org.hibernate.SessionException: Session is closed! error

Question

I am deleting an object by passing id but it gets deleted but shows "session is closed" error. I have just posted this two classes one is controller and another is delete method where the object gets deleted but says "session is closed".

 In CategoryDAOImpl.java class

        /*
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        package com.acem.sp.dao.impl;

        import com.acem.sp.dao.CategoryDAO;
        import com.acem.sp.entity.Category;
        import java.util.List;
        import org.hibernate.Query;
        import org.hibernate.Session;
        import org.hibernate.SessionFactory;
        import org.hibernate.Transaction;
        import org.springframework.beans.factory.annotation.Autowired;


        import org.springframework.stereotype.Repository;

        /**
         *
         * @author AshwinKArki
         */
        @Repository
        public class CategoryDAOImpl implements CategoryDAO {

           @Autowired
            private SessionFactory sessionFactory;

            private Session session;

            private Transaction trans;
            @Override
            public List<Category> getAll() {
              session=sessionFactory.openSession();
            Query query=session.getNamedQuery("Category.findAll");
           List<Category> catList=query.list();
            session.close();
            return catList;
            }

            @Override
            public Category getById(int id) {
               session=sessionFactory.openSession();
          Category cat=(Category)session.get(Category.class, id);
           session.close();
            return cat;
                 }


            @Override
            public void insert(Category t) {
              session=sessionFactory.openSession();

                trans=session.beginTransaction();

                session.save(t);
                trans.commit();
                session.close();
            }

            @Override
            public void update(Category t) {
                session=sessionFactory.openSession();

                trans=session.beginTransaction();

                session.saveOrUpdate(t);
                trans.commit();
               session.close(); 
            }

            @Override
            public void delete(int id) {
               session = session.getSessionFactory().openSession();
                trans=session.beginTransaction();

             session.delete(getById(id));
             trans.commit();
              session.flush() ;
             session.close();


            }

        }
        In my admincontroller.java class

         @RequestMapping(value="/dashboard/delete/{id}",method=RequestMethod.GET)
            public String delete(@PathVariable("id") int id){
               categoryDAO.delete(id);
                return "admin/dashboard";
            }
        }

Answer 1

You can use @Transactional annotation to the methods that need a session

Like this:

   @Override
   @Transactional
   public void delete(int id) {
      session = session.getSessionFactory().openSession();
      trans=session.beginTransaction();

      session.delete(getById(id));
      trans.commit();
      session.flush() ;
      session.close();

        }

Answer 2

On this line:

session.delete(getById(id));

Inside the getById, you are closing the session and when you do the delete the session is already closed (in theory the openSession creates a new session but, there is already one in the current transaction, so i guess it is reusing the parent one).

A solution would be to create an overloaded getById method to which you can pass an already existing session and work on that:

@Override
public Category getById(int id, Session session) {

     Category cat=(Category)session.get(Category.class, id);

     return cat;
}

And in the delete you would:

@Override
public void delete(int id) {
      session = session.getSessionFactory().openSession();
      trans=session.beginTransaction();

      session.delete(getById(id, session));
      trans.commit();
      session.flush() ;
      session.close();
}