Simple Java SSH Client

An execution of a shell command via SSH can be done in Java, in just a few lines, using jcabi-ssh:

String hello = new Shell.Plain(
  new SSH(
    "ssh.example.com", 22,
    "yegor", "-----BEGIN RSA PRIVATE KEY-----..."
  )
).exec("echo 'Hello, world!'");

jcabi-ssh is a convenient wrapper of JSch, a well-known pure Java implementation of SSH2.

Here is a more complex scenario, where I upload a file via SSH and then read back its grepped content:

Shell shell = new SSH(
  "ssh.example.com", 22,
  "yegor", "-----BEGIN RSA PRIVATE KEY-----..."
);
File file = new File("/tmp/data.txt");
new Shell.Safe(shell).exec(
  "cat > d.txt && grep 'some text' d.txt",
  new FileInputStream(file),
  Logger.stream(Level.INFO, this),
  Logger.stream(Level.WARNING, this)
);

Class SSH, which implements interface Shell, has only one method, exec. This method accepts four arguments:

interface Shell {
  int exec(
    String cmd, InputStream stdin,
    OutputStream stdout, OutputStream stderr
  );
}

I think it’s obvious what these arguments are about.

There are also a few convenient decorators that make it easier to operate with simple commands.

Shell.Safe

Shell.Safe decorates an instance of Shell and throws an exception if the exec exit code is not equal to zero. This may be very useful when you want to make sure that your command executed successfully, but don’t want to duplicate if/throw in many places of your code.

Shell ssh = new Shell.Safe(
  new SSH(
    "ssh.example.com", 22,
    "yegor", "-----BEGIN RSA PRIVATE KEY-----..."
  )
);

Shell.Verbose

Shell.Verbose decorates an instance of Shell and copies stdout and stderr to the slf4j logging facility (using jcabi-log). Of course, you can combine decorators, for example:

Shell ssh = new Shell.Verbose(
  new Shell.Safe(
    new SSH(
      "ssh.example.com", 22,
      "yegor", "-----BEGIN RSA PRIVATE KEY-----..."
    )
  )
);

Shell.Plain

Shell.Plain is a wrapper of Shell that introduces a new exec method with only one argument, a command to execute. It also doesn’t return an exit code, but stdout instead. This should be very convenient when you want to execute a simple command and just get its output (I’m combining it with Shell.Safe for safety):

String login = new Shell.Plain(new Shell.Safe(ssh)).exec("whoami");

Download

You need a single dependency jcabi-ssh.jar in your Maven project (get its latest version in Maven Central):

<dependency>
  <groupId>com.jcabi</groupId>
  <artifactId>jcabi-ssh</artifactId>
</dependency>

The project is in GitHub. If you have any problems, just submit an issue. I’ll try to help.