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[eclipse-incubator-e4-dev] [resources] Java7 / JSR203 and EFS
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Hi
all,
I investigated a
little bit more about JSR203 (nio2 / filesystem access),
and here's some data
points:
- The most current
data about JSR203 is from the binary early
access download [1].
Install this on your system, read the
sources, try it out or generate
Javadocs from it -- the original
JSR203 document as from the JCP is
outdated, e.g. the package
name changed from java.nio.filesystem to java.nio.file.
The full Jdk7 EA
downloads also don't have nio2 in it yet!
- A 1-hour YouTube
video (from a techtalk at Google, May 1) is
available here
[2]
- A nice list of
additional pointers is here
[3], with a (slightly outdated)
HTML overview here
[4].
In terms of its
relation to EFS, I think the more interesting bits are
- Monitoring
API, which Szymon has mentioned already
- File
Attribute Views, which allow requesting a set of file
attributes
with optimized operations. EFS only has
IFileStore#fetchInfo(),
which is OK right now (since all info to be fetched
is available by
means of a stat() call), but is less than optimal if we
want to fetch
other kinds of attribute information... since we wouldn't
want to burden
clients which only need the modtime, for instance, with a
full fetchInfo()
that fetches information not needed.
- Creating
Symbolic Links
- Allowing
URI for converting from/to File/Path -- nice for EFS
:-)
- DirectoryStream for async directory retrieval -- all
other operations are
synchronous, so I'm questioning whether we really
need full async
support in EFS for reading attributes etc. I haven't yet
fully understood
the AsynchronousFilechannel class.
- Support for
Locking files against other programs
- Path.isSameFile(Path) basically a fast equals()
without getCanonicalPath()
I find this a very interesting feature for Alias
Management, depending on the
algorithms to be used... just imagine being
able to use a very fast UNIX
inode number for checking fiel equality,
instead of doing getCanonicalPath().
- Provider
Interface, so if we're writing an EFS implementation based on
JSR
203, adopters can implement a custom JSR203 filesystem
beneath.
EFS is better than
JSR203 when it comes to progress reporting and cancellation
--
all the JSR203 operations seem atomic (readAttributes(), copyTo(),
moveTo())
whereas
EFS allows IProgressMonitor for these operations.
Attached is a little
test program I wrote (under EPL), if you are interested.
Of course, this
needs the JSR203 ea from [1] to run :-)
The output of my
program is this:
Same!
p2URI: file:///C:/PROGRA~1/
realpath: C:\Program Files
canonical: C:\Program
Files
compareTo: 0
attrs:
{owner=BUILTIN\Administrators,
acl=[BUILTIN\Users:READ_ACL/EXECUTE/READ_NAMED_ATTRS/READ_ATTRIBUTES/SYNCHRONIZE/READ_DATA:ALLOW,
BUILTIN\Users:FILE_INHERIT/DIRECTORY_INHERIT/INHERIT_ONLY:ALLOW, ...]}
Cheers,
--
Martin Oberhuber, Senior Member of Technical
Staff, Wind River
Target Management Project
Lead, DSDP PMC Member
Attachment:
jsr203test.zip
Description: jsr203test.zip
