A
SFTPv3Client
represents a SFTP (protocol version 3)
client connection tunnelled over a SSH-2 connection. This is a very simple
(synchronous) implementation.
Basically, most methods in this class map directly to one of
the packet types described in draft-ietf-secsh-filexfer-02.txt.
Note: this is experimental code.
Error handling: the methods of this class throw IOExceptions. However, unless
there is catastrophic failure, exceptions of the type
SFTPv3Client
will
be thrown (a subclass of IOException). Therefore, you can implement more verbose
behavior by checking if a thrown exception if of this type. If yes, then you
can cast the exception and access detailed information about the failure.
Notes about file names, directory names and paths, copy-pasted
from the specs:
- SFTP v3 represents file names as strings. File names are
assumed to use the slash ('/') character as a directory separator.
- File names starting with a slash are "absolute", and are relative to
the root of the file system. Names starting with any other character
are relative to the user's default directory (home directory).
- Servers SHOULD interpret a path name component ".." as referring to
the parent directory, and "." as referring to the current directory.
If the server implementation limits access to certain parts of the
file system, it must be extra careful in parsing file names when
enforcing such restrictions. There have been numerous reported
security bugs where a ".." in a path name has allowed access outside
the intended area.
- An empty path name is valid, and it refers to the user's default
directory (usually the user's home directory).
If you are still not tired then please go on and read the comment for
setCharset(String)
.
canonicalPath
public String canonicalPath(String path)
throws IOException
Have the server canonicalize any given path name to an absolute path.
This is useful for converting path names containing ".." components or
relative pathnames without a leading slash into absolute paths.
path
- See the comment
for the class for more details.
close
public void close()
Close this SFTP session. NEVER forget to call this method to free up
resources - even if you got an exception from one of the other methods.
Sometimes these other methods may throw an exception, saying that the
underlying channel is closed (this can happen, e.g., if the other server
sent a close message.) However, as long as you have not called the
close()
method, you are likely wasting resources.
closeFile
public void closeFile(SFTPv3FileHandle handle)
throws IOException
Close a file.
handle
- a SFTPv3FileHandle handle
createFile
public SFTPv3FileHandle createFile(String fileName)
throws IOException
fileName
- See the comment
for the class for more details.
- a SFTPv3FileHandle handle
createFile
public SFTPv3FileHandle createFile(String fileName,
SFTPv3FileAttributes attr)
throws IOException
Create a file and open it for reading and writing.
You can specify the default attributes of the file (the server may or may
not respect your wishes).
fileName
- See the comment
for the class for more details.attr
- may be null
to use server defaults. Probably only
the uid
, gid
and permissions
(remember the server may apply a umask) entries of the SFTPv3FileHandle
structure make sense. You need only to set those fields where you want
to override the server's defaults.
- a SFTPv3FileHandle handle
createFileTruncate
public SFTPv3FileHandle createFileTruncate(String fileName)
throws IOException
fileName
- See the comment
for the class for more details.
- a SFTPv3FileHandle handle
createFileTruncate
public SFTPv3FileHandle createFileTruncate(String fileName,
SFTPv3FileAttributes attr)
throws IOException
reate a file (truncate it if it already exists) and open it for reading and writing.
You can specify the default attributes of the file (the server may or may
not respect your wishes).
fileName
- See the comment
for the class for more details.attr
- may be null
to use server defaults. Probably only
the uid
, gid
and permissions
(remember the server may apply a umask) entries of the SFTPv3FileHandle
structure make sense. You need only to set those fields where you want
to override the server's defaults.
- a SFTPv3FileHandle handle
createSymlink
public void createSymlink(String src,
String target)
throws IOException
Create a symbolic link on the server. Creates a link "src" that points
to "target".
src
- See the comment
for the class for more details.target
- See the comment
for the class for more details.
fsetstat
public void fsetstat(SFTPv3FileHandle handle,
SFTPv3FileAttributes attr)
throws IOException
Modify the attributes of a file. Used for operations such as changing
the ownership, permissions or access times, as well as for truncating a file.
handle
- a SFTPv3FileHandle handleattr
- A SFTPv3FileAttributes object. Specifies the modifications to be
made to the attributes of the file. Empty fields will be ignored.
fstat
public SFTPv3FileAttributes fstat(SFTPv3FileHandle handle)
throws IOException
Retrieve the file attributes of an open file.
handle
- a SFTPv3FileHandle handle.
- a SFTPv3FileAttributes object.
getCharset
public String getCharset()
The currently used charset for filename encoding/decoding.
- The name of the charset (
null
if the platform's default charset is being used)
getProtocolVersion
public int getProtocolVersion()
Returns the negotiated SFTP protocol version between the client and the server.
- SFTP protocol version, i.e., "3".
ls
public Vector ls(String dirName)
throws IOException
List the contents of a directory.
dirName
- See the comment
for the class for more details.
lstat
public SFTPv3FileAttributes lstat(String path)
throws IOException
Retrieve the file attributes of a file. This method
does NOT follow symbolic links on the server.
path
- See the comment
for the class for more details.
- a SFTPv3FileAttributes object.
mkdir
public void mkdir(String dirName,
int posixPermissions)
throws IOException
Create a new directory.
dirName
- See the comment
for the class for more details.posixPermissions
- the permissions for this directory, e.g., "0700" (remember that
this is octal noation). The server will likely apply a umask.
mv
public void mv(String oldPath,
String newPath)
throws IOException
Move a file or directory.
oldPath
- See the comment
for the class for more details.newPath
- See the comment
for the class for more details.
openFileRO
public SFTPv3FileHandle openFileRO(String fileName)
throws IOException
Open a file for reading.
fileName
- See the comment
for the class for more details.
- a SFTPv3FileHandle handle
openFileRW
public SFTPv3FileHandle openFileRW(String fileName)
throws IOException
Open a file for reading and writing.
fileName
- See the comment
for the class for more details.
- a SFTPv3FileHandle handle
read
public int read(SFTPv3FileHandle handle,
long fileOffset,
byte[] dst,
int dstoff,
int len)
throws IOException
Read bytes from a file. No more than 32768 bytes may be read at once.
Be aware that the semantics of read() are different than for Java streams.
- The server will read as many bytes as it can from the file (up to
len
),
and return them. - If EOF is encountered before reading any data,
-1
is returned.
- If an error occurs, an exception is thrown
- For normal disk files, it is guaranteed that the server will return the specified
number of bytes, or up to end of file. For, e.g., device files this may return
fewer bytes than requested.
handle
- a SFTPv3FileHandle handlefileOffset
- offset (in bytes) in the filedst
- the destination byte arraydstoff
- offset in the destination byte arraylen
- how many bytes to read, 0 < len <= 32768 bytes
- the number of bytes that could be read, may be less than requested if
the end of the file is reached, -1 is returned in case of
EOF
readLink
public String readLink(String path)
throws IOException
Read the target of a symbolic link.
path
- See the comment
for the class for more details.
rm
public void rm(String fileName)
throws IOException
Remove a file.
fileName
- See the comment
for the class for more details.
rmdir
public void rmdir(String dirName)
throws IOException
Remove an empty directory.
dirName
- See the comment
for the class for more details.
setCharset
public void setCharset(String charset)
throws IOException
Set the charset used to convert between Java Unicode Strings and byte encodings
used by the server for paths and file names. Unfortunately, the SFTP v3 draft
says NOTHING about such conversions (well, with the exception of error messages
which have to be in UTF-8). Newer drafts specify to use UTF-8 for file names
(if I remember correctly). However, a quick test using OpenSSH serving a EXT-3
filesystem has shown that UTF-8 seems to be a bad choice for SFTP v3 (tested with
filenames containing german umlauts). "windows-1252" seems to work better for Europe.
Luckily, "windows-1252" is the platform default in my case =).
If you don't set anything, then the platform default will be used (this is the default
behavior).
charset
- the name of the charset to be used or null
to use the platform's
default encoding.
setstat
public void setstat(String path,
SFTPv3FileAttributes attr)
throws IOException
Modify the attributes of a file. Used for operations such as changing
the ownership, permissions or access times, as well as for truncating a file.
path
- See the comment
for the class for more details.attr
- A SFTPv3FileAttributes object. Specifies the modifications to be
made to the attributes of the file. Empty fields will be ignored.
stat
public SFTPv3FileAttributes stat(String path)
throws IOException
Retrieve the file attributes of a file. This method
follows symbolic links on the server.
path
- See the comment
for the class for more details.
- a SFTPv3FileAttributes object.
write
public void write(SFTPv3FileHandle handle,
long fileOffset,
byte[] src,
int srcoff,
int len)
throws IOException
Write bytes to a file. If len
> 32768, then the write operation will
be split into multiple writes.
handle
- a SFTPv3FileHandle handle.fileOffset
- offset (in bytes) in the file.src
- the source byte array.srcoff
- offset in the source byte array.len
- how many bytes to write.