Commons VFS and Java.net.URL - Adding support for “sftp://” protocol

Question

We're trying to use Apache Commons VFS to access something over SFTP. It claims to support SFTP, however we're getting a MalformedURLException when it starts. Digging around I see that apache vfs is using java.net.URL. However the documentation tells me that it doesn't actually support sftp:// URLs.

Protocol handlers for the following protocols are guaranteed to exist on the search path :-

    http, https, ftp, file, and jar

Protocol handlers for additional protocols may also be available.

I'm using java 1.6.0 on Linux. How can I prevent java.net.URL from throwing a wobbly when it sees a sftp:// URL? I need to keep using the Apache commons VFS library, which uses java.net.URL.

Answer 1

See the list of dependencies that commons-vfs requires for sftp to work. Once JSch is in the classpath, your exception no longer happen. Have a look at Apache's Wiki for examples of connecting via sftp.

Answer 2

I've never used VFS before, but it looks like you'd need to (at least) register an SFTP FileProvider. It looks like it requires something like:

DefaultFileSystemManager fsm = ... /* Create and configure your FSM. */
fsm.addProvider("sftp", new SftpFileProvider());

There is probably a way to do the same thing through configuration file syntax.

Answer 3

Have a look at this description about how to implement a new URL protocol handler (the document describes an LDAP kind-of-URL, but you should be able to generalize from that to your sftp scheme).

From the document:

As you can see, the only difference between the two examples is that we have used an LDAP URL in the second case. However, for running the LDAP sample you first will have to register the LDAP protocol handler of IAIK-JCE to tell the java.net URL framework where to look for the LDAP supporting classes of IAIK-JCE:

System.getProperties().put("java.protocol.handler.pkgs", "iaik.x509.net");

After having registered the IAIK LDAP protocol handler, an IAIK-JCE LdapURLConnection object is returned when calling url.openConnection for an LDAP URL.

(emphasis mine)

Answer 4

I use jsch to handle sftp and ssh. It won't help you preventing an exception from java.net.URL, but it will help you doing sftp stuff.

Answer 5

Depending on how your code is structured, you could remove the s before you give the string to the URL parsing method, set a flag, and if it validates, check that flag and put it back if it's set. It's ugly, but it'll provide a workaround.