code: public String getProperty(String key, String defaultValue) {
          String value = resolver.get(key);
          return (value == null) ? defaultValue : value;
      }
docs: Returns the configuration property for the given key, or the given default value.
  
  @param key
  configuration key
  @param defaultValue
  default value for key
  @return configuration value, or the default value if the key is not defined