这个空指针错误实在不知道如何解决了

public class BaseDAO {    private SessionFactory sessionFactory;    public SessionFactory getSessionFactory() {        return sessionFactory;    }    public void setSessionFactory(SessionFactory sessionFactory) {        this.sessionFactory = sessionFactory;    }    public Session getSession() {        Session session = sessionFactory.openSession();        return session;    }}

    public Integer countBack(int forum_id) {        Session session = getSession();        String hql = "select forum.countback from Forum forum where forum.id=?";        Query query = session.createQuery(hql);        query.setParameter(0, forum_id);        List coutbacklist = query.list();        session.close();        int coutback = (Integer) coutbacklist.get(0);        return coutback;    }

    public boolean delete(int reforum_id, int forum_id) {        try {            String hql = "delete from Reforum reforum where reforum.id="+reforum_id;            Session session = getSession();            Transaction tx = session.beginTransaction();            Query querydeleteReforum = session.createQuery(hql);            int b=querydeleteReforum.executeUpdate();            tx.commit();            session.close();            ForumDAO fdao = new ForumDAO();            int countback = fdao.countBack(forum_id);            fdao.removeCountBack(countback, forum_id);            if (b != 0) {                return true;            } else {                return false;            }        } catch (Exception e) {            e.printStackTrace();        }        return false;    }

    public void deleteReforum(int reforum_id, int forum_id) {        try {            rfdao.delete(reforum_id, forum_id);        } catch (Exception e) {            e.printStackTrace();        }    }

    public String deleteReforum() {        try {            //Map request = (Map) ActionContext.getContext().get("request");            forumservice.deleteReforum(Integer.parseInt(request.getParameter("reforum_id")),                    Integer.parseInt(request.getParameter("forum_id")));            forum_id = Integer.parseInt(request.getParameter("forum_id"));        } catch (Exception e) {            e.printStackTrace();        }        return "success";    }

    public Session getSession() {        Session session = sessionFactory.openSession();        return session;    }

public Session getSession() {System.out.println(sessionFactory==null?"true":"false");        Session session = sessionFactory.openSession();System.out.println(session==null?"true":"false");        return session;    }