The API contains one class, two interfaces, and two exceptions. The
most important one of these is the FileConnection interface,
which extends the Connection interface and gives access
to directories and individual files.
Implementations of FileConnection are created using
the Connector.open() method. The argument of the open() method
is a URL with the format file://<host>/<path>,
as defined in RFC 1738 and RFC 2396 (RFC is the Request for Comments repository maintained
by the IETF Secretariat), where host is normally left
empty and path starts with the root of the file system
down to a particular file or directory. An example of a typical file URL in
a S60 device looks as follows:
file:///C:/data/Images/Image(001).jpg
The roots of the file system are device-specific and they don't necessarily
correspond to physical memory units since they are logically defined by the
device's operating system. Furthermore, some Nokia devices support virtual
roots and virtual directories, which act as links pointing to certain denoted
directories. For example, c:/ and e:/ are
physical roots. The corresponding virtual roots are Internal/ and Memory
card/. Virtual directories map to the same directories that are
defined in FC API System properties . This makes it easier to find locations
and also eases the security permissions, given that a MIDlet may have access
rights to the Internal/Images root but not necessarily
to the c:/ root. For more information on virtual file
systems, see FC
API Implementation notes.
The FileSystemRegistry class provides the listRoots() utility
method that returns an enumeration of the roots on the file system. This includes
both logical and virtual roots. The API also takes into account that certain
devices have the ability to have file systems added or removed at run time.
The FileSystemRegistry class provides methods for registering FileSystemListener listeners
that are called when the roots on the device are modified. It is recommended
for every application to register a FileSystemListener listener
to be informed about these changes and act accordingly.
Since the FC API is an optional extension, a system property has been
added to indicate the API's presence. The microedition.io.file.FileConnection.version system
property contains the implemented version of the API. Currently this property
should have the value 1.0 to indicate the current status
of the API or null if the API is not present. Another useful system property
is file.separator, which contains the character used
to separate directories, typically with the value "/".