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From "Alan Newberger" <a...@plumbdesign.com>
Subject RE: shell connector
Date Fri, 11 Jan 2002 16:27:30 GMT
I'm working on something very similar, I have a management servlet that uses rhino to wrap
important container objects as javascript objects.  You can then send javascript function
definitions and commands over HTTP.  Basically this is the plumbing for a nice ant task that
will deploy a webapp to a remote server.  After building a WAR, Ant will transfer the WAR
to a remote tomcat server, remove an existing context and clear it out of the filesystem if
necessary, and then (re)deploy the WAR.  This allows WAR deployment and redeployment to be
part of a build process without needing access to the filesystem and, most importantly, without
the need to restart Tomcat.  The javascript infrastructure allows us to perform this task
and others in the future in a consistent general way (and securely, through the use of authentication
etc.).  It makes it really really easy to define new adminstration tasks that can then be
scripted remotely as part of a buildprocess, or through a utility tool.

HOWEVER, I feel that the ability to make third party management-type servlets (i.e., ContainerServlets)
is a bit broken currently.  The ContainerServlet interface exists, however it only properly
loads tomcat classes (from 'org.apache.catalina') correctly to have access to the various
container object necessary for management (is this a design decision? if so, why publicize
such an interface?).  One could write their own ServletWrapper to load servlets in a context
however they like, but the 'wrapperClass' property of a Context doesn't correctly induce a
Context to use that Wrapper class instead of StandardWrapper.  So for a third party to add
a ContainerServlet to Tomcat, they must either change Tomcat source (undesirable, it would
be nicer to be able to drop such a webapp in any Tomcat install) or reimplement a bunch of
things (extend StandardContext and override 'createWrapper()', use that Context's className
in a Context tag in server.xml, have that Context return the custom Wrapper, have that Wrapper
use the catalina class loader for its servlets, etc.).  If anyone thinks this is wrong and
there is an easier way to do it, please let me know it would make my life easier :)

-alan

________________________________________________________________________
 
p l u m b d e s i g n
 
alan newberger 
chief architect
157 chambers st ny ny 10007
p.212.381.0541 | f.212.285.8999


-----Original Message-----
From: Creighton Kirkendall [mailto:ckirkendall@hobsons-us.com]
Sent: Friday, January 11, 2002 11:08 AM
To: 'Tomcat Developers List'
Subject: RE: shell connector






I was just wondering why you do not want to use http as the underlying
protocol.  I do not believe it would be that difficult to write a shell
application to utilize the management web app in tomcat.  In fact with a
little abstraction this could be rather simplistic.  I may be totally off
base here on what you are trying to do. I personally think this would be a
good project and may even be interested in helping with it.  I have some
ideas on how to make it configurable so that as the manager adds new
commands we do not have to change the code of the shell.

Creighton Kirkendall

-----Original Message-----
From: Armijn Hemel [mailto:armijn@nl.linux.org] 
Sent: Friday, January 11, 2002 9:05 AM
To: Tomcat Developers List
Subject: Re: shell connector

On Thu, Jan 10, 2002 at 11:08:00AM -0800, Craig R. McClanahan wrote:

> > I'm working on a webapp, for which I want to build (eventually) some
shell
> > access for administration purposes. I want administrators to be able to
> > log into the application and perform maintenance through a UNIX like
shell.
> > I was thinking about writing this in Jython, but I wonder how I can do
this
> > best. Does this involve writing a new connector and if so, is it the
best
> > thing to do (and do others need it as well)?
> >
> 
> What's wrong with just using telnet or ssh, and running command line apps
> that update the *data* that underlies your web application?  I don't see
> any reason that all data updates need to be made through Tomcat.

Well, I prefer updates to be mode through one program for consistency.
If anything changes, it's easier to maintain/update one application, than
two.

I'll give a small example of a use I see. To manage servlerts in my Tomcat
instance I don't want to use the web (I'm a console guy and lynx is not my
favourite webbrowser). I'd rather use a shell like tool to control the
server.
As in, use ls (or dir, whatever you prefer) to see all webapps and use small
commands like `stop <webapp>'.

So, even though I appreciate your answers and suggestions (I am a stubborn
guy by nature :) I want to write it. I don't think I want to use HTTP as
the underlying protocol (and no one said servlets should use HTTP).
I'll flesh out the idea a bit more, see what's on the market (maybe JMX).

Thanks so far :)

armijn

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