archaius-core/src/main/java/com/netflix/config/DynamicPropertyFactory.java
public DynamicStringProperty getStringProperty(String propName, String defaultValue) {
        return getStringProperty(propName, defaultValue, null);
    }
public DynamicStringProperty getStringProperty(String propName, String defaultValue) {
        return getStringProperty(propName, defaultValue, null);
    }
Create a new property whose value is a string and subject to change on-the-fly.

@param propName     property name
@param defaultValue default value if the property is not defined in underlying configuration