newbie question: loading the jdbc driver & connecting to my db

I can't seem to make a connection to my postgresql database from
WebObject's EOModeler. I'd like to rule out the possibility that the
driver did not load properly. If I type

java -Djdbc.drivers=org.postgresql.Driver example.ImageViewer

and I get the following text, then that means that my driver loaded
properly, correct?

. . . This example tests the large object api of the example. . . .

If the driver loaded properly, and assuming that I started postmaster
with the -i option for tcp/ip connections, which I did, then as I see
it there are probably only two remaining reasons why I can't make a
connection: either the driver is not in the classpath (it is), or
I'm not typing in the url correctly. I've tried these three
variations (the text below is *exactly* what I type; my database is
called 'testdb'):

jdbc:postgresql:testdb
jdbc:postgresql://localhost/testdb
jdbc:postgresql://host:5432/testdb

My connection window gives me the option of specifying the name of my
driver. When I type in

postgresql.jar

then I get an error message saying that it couldn't find
postgresql.jar in the classpath and that I should check the
classpath. But in that same error window displayed in the classpath
list is the path to postgresql.jar

Any tips. Thanks in advance.

Russ

ps I'm running mac os 10.0.4 (Darwin), postgresql 7.1.2, and
WebObjects 5.0 (just the EOModeler so far)