Question

Hello everyone here is my DAO class :

public class UsersDAO extends HibernateDaoSupport {

    private static final Log log = LogFactory.getLog(UsersDAO.class);

    protected void initDao() {
        //do nothing
    }

    public void save(User transientInstance) {
        log.debug("saving Users instance");
        try {
            getHibernateTemplate().saveOrUpdate(transientInstance);
            log.debug("save successful");
        } catch (RuntimeException re) {
            log.error("save failed", re);
            throw re;
        }
    }

public void update(User transientInstance) {
        log.debug("updating User instance");
        try {
            getHibernateTemplate().update(transientInstance);
            log.debug("update successful");
        } catch (RuntimeException re) {
            log.error("update failed", re);
            throw re;
        }
    }

    public void delete(User persistentInstance) {
        log.debug("deleting Users instance");
        try {
            getHibernateTemplate().delete(persistentInstance);
            log.debug("delete successful");
        } catch (RuntimeException re) {
            log.error("delete failed", re);
            throw re;
        }
    }

    public User findById( java.lang.Integer id) {
        log.debug("getting Users instance with id: " + id);
        try {
            User instance = (User) getHibernateTemplate()
                    .get("project.hibernate.Users", id);
            return instance;
        } catch (RuntimeException re) {
            log.error("get failed", re);
            throw re;
        }
    }

}

Now I wrote a test class(not a junit test) to test is everything working, my user has these fields in the database : userID which is 5characters long string and unique/primary key, and fields such as address, dob etc(total 15 columns in database table). Now in my test class I intanciated User added the values like :

User user = new User;
user.setAddress("some address");

and so I did for all 15 fields, than at the end of assigning data to User object I called in DAO to save that to database UsersDao.save(user); and save works just perfectly. My question is how do I update/delete users using the same logic?

Fox example I tried this(to delete user from table users):

User user = new User;
user.setUserID("1s54f"); // which is unique key for users no two keys are the same
UsersDao.delete(user); 

I wanted to delete user with this key but its obviously different can someone explain please how to do these. thank you

UPDATE :

Do I need to set all 15 fields on User object to delete it like I did with save method ?

Answer 1

Having not looked at Hibernate for quite a while now, I can only hazard a guess at the problem.

It seems that you are creating a User object, but only populating the User ID field, so the persistence layer knows nothing about the actual User.

I would recommend using a retrieve function that can find the User with the given ID, and then pass that User into the delete method.

User u = UsersDao.findById("1s54f");
UsersDao.delete(u);

This should work, as the persistence layer will know about the User, so it has all of the details it needs to perform the delete.

However, a more efficient method would be to find a way of deleting a user by ID, so you do not have to query the database to get the instance of the User and then delete it.

Hope this helps.

Chris