code: protected void openConnection() throws SQLException {
          if (connection == null) {
              try {
                  Class.forName(configuration.getJdbcDriver());
              } catch (NullPointerException npe) {
                  throw new RuntimeException("error while lookup jdbc driver class. jdbc driver is not configured.", npe);
              } catch (ClassNotFoundException e) {
                  throw new RuntimeException("jdbc driver not found", e);
              }
  
              connection = DriverManager.getConnection(configuration.getJdbcUrl(), configuration.getJdbcUser(),
                      configuration.getJdbcPassword());
              connection.setAutoCommit(false);
          }
      }
docs: Establish a connection to the given database.
  
  @throws SQLException
  if a database access error occurs