Databases
StackOverflow2013
Postsdbo
POJava EE6/EJB3/JPA2: How to add an existing (but detached) entity to a new entity in ManyToOne?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POJava EE6/EJB3/JPA2: How to add an existing (but detached) entity to a new entity in ManyToOne?
    primarykey
    data
    text
    <p>I have problems setting existing but detached entities into a ManyToOne relation, Hibernate throws a <code>PersistentObjectException</code> saying: 'detached entity passed to persist: model.persons.Customer'.</p> <p>My use case is as follows:</p> <p>I open a JSF2 view which lets me create an order through a Named bean and a call to a stateless OrderDAO EJB. On that view i can select a customer from a drop down list. The drop down list is populated using another stateless CustomerDAO EJB which fetches a list of customers from the database. I select the customer and the customer is set to the order. When i save the order using the stateless OrderDAO EJB the above mentioned exception is thrown.</p> <p>My entities looks as follows:</p> <pre><code>@Entity public class Order extends AbstractEntity implements Serializable { private static final long serialVersionUID = -8061887078955032972L; @ManyToOne(cascade={CascadeType.MERGE, CascadeType.REFRESH, CascadeType.PERSIST}, optional = false) private Customer customer = null; ... } @Entity @DiscriminatorValue("customer") public class Customer extends Person implements Serializable { private static final long serialVersionUID = 2788107135840578322L; @OneToMany(cascade=CascadeType.ALL, mappedBy="customer") private List&lt;Order&gt; orders = null; ... } </code></pre> <p>And the code involved looks as follows:</p> <pre><code>@Named @ConversationScoped public class OrderController implements Serializable { private static final long serialVersionUID = -4868506512979135651L; @EJB private OrderEJB orderBean; private Order order; ... public Order getOrder() { if (order == null) { if (id == null) { order = orderBean.create(); } else { order = orderBean.findById(id); } } return order; } public String saveOrder() { order = orderBean.save(order); return "savedOrder"; } } @Stateless public class OrderEJB extends GenericDAO&lt;Order&gt; { } public class GenericDAO&lt;T extends AbstractEntity&gt; { public T create() { try { return getClassType().newInstance(); } catch (Exception e) { logger.log(Level.SEVERE, "Error creating new instance of "+getClassType(), e); } return null; } public T save(T entity) { if (entity.getId() == null) { saveNew(entity); } else { entity = update(entity); } return entity; } private void saveNew(T entity) { em.persist(entity); } private T update(T entity) { return em.merge(entity); } } </code></pre> <p>Is the fact that i use two different EJBs, one for the order and one for the customer a problem? </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USJoysn
    1. USJoysn
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COAs i read the whole internet regarding similar topics :) might this be a usecase for statefull EJBs and PersistenceContextType.EXTENDED ?
      singulars
      1. POJava EE6/EJB3/JPA2: How to add an existing (but detached) entity to a new entity in ManyToOne?
      1. USJoysn
    2. COin GenericDAO#create it might be better to just propagate the/a exception instead of returning null. Returning nulls as a "failure value" instead of an indicator for absense of data is a bad practice (see eg Clean Code)
      singulars
      1. POJava EE6/EJB3/JPA2: How to add an existing (but detached) entity to a new entity in ManyToOne?
      1. USMike Braun
    3. COah, ok :) thanks.
      singulars
      1. POJava EE6/EJB3/JPA2: How to add an existing (but detached) entity to a new entity in ManyToOne?
      1. USJoysn
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload