其实我们没注意

 //返回自增长id
 public static <T> int insertNo(String sql, T bean,
   StatementMapper<T> mapper) {
  Connection conn = null;
  PreparedStatement stmt = null;
  ResultSet rs = null;
  int updNum = 0;
  try {
   conn = getConn();
   stmt = conn.prepareStatement(sql, stmt.RETURN_GENERATED_KEYS);//插入行并返回键值
   mapper.mapStatement(stmt, bean);
   updNum = stmt.executeUpdate();
   rs = stmt.getGeneratedKeys();//得到生成的键值
   if(rs.next()) {
    updNum = rs.getInt(1);
   }
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   DbUtils.closeQuietly(rs);
   DbUtils.closeQuietly(stmt);
   DbUtils.closeQuietly(conn);
  }
  return updNum;
 }

通用方案