public synchronized void close() {
    resetPoolManager();
    is_closed = true;

    C3P0Registry.markClosed(this);

    if (Debug.DEBUG && Debug.TRACE == Debug.TRACE_MAX && logger.isLoggable(MLevel.FINEST)) {
      logger.log(
          MLevel.FINEST,
          this.getClass().getName()
              + '@'
              + Integer.toHexString(System.identityHashCode(this))
              + " has been closed. ",
          new Exception("DEBUG STACK TRACE for PoolBackedDataSource.close()."));
    }
  }
  public static SQLException toSQLException(String msg, String sqlState, Throwable t) {
    if (t instanceof SQLException) {
      if (Debug.DEBUG && Debug.TRACE == Debug.TRACE_MAX && logger.isLoggable(MLevel.FINER)) {
        SQLException s = (SQLException) t;
        StringBuffer tmp = new StringBuffer(255);
        tmp.append("Attempted to convert SQLException to SQLException. Leaving it alone.");
        tmp.append(" [SQLState: ");
        tmp.append(s.getSQLState());
        tmp.append("; errorCode: ");
        tmp.append(s.getErrorCode());
        tmp.append(']');
        if (msg != null) tmp.append(" Ignoring suggested message: '" + msg + "'.");
        logger.log(MLevel.FINER, tmp.toString(), t);

        SQLException s2 = s;
        while ((s2 = s2.getNextException()) != null)
          logger.log(MLevel.FINER, "Nested SQLException or SQLWarning: ", s2);
      }
      return (SQLException) t;
    } else {
      if (Debug.DEBUG) {
        // t.printStackTrace();
        if (logger.isLoggable(MLevel.FINE))
          logger.log(MLevel.FINE, "Converting Throwable to SQLException...", t);
      }

      if (msg == null)
        msg = "An SQLException was provoked by the following failure: " + t.toString();
      if (VersionUtils.isAtLeastJavaVersion14()) {
        SQLException out = new SQLException(msg);
        out.initCause(t);
        return out;
      } else
        return new SQLException(
            msg
                + System.getProperty("line.separator")
                + "[Cause: "
                + ThrowableUtils.extractStackTrace(t)
                + ']',
            sqlState);
    }
  }