code: public static DatabaseLiaison getLiaison (String url)
      {
          if (url == null) throw new NullPointerException("URL must not be null");
          // see if we already have a liaison mapped for this connection
          DatabaseLiaison liaison = _mappings.get(url);
          if (liaison == null) {
              // scan the list looking for a matching liaison
              for (DatabaseLiaison candidate : _liaisons) {
                  if (candidate.matchesURL(url)) {
                      liaison = candidate;
                      break;
                  }
              }
  
              // if we didn't find a matching liaison, use the default
              if (liaison == null) {
                  log.warning("Unable to match liaison for database. Using default.", "url", url);
                  liaison = new DefaultLiaison();
              }
  
              // map this URL to this liaison
              _mappings.put(url, liaison);
          }
  
          return liaison;
      }
docs: Fetch the appropriate database liaison for the supplied URL, which should be the same string
  that would be used to configure a connection to the database.