SCOUG-Programming Mailing List Archives

Date:	Wed, 19 Aug 1998 12:41:18 PDT
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: FTP Server Project

Content Type: text/plain

From Peter Skye:

I got a private email from Terry Warren which answered one of my posted
questions, and it's worth passing along to everyone.

I had asked how we'd be starting the ftp server once it's finished:

> > > > > 1. How, exactly, do you start this thing once it's written?

And Rollin had responded:

> > > > Probably something like:
> > > >
> > > > java FtpServer 21
> > > >
> > > > Where 21 is the port to listen to.

So I asked:

> > > Why are we putting the port on the command line? Why not in a setup
> > > file where it will join other things such as the user profile
> > > filename?

Terry, the most knowledgeable Java programmer I know, answered me
privately with the following:

> > ... one standard way
> > of dealing with these types of values is to use the system properties
> > object. It is similar to passing by command line (and in fact you can
> > pass them this way also) but is a little more flexible and can be
> > (more easily) adapted to persistent properties.
> >
> > The way it works is:
> >
> > (1) if you pass any command line switch defined with -D the jvm adds it
> > to the system properties array for your application.
> >
> > (2) the application can then access it using the System.getProperty()
> > method.
> >
> > (3) the properties can also be set by another program running in the
> > same jvm.
> >
> > so, in your example, you might pass the property as something like:
> >
> > java -Dscoug.ftpport=21 ftpserver
> > (you MUST put the switch before the program name)
> >
> > and in the program you would have code like:
> >
> > String ftpport = System.getProperty("scoug.ftpport", "21");
> > // the second parm is the default to be used if the property
> > is not defined
> >
> > or:
> >
> > int ftpport = Integer.parseInt(System.getProperty("scoug.ftpport",
> > "21"));
> >
> > Ideally, this code would be part of a startup class that could also
> > reference an existing serialized Property object containing other
> > configuration data; this is a better approach for persistent
> > properties.
> >
> > (I can supply a class of this type if needed).

Terry, thank you very much. I didn't know this capability was
available.

I now need to study the system properties object and system properties
array.

- Peter Skye

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