Druid连接池线程未关闭问题

Question

每当我关闭tomcat服务器，就会出现的问题，如下图

Dao包下的stuDao类调用JDBCUtils类的查询用户信息方法，因为我有在finally里面调用了JDBCUtils.close()方法，为什么还出现线程未关闭的问题，很困惑

public class StuDao {
    Connection cn = null;
    PreparedStatement pr = null;
    ResultSet resultSet = null;
    public User selectUserBySidAndPswd(String sid, String pswd){
        User user = null;
        try {
            cn = JDBCUtils.getConnection();
            String sql = "select * from t_user where sid = ? and password = ?";
            pr = cn.prepareStatement(sql);
            pr.setString(1,sid);
            pr.setString(2,pswd);
            resultSet = pr.executeQuery();
            while(resultSet.next()){
                user = new User();
                user.setSid(resultSet.getString("sid"));
                user.setPassword(resultSet.getString("password"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JDBCUtils.close(resultSet,pr,cn);
        }
        return user;
    }
}

JDBCUtils类

druid的配置文件如下：