Display data from database using hibernate

Question

I am new in hibernate and I am struggling with a problem. I want to display a list of objects to a .XHTML page using JSF. But I don't know why, I lose the data on the way. Even though the method from DAO returns a list of objects from database (I saw it by doing debug) when I try to assign that list to a list of users from another class I loose that data and the list from DAO becomes null. So there are no results in GUI from my datatable.

public class UsersBean {

        private List<User> allUsers;

        public UsersBean() {
        init();
        }

        private void init() {
        UsersController.doInitialise(allUsers);
        }

  // getters, setters

    }


public class UsersController {

    public static void doInitialise(List<User> users) {

    users = new ArrayList<User>();
    UserDao userDao = new UserDaoImpl();
    users = userDao.getAllEnities();
    System.out.println(users.toString());
    }

}

public class UserDaoImpl{

    @Override
    public List<User> getAllEnities() {

    List<User> users= null;
    Session session = null;
    Transaction transaction = null;
    try {
        session = sessionFactory.openSession();
        transaction = session.beginTransaction();
        org.hibernate.query.Query query = session.createQuery("from User");
        users= query.list();
        transaction.commit();
    }  finally {
        session.close();
    }
    return users;
    }

}

I would assume it could be because you're closing the session. Once you close the session all the references to those objects become null. With Hibernate you generally keep a single session open until you're done with the objects that are cached in that session. Usually a single session is enough for most applications. — Jason
– Jason, Commented Mar 6, 2020 at 13:44

Arnaud · Accepted Answer · 2020-03-06 13:50:43Z

2

If you want to modify the content of the original list, don't assign another list object to it, this will have no effect.

Instead, just alter the content directly, i.e :

public static void doInitialise(List<User> users) {

UserDao userDao = new UserDaoImpl();
users.addAll(userDao.getAllEnities());
System.out.println(users.toString());

}

answered Mar 6, 2020 at 13:50

Arnaud

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Comments

Alexandru Somai · Accepted Answer · 2020-03-06 13:51:30Z

1

You are not assigning the value of allUsers into your UsersBean, probably that's why is not working. To have it working, refactor the doInitialise to return a List<User>, then, in the UsersBean, just assign the users.

class UsersBean {

    private List<User> allUsers;

    public UsersBean() {
        init();
    }

    private void init() {
        this.allUsers = UsersController.doInitialise();
    }
}

public class UsersController {

    public static List<User> doInitialise() {
        UserDao userDao = new UserDaoImpl();

        return userDao.getAllEnities();
    }
}

edited Mar 6, 2020 at 13:51

answered Mar 6, 2020 at 13:46

Alexandru Somai

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