Pooled connections in Tomcat

Hi,
I am trying to setup a DataSource for Postgre (7.2.2-1) in Tomcat
(4.1.12). Running on RedHat Linux 8, SDK is 1.4.1. I am using the
pg73jdbc2ee.jar jdbc-driver, which should have the support for
javax.sql.... See the Resource definition from server.xml below. I am
struggling with what value to use for the driverClassName. So far I have
tried
org.postgresql.Driver
org.postgresql.jdbc2.optional.PoolingDataSource
org.postgresql.jdbc2.optional.PooledConnectionImpl
org.postgresql.jdbc2.optional.ConnectionPool
All produce the same SQlException: Cannot load JDBC driver class 'null'

Can someone who has this running give me a hint please. I can connect to
Postgre by establishing a connection via the DriverManager, so
connection url, database config,.. are OK.

Thank you,
Thomas

<Resource
name="jdbc/pgdb"
auth="Container"
type="javax.sql.DataSource"/>

<ResourceParams name="jdbc/pgdb">
<parameter><name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value></parameter>
<parameter><name>username</name><value>user</value></parameter> <parameter><name>password</name><value>passwd</value></parameter>
<parameter><name>driverClassName</name>
<value>org.postgresql.jdbc2.optional.PoolingDataSource</value></parameter>
<parameter><name>url</name>
<value>jdbc:postgresql:db</value></parameter>
<parameter><name>maxActive</name><value>8</value></parameter>
<parameter><name>maxIdle</name><value>4</value></parameter>
</ResourceParams>