I'm trying to set up nemesis-forum in apache-tomcat-5.5.20 to use PostgreSQL and I keep getting this error:

ERROR jdbc.DataSourceConnectionProvider  - Could not retrieve Connection from DataSource
org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null'

I did some research and found this document: http://paperstack.com/tips/tomcat_config.html

I changed the datasource configuration from this:

<ResourceParams name="jdbc/MyDataSource">
    <parameter>
        <name>username</name>
        <value>"jspUser"</value>
    </parameter>
    <parameter>
        <name>password</name>
        <value>"jspUserPass"</value>
    </parameter>
    <parameter>
        <name>driverClassName</name>
        <value>"org.postgresql.Driver"</value>
    </parameter>
    <parameter>
        <name>url</name>
        <value>"jdbc:postgresql://localhost:5432/yazd"</value>
    </parameter>
    <parameter>
      <name>maxActive</name>
      <value>8</value>
    </parameter>
    <parameter>
      <name>maxIdle</name>
      <value>4</value>
    </parameter>
</ResourceParams>

to this:

<Resource
    name="jdbc/MyDataSource" auth="Container"
    type="javax.sql.DataSource"
    driverClassName="org.postgresql.Driver"
    url="jdbc:postgresql://localhost:5432/yazd"
    username="jspUser"
    password="jspUserPass"
    maxActive="8"
    maxIdle="4"
/>

as that article suggests, but it didn't make any difference.