SOLUTION: "SQL driver not found org.apache.derby.jdbc.ClientDriver" When Using Oracle with Sonar and Maven

I am new to Sonar and Maven, and have been perplexed for several hours with the "SQL driver not found org.apache.derby.jdbc.ClientDriver" error I was getting when running mvn sonar:sonar from the Windows command line after starting the Sonar server.

What is not clear in the instructions is that you must modify both <sonar path>\conf\sonar.properties and <maven path>\conf\settings.xml to get this to work. The Sonar properties tell the Sonar server what database driver to use in the Sonar server, and the Maven settings file tells Maven what database driver to use when it is running Sonar.

Here are the changes I made to connect to my local Oracle XE instance:

sonar.properties

...

sonar.jdbc.username: sonar
sonar.jdbc.password: sonar

...

# Comment the following lines to deactivate the default embedded database.
#sonar.jdbc.url: jdbc:derby://localhost:1527/sonar;create=true
#sonar.jdbc.driverClassName: org.apache.derby.jdbc.ClientDriver
#sonar.jdbc.validationQuery: values(1)

...

sonar.jdbc.url: jdbc:oracle:thin:@localhost:1521:xe
sonar.jdbc.driverClassName: oracle.jdbc.driver.OracleDriver
sonar.jdbc.validationQuery: select 1 from dual

settings.xml

<profiles>
  ...
  <profile>
    <id>sonar</id>
    <activation>
      <activeByDefault>true</activeByDefault>
    </activation>
    <properties>
      <sonar.jdbc.url>
      jdbc:oracle:thin:@localhost:1521:xe</sonar.jdbc.url>
      <sonar.jdbc.driver>
      oracle.jdbc.driver.OracleDriver</sonar.jdbc.driver>
      <sonar.jdbc.username>sonar</sonar.jdbc.username>
      <sonar.jdbc.password>sonar</sonar.jdbc.password>
      <sonar.host.url>http://localhost:9000</sonar.host.url>
    </properties>
  </profile>
</profiles>