Example configuration:

 <configuration>
   <data-source name="default"
     class="org.apache.avalon.excalibur.datasource.JdbcDataSource">
     <!-- configuration for JdbcDataSource -->
     <pool-controller min="5" max="10" 
       connection-class="my.overrided.ConnectionClass">
     <keep-alive>select 1</keep-alive>
     </pool-controller>
     <driver>com.database.jdbc.JdbcDriver</driver>
     <dburl>jdbc:driver://host/mydb</dburl>
     <user>username</user>
     <password>password</password>
   </data-source>
 </configuration>