Re: Newbie question - Applet works only in appletviewer - Mailing list pgsql-jdbc

Hi Shmuel,

The problem is that you are not running a webserver, in normal situations you need to download a HTML file which incorporates the applet, and also an archive tag which says where the jar resides where the applet is located and how the JAR is named. So when you use an applet and use the jdbc driver, you need to include your applet and the driver in a JAR file, create an HTML file which tels the navigator/explorer where to find the code, and then run it.

We have had the same problems, we wanted to quickly see how the applet looked like (for an embedded logging tool that dumped its data into a database directly) in a navigator/explorer, but this doesn't work, because the explorer only nows where to find the applet, but not the rest. The explorer/navigator has no knowledge of CLASSPATH settings whatsoever. So the only remedy is to run a webserver, and create the html file and the jar files,

Hope this helps,

Richard

Shmuel A. Kahn wrote:

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@Kam-motion.com


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