[Jscheme-user] Re: Database Lessons for the Tutorial

[Timothy J. H. <tim...@ma...>]

On Mar 25, 2004, at 4:45 PM, Ken Anderson wrote:

> I think this would be great!  And Tim, i like the new interactive 
> Tutorial!
Thanks.... its starting to take shape nicely....
I'm having fun teaching CS concepts (abstraction, procedure calling) 
without
doing any numerical calculation at all, and still doing interesting 
examples....
I just presented this curriculum in the SIGCSE 2004 conference and the 
talk
went pretty well.

I'd like to provide a machine that anyone could use to try out the web 
programming
ideas, but I have to work on the security issues a little more first. 
For now,
the tutorial is available here:
       
http://tat.cs.brandeis.edu:8090/spr04/typcs04/tutorial/intro.servlet
This uses the latest version of the jscheme teaching webapp which 
includes
a U-method for uploading and editing servlets with a web interface, and 
the
V-method for getting color coded error checked versions of servlets and 
applets
using a web interface. I can give U-method access to interested 
jscheme-users
who want to play with it. Or you can download the webapp at
      http://tat.cs.brandeis.edu:8090/spr04/jscm.tgz
and install it in a servlet container like tomcat, jetty, or resin....

>
> I think we should exchange some code as you write the tutorial so we 
> can come up with an appropriate style.
Good idea. I'm including the code I use for databases below.

I usually create a connection when the webapp is first loaded and then 
use that connection
to define a procedure dbquery that sends strings to the database and 
gets a list of lists back.
The first row gives the types of the columns (metainfo).

The db.scm procedure below defines the following procedures
;(define database 'mysql)
(define database 'hsqldb)  ;; this specifies which of the databases is 
going to be used mysql or hsqldb
;; This defines the proper driver
(define jdbc-driver ....
(define jdbc-driver-class (java.lang.Class.forName jdbc-driver))
(define (connect host/db user pw)  ; this creates a connection to the 
specified DB
(define (handlequery con query)  ; this sends the query to the DB and 
returns a list of lists as above
(define (runquery host/db user pw query) ;; this combines connect and 
handlequery
(define (toMYSQL x) ;; this generates an SQL quoted string from a 
JScheme string
   (define (toHSQL x) ;; this generates an HSQL quoted string, with all 
(')s doubled (''),
(define toSQL ;; this selects the quoting mechanism based on which 
database is being used....