Re: java.lang.ClassNotFoundException loading JDBC driver - Mailing list pgsql-jdbc

On 10 Feb 2003, Dave Cramer wrote:

> Ernst,
>
> try running with java -d to show debugging information, it will show you
> the classpath it is using

That option isn't recognized by the JVM I'm using.


Anyway, my problem's been solved by another reader. Note to self:

Rule #1: Just because you've read the docs, doesn't mean you actually know
everything in there.

Rule #2: The following two are _not_ equivalent:

export CLASSPATH=.:foo.jar
java -jar bar.jar

export CLASSPATH=.:foo.jar:bar.jar
java MainClass

Where MainClass is the main class in bar.jar.


I'm not yet 100% confident on the semantics of class loading, but I know a
little more than I did yesterday, which is always a good thing :-)

Thanks.


Ernst Jan


>
> Dave
> On Sun, 2003-02-09 at 16:27, Ernst Jan Plugge wrote:
> > Hi,
> >
> >
> > Ik know this is a FAQ, but this looks different.
> >
> > While loading the pgsql jdbc driver (using Class.forName() as the
> > documentation suggests) I get a ClassNotFoundException:
> >
> > Exception in thread "main" java.lang.ClassNotFoundException:
> > org.postgresql.Driver
> >
> > even though the JAR file _is_ on my classpath. I've tried both the
> > CLASSPATH environment variable, and the -cp command line argument. The
> > test app I use is extremely bare bones, uses nothing beyond JDBC, and only
> > tries to load the driver and establish a connection.
> >
> > If I try to execute the class org.postgresql.Driver directly, with the
> > same classpath specification, the class is found, and I get (as expected)
> > an error message saying the class has no main method. This suggests that
> > my classpath is okay.
> >
> > If I move the JAR file into the JVM's lib/ext directory, things work
> > perfectly. I need to be able to use the driver without doing that,
> > however. What am I doing wrong?
> >
> > I'm using the pg73jdbc3.jar from jdbc.postgresql.org, downloaded today.
> > My JVM is j2sdk1.4.1_01 from Sun, on Red Hat Linux 8.0
> >
> > I also tried the 7.2, 7.1 and 7.0 drivers, and JVM jdk1.3.1_06 from Sun.
> > (I used pg73jdbc2.jar instead of pg73jdbc3.jar there)
> >
> > My test app is very simple:
> >
> > import java.sql.*;
> >
> > public class TestApp
> > {
> >   public static void main( String argv[] ) throws
> >     java.sql.SQLException, java.lang.ClassNotFoundException
> >   {
> >     Class.forName( "org.postgresql.Driver" );
> >     String url = "jdbc:postgresql://dbhost:5432/test";
> >     Connection conn = DriverManager.getConnection( url, "test", "xxxxxxxx" );
> >   }
> > }
> >
> >
> > Ernst Jan
> >
> >
> >
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