How does the resource of the connection get managed?

[PhilAndrew]

Can you explain how the resource of the connection is managed?

Lets say I have a class with a method doWork and this method does SSH commands frequently and gets called frequently, I think I should make a member of this class as a lazy val as:

lazy val ssh = SSH(?, ?, ?)

I am expecting that when I go to use ssh the first time, it will open the connection, then since the object is around as a member of this class, it will keep using the same connection.

Is this how it works?

What if I kept re-creating the SSH(...), would it cache the connection?

[dacr]

If you use the factories (object apply methods), it will be up to you to close the resource using close method, like that:

val ssh= SSH(host="localhost", username="test")
try {
  ssh.execute("ls")
} finally {ssh.close()}

But SSH object brings helper methods that auto-close resource for you :

val result = SSH.once(host="localhost", username="test") { ssh =>
  ssh.execute("ls")
}

Another one, with a persited shell session

val result = SSH.shell(host="localhost", username="test") {sh =>
   s"""My name is ${sh.execute("hostname")} and my uptime is ${sh.execute("uptime")}"""
}

In that last case, both commands hostname and uptime are executed within the same shell, the proof :

val result = SSH.shell(host="localhost", username="test") {sh =>
  sh.execute("HELLO=`hostname`")
  sh.execute("echo hello $HELLO")
}

You can also define such function in order to use your own safe autoclose mechanism :

def using[R, T<%{def close()}](getres: =>T)(proc : T => R):R = {
   val res=getres
   try {proc(res)} finally {res.close}
}

val result = using(SSH(host="localhost", username="test")) { ssh =>
  ssh.execute("ls")
}