code: private void loadOverridesFromSystemProperties() {
          PropertyName[] names = PropertyName.values();
          for (PropertyName propertyName: names){
              String sysProp = System.getProperty(propertyName.name);
              if(sysProp != null){
                  properties.put(propertyName.name, sysProp);
              }
          }
      }
docs: A system property, if provided, will override a property from a file <code>activejdbc.properties</code>.
  That is only if defined in {@link PropertyName}.