Basic questions about VFS

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Basic questions about VFS

Jon Blower
Hi all,

I've just come across the Commons VFS project and I think it could be very
useful to me.  I have developed a Java implementation of the Styx protocol
for distributed systems (http://jstyx.sf.net).  In Styx, every resource is
represented as a set of virtual files, and so it should be straightforward
to represent these files using VFS.

I have a few questions about VFS.  I have looked on the Web for answers,
but apologies if I have missed something.

1) What is the status of the VFS project?  Is it still actively being
developed?  Is it planned to be a key part of any important Apache
projects?  (I am trying to establish whether the project has potential
longevity.)

2) When is a formal release planned?  At the moment is the only way to get
the software via the nightly builds?  The SVN repository
(http://svn.apache.org/viewcvs.cgi/) seems to say that the Commons project
is closing - is this true, or has the SVN repository moved somewhere else?

3) Are there any GUI apps (e.g. file system browsers) that interact with
VFS resources?

4) How does VFS deal with file permissions?  I have seen the isReadable()
etc methods but how can a new file be created with given permissions?
(Styx systems, like POSIX ones, have rwxrwxrwx file permissions).

5) Is asynchronous I/O supported?  I.e. can I send a message to write data
to a file and provide a callback for when the data are written?

Very sorry if I have posted to the wrong list (I wasn't sure if some of
these questions are for developers) and also sorry if this information is
on the Web.  Please tell me to RTFM (or point me to a web page!) if I have
missed something.

Regards, Jon

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Re: Basic questions about VFS

Mario Ivankovits
Hi!
>1) What is the status of the VFS project?
We are close before a 1.0 release.
>Is it still actively being developed?
Currently I am the only active committer, but there is a active user
base and some contributors.
>Is it planned to be a key part of any important Apache projects?
Not that I am aware of. From our internal logs (those which other
projects fail if I made a mistake) I can see its used in
cocoon, excalibur, forrest and log4j-chainsaw (log viewer), though I
know of some other people who use vfs
as part of their productive system.
>2) When is a formal release planned?
see above
>At the moment is the only way to get the software via the nightly builds?
Yes - and svn head.
>The SVN repository (http://svn.apache.org/viewcvs.cgi/) seems to say that the Commons project
>is closing - is this true, or has the SVN repository moved somewhere else?
>  
You must dive into jakarta/commons not the top level commons.
>3) Are there any GUI apps (e.g. file system browsers) that interact with
>VFS resources?
>  
log4j-chainsaw
>4) How does VFS deal with file permissions?
VFS do not deal with file permissions, its up to the used library and in
fact at last by the operating system if a system is read-/writeable.
VFS do not have a api to change/set file permissions.
>5) Is asynchronous I/O supported?  I.e. can I send a message to write data
>to a file and provide a callback for when the data are written?
>  
Currently not, but might be a great addition.

Do not hesitate to ask further questions.

---
Mario


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Re: Basic questions about VFS

Jon Blower
Hi Mario,

Thanks very much for all this information.  The lack of file permissions
support could be a problem for me.  I understand why it's not there, as
many systems don't use permissions, but I was wondering if there could at
least be a system for setting and getting file permissions (if the correct
Capability is set) and for creating files and folders with given
permissions?

Perhaps there could be a "hasPosixPermissions" Capability, and if a file
has that capability, its permissions can be set and read?

As for the asynchronous I/O, that would be very useful too.  I might be
able to contribute something when I've understood VFS a bit better.

Regards, Jon

--------------------------------------------------------------
Dr Jon Blower              Tel: +44 118 378 5213 (direct line)
Technical Director         Tel: +44 118 378 8741 (ESSC)
Reading e-Science Centre   Fax: +44 118 378 6413
ESSC                       Email: [hidden email]
University of Reading
3 Earley Gate
Reading RG6 6AL, UK
--------------------------------------------------------------


On Tue, 6 Sep 2005, Mario Ivankovits wrote:

> Hi!
> >1) What is the status of the VFS project?
> We are close before a 1.0 release.
> >Is it still actively being developed?
> Currently I am the only active committer, but there is a active user
> base and some contributors.
> >Is it planned to be a key part of any important Apache projects?
> Not that I am aware of. From our internal logs (those which other
> projects fail if I made a mistake) I can see its used in
> cocoon, excalibur, forrest and log4j-chainsaw (log viewer), though I
> know of some other people who use vfs
> as part of their productive system.
> >2) When is a formal release planned?
> see above
> >At the moment is the only way to get the software via the nightly builds?
> Yes - and svn head.
> >The SVN repository (http://svn.apache.org/viewcvs.cgi/) seems to say that the Commons project
> >is closing - is this true, or has the SVN repository moved somewhere else?
> >
> You must dive into jakarta/commons not the top level commons.
> >3) Are there any GUI apps (e.g. file system browsers) that interact with
> >VFS resources?
> >
> log4j-chainsaw
> >4) How does VFS deal with file permissions?
> VFS do not deal with file permissions, its up to the used library and in
> fact at last by the operating system if a system is read-/writeable.
> VFS do not have a api to change/set file permissions.
> >5) Is asynchronous I/O supported?  I.e. can I send a message to write data
> >to a file and provide a callback for when the data are written?
> >
> Currently not, but might be a great addition.
>
> Do not hesitate to ask further questions.
>
> ---
> Mario
>
>
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> To unsubscribe, e-mail: [hidden email]
> For additional commands, e-mail: [hidden email]
>
>

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Re: Basic questions about VFS

Mario Ivankovits
Hi!
>Perhaps there could be a "hasPosixPermissions" Capability, and if a file
>has that capability, its permissions can be set and read?
>  
The main problem is the lack of support in the underlaying libraries.
Even for local files we might need a native library (I hate native
libraries) to set permissions as there is no real support in java.io.file.

And we have to figure out how to abstract the various different
permission systems.
For windows/unix this document might help:
http://docs.hp.com/en/B8725-90053/ch03s02.html

Maybe this might happen, though I cant promise it.

Ciao,
Mario


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Re: Basic questions about VFS

Jon Blower
Hi Mario,

Yes, I see the problem and I agree that native libraries would not be a
good solution.  However, there must be some underlying libraries (e.g. the
FTP libraries?) that understand file permissions.  Even if it weren't
available in VFS files that are underlain by java.io.File, perhaps it
would still be useful to have support in VFS for filesystems that do
support permissions in pure Java?  VFS could detect whether permissions
were supported and allow manipulation accordingly.

Cheers, Jon


--------------------------------------------------------------
Dr Jon Blower              Tel: +44 118 378 5213 (direct line)
Technical Director         Tel: +44 118 378 8741 (ESSC)
Reading e-Science Centre   Fax: +44 118 378 6413
ESSC                       Email: [hidden email]
University of Reading
3 Earley Gate
Reading RG6 6AL, UK
--------------------------------------------------------------


On Wed, 7 Sep 2005, Mario Ivankovits wrote:

> Hi!
> >Perhaps there could be a "hasPosixPermissions" Capability, and if a file
> >has that capability, its permissions can be set and read?
> >
> The main problem is the lack of support in the underlaying libraries.
> Even for local files we might need a native library (I hate native
> libraries) to set permissions as there is no real support in java.io.file.
>
> And we have to figure out how to abstract the various different
> permission systems.
> For windows/unix this document might help:
> http://docs.hp.com/en/B8725-90053/ch03s02.html
>
> Maybe this might happen, though I cant promise it.
>
> Ciao,
> Mario
>
>
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> To unsubscribe, e-mail: [hidden email]
> For additional commands, e-mail: [hidden email]
>
>

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Re: Basic questions about VFS

Stephen Colebourne
In reply to this post by Mario Ivankovits
--- Mario Ivankovits <[hidden email]> wrote:
> The main problem is the lack of support in the
> underlaying libraries.
> Even for local files we might need a native library
> (I hate native
> libraries) to set permissions as there is no real
> support in java.io.file.

See [io] FileSystemUtils for an example of using the
command line from Java to get the free space on the
drive. You could extend this [io] class to add file
permissions.

Stephen

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Re: Basic questions about VFS

Mario Ivankovits
In reply to this post by Jon Blower
Jon Blower wrote:
>However, there must be some underlying libraries (e.g. the
>FTP libraries?) that understand file permissions.
FTP do not support permission, the protocol itself didnt support it.

I am not sure, but I think the only library with "ACL" support is
webdav/slide.


Regards,
Mario


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