JNDI datasource update trouble: Cannot create JDBC driver of class '' for connect URL 'null'

Issue:

You are updating your context and web files as instructed here:  JNDI Services on Apache Tomcat

...You have also ensured that the JDBC driver used by your JNDI connection is placed in the lib directory of your application server (ex: apache-tomcat/lib).

...and you restart the server. Unfortunately, attempts to connect to your new JNDI resource result in the following error:

Cannot create JDBC driver of class '' for connect URL 'null'''

Resolution:

It is most likely that a previous JNDI configuration has been cached in your application server's work/cache directories. You must delete any cached configurations and restart the application server (the JNDI config for your JR server will be in a file named jasperserver-pro.xml, or <you-modified-context-name>.xml).

For example, in Tomcat, look for a file named "jasperserver-pro.xml" in the following directory, and ensure it is deleted so the new configuration takes effect:

• (tomcat root)apache-tomcat/conf/Catalina/localhost