JSch: SCP a File in Java

If you want to upload a file to another computer, SCP is an excellent way to go. And if you want to do it from within a Java program, your best bet is to use the JSch library from JCraft. They've implemented the SSH protocol purely in Java, and it works splendidly. I've written a nice little class that encapsulates the action of sending a file.

Using the class is pretty simple. It goes like this:

 FileSender fs = new FileSender("172.16.40.128", "user", "user");  
 boolean ret = fs.sendFile("/home/sschulte/Desktop/AllPhysics.wmv", "AllPhysics.wmv");  

The constructor takes a host, a username, and a password. The sendFile() method takes a source filename and a destination filename. It returns true if the upload was successful, false if it failed.

I developed it in Netbeans, and in order to use JSch, the first step is to download the JAR and add it as a library in your project. (When I first tried it, I downloaded the ZIP instead, and added the source to my project; this works, but it's not necessary to compile this library along with your project unless you plan to edit it. I didn't.)

Most of the code in this class is taken from the ScpTo example included in the ZIP file. I recommend reading it. Something to pay close attention to, however, is the SSH known_hosts file. Their example file doesn't take this into account, so if you just run their code, you get an unknown host exception and it doesn't work. So be sure to include the following:

 String knownHostsFilename = "/home/sschulte/.ssh/known_hosts";  
 jsch.setKnownHosts(knownHostsFilename);  

(This is, of course, after you instantiate your JSch object.)

I like it, and it works. But it definitely needs a few things before I'm satisfied.

• Read the known_hosts filename from a config file, rather than compiling it into the code.
• Have a config file for the host/username/password information, possibly for multiple hosts at once.
• Throw exceptions for various types of failures, rather that simply returning false.