Jpa disable auto save

Question

I am using JPA eclipse Toplink and EJB

every time I get an entity from a database, then change some data inside it,

Database

(MYSQL) automatically changes as well if I don’t do or do something.

Example:

Player p = em.findById(1);
p.setName(newName);
// i do nothing , but database automaticly change

I already read the question related to this, but I still can not figure it out

I think I need to detach the object, but I don’t know how to do it, because

I have a GenericDAO class created from netbeans

GenericDAO (generated from netbeans)

public abstract class GenericDAO<T> {
    private Class<T> entityClass;

    public GenericDAO(Class<T> entityClass) {
        this.entityClass = entityClass;
    }

    protected abstract EntityManager getEntityManager();

    public void insert(T entity) {
        getEntityManager().persist(entity);
    }

    public void edit(T entity) {
        getEntityManager().merge(entity);
    }

    public void delete(T entity) {
        getEntityManager().remove(getEntityManager().merge(entity));
    }

    public T findById(Object id) {
        return getEntityManager().find(entityClass, id);
    }

    public List<T> findAll() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        return getEntityManager().createQuery(cq).getResultList();
    }

    public List<T> findRange(int[] range) {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        q.setMaxResults(range[1] - range[0] + 1);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }

    public int count() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
        cq.select(getEntityManager().getCriteriaBuilder().count(rt));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        return ((Long) q.getSingleResult()).intValue();
    }

}

Daoplayer

@Local
public interface DaoPlayer{
    void insert(Player player);

    void edit(Player player);

    void delete(Player player);

    Player findById(Object id);

    List<Player> findAll();

    List<Player> findRange(int[] range);

    int count();

Impplayer

@Stateless
public class ImplPlayer extends GenericDAO<Player> implements DaoPlayer{
    @PersistenceContext(unitName = "MonsterPuzzle")
    private EntityManager em;

    @Override
    protected EntityManager getEntityManager() {
        return em;
    }

    public ImplPlayer() {
        super(Player.class);
    }

}

My question

• how to disable jpa automatically save to database?
• (Because I think I need to disconnect), how to separate an object from GenericDAO?

Answer 1

, . :

Player findById(Object id){}

Java EE, , DAO.

@TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
Player findById(Object id) {}

, , . , , .

Answer 2

: " ".

? , , EntityManager : persist, merge, refresh, delete (, ) (JPQL find) .

:

entityManager.getTransaction().begin();
Dog dog = entityManager.find(Dog.class, 1);
dog.setGoodBoyLevel(99);
entityManager.getTransaction().commit();

, find , .

EJB, , . REQUIRED : , . , . ( )

- , . ? NOT_SUPPORTED:

@TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
public void yourMethod(){
    // to awesome things
}

NOT_SUPPORTED, . ? JPA . , . :

entityManager.getTransaction().begin();
Dog dog = new Dog();
Owner owner = getDetachedOwner(ownerId);
dog.setOwner(owner);
entityManager.persist(dog);
entityManager.getTransaction().commit();

, , JPA .

NOT_SUPPORTED. [=