code: public String getPropertyValue(final String propertyName, final String defaultPropertyValue) {
      return defaultIfUnset(getPropertyValue(propertyName, NOT_REQUIRED), defaultPropertyValue);
    }
docs: Gets the value of the configuration property identified by name.  The defaultPropertyValue parameter effectively
  overrides the required attribute indicating that the property is not required to be declared or defined.
  
  @param propertyName a String value indicating the name of the configuration property.
  @param defaultPropertyValue the default value for the configuration property when the property is undeclared or
  undefined.
  @return the value of the configuration property identified by name, or the default property value if the property
  was undeclared or undefined.