Java Reference
In-Depth Information
// Read all basic attributes through the view
BasicFileAttributes bfa = bfv.readAttributes();
// Print some basic attributes
System.out.format("Size:%s bytes %n", bfa.size());
System.out.format("Creation Time:%s %n",
bfa.creationTime());
System.out.format("Last Access Time:%s %n",
bfa.lastAccessTime());
// Update the create time to the current time
FileTime newLastModifiedTime = null;
FileTime newLastAccessTime = null;
FileTime newCreateTime = FileTime.from(Instant.now());
// A null for time means youdo not want to update that time
bfv.setTimes(newLastModifiedTime,
newLastAccessTime,
newCreateTime);
}
catch (IOException e) {
e.printStackTrace();
}
}
}
Managing the Owner of a File
There are three ways to manage the owner of a file:
Files.getOwner()
and
Files.setOwner()
methods.
•
Using
Files.getAttribute()
and
Files.setAttribute()
methods using
"owner"
as the
attribute name.
•
Using
FileOwnerAttributeView
.
You need to work with
UserPrincipal
and
GroupPrincipal
interfaces to manage the owner of a file.
The owner of a file could be a user or a group. A
UserPrincipal
represents a user whereas a
GroupPrincipal
represents a group. When you read the owner of a file, you get an instance of
UserPrincipal
. Use the
getName()
method on the
UserPrincipal
object to get the name of the user. When you want to set the owner of a file, you
need to get an object of the
UserPrincipal
from a user name in a string form. To get a
UserPrincipal
from the
file system, you need to use an instance of the
UserPrincipalLookupService
class, which you can get using
the
getUserPrincipalLookupService()
method of the
FileSystem
class. The following snippet of code gets a
UserPrincipal
object for a user whose user id is
ksharan
:
•
Using the
FileSystem fs = FileSystems.getDefault();
UserPrincipalLookupService upls = fs.getUserPrincipalLookupService();
// Throws a UserPrincipalNotFoundException exception if the user ksharan does not exist
UserPrincipal user = upls.lookupPrincipalByName("ksharan");
System.out.format("User principal name is %s%n", user.getName());
