/** @see javax.sql.DataSource#getConnection(java.lang.String, java.lang.String) */
 public Connection getConnection(String username, String password) throws SQLException {
   Properties p = config.toProperties();
   if (username != null) p.put("user", username);
   if (password != null) p.put("pass", password);
   return JDBC.createConnection(url, p);
 }