Re: Newbie question - Applet works only in appletviewer

On 5 Jun 2002 at 16:29, Sam Varshavchik wrote:

Thank for your reply.

> Your browser's Java VM obviously does not have the PostgreSQL JDBC
> driver, jdbc*.jar, installed. Hence when the browser downloads your
> applet, and runs it, the PostgreSQL JDBC driver is not available.
>
> appletviewer reads your CLASSPATH, and pulls in the JDBC driver that
> way, but this mechanism is obviously not available in a real browser.
>
> There are several possible ways to fix this. One is to insert
> jdbc*.jar into your own applet's jar, so the browser ends up
> downloading both your applet, and the JDBC driver.

I tried this just to see if I could use quick-and-dirty for a temporary
solution, but couldn't get it to work. I tried all sorts of jar options
(including indexing), but no-go.

How is the VM supposed to know that the driver classes are within the
nested jar file? Am I missing something?

> Besides being a rather hefty download,
> this is not going to work anyway unless the PostgreSQL database is on
> the same server as your applet. The browser's security manager will
> prevent the application from logging in to any database not on the
> same server the applet was loaded from.

At present I'm not using a web-server, just viewing a local file. This
specific DB is maintained for outputting the system data, I think the
DB will stay on the same machine for the foreseeable future.

> A more common approach is to wrap all the database access code into a
> separate class that's left on the server, and invoked via RMI.

Being a complete Java newbie, I am now looking into RMI. Any pointers?

To use RMI what type of SERVER set-up do I need? At present I don't
even an web-server on the "server" side, as everything "runs" on the
same machine.

TIA for any further comments and help.

Shmuel Kahn
--
You're just jealous because the voices only talk to me.
Shmuel A. Kahn
Shmuel(at)Kam-motion(dot)com