Write more data to the DataOutputStream
   
   // Close the DataOutputStream and commit any data not yet flushed
   dos.close()

4. Close the FileConnection by calling its close method.

   fc.close();