#OneToMany #ManyToOne bidirectional Entity won't accept new entity properly (GlassFish) - jpa

Question

the old issue description is obsolete
#unwichtich thank you for your tip, it helped get rid of that nasty error.
I have the entities:
#Entity
#XmlRootElement
#Table(name="WAITERENTITY")
public class WaiterEntity implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
#OneToMany(cascade = CascadeType.ALL, orphanRemoval=true, fetch = FetchType.EAGER)
#JoinColumn(name = "waiter_id")
private List<OrderEntity> orders = new ArrayList<>();
{plus usual setters and getters}
}
and
#Entity
#XmlRootElement
#Table(name="ORDERENTITY")
public class OrderEntity implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long orderNumber;
#ManyToOne (cascade = CascadeType.ALL)
#JoinColumn (name = "table_id")
private TableEntity table_;
private int sumOfMoney = 0;
private boolean finalized = false;
#OneToMany(cascade = CascadeType.ALL, orphanRemoval=true, fetch = FetchType.LAZY)
#JoinColumn(name = "order_id")
private List<OrderItemEntity> orderItems = new ArrayList<>();
#ManyToOne (cascade = CascadeType.ALL)
#JoinColumn (name = "waiter_id")
private WaiterEntity waiter;
{plus usual setters and getters}
}
But the main problem remains. In the database, everything is as it should be:
<waiterEntities>
<waiterEntity>
<id>9</id>
<name>Jack Marston #499</name>
</waiterEntity>
<waiterEntity>
<id>10</id>
<name>Abigail Marston</name>
</waiterEntity>
</waiterEntities>
<orderEntities>
<orderEntity>
<finalized>false</finalized>
<orderNumber>12</orderNumber>
<sumOfMoney>0</sumOfMoney>
<waiter>
<id>9</id>
<name>Jack Marston #499</name>
</waiter>
</orderEntity>
</orderEntities>
But the #OneToMany relation of WaiterEntity does only return an empty list when waiter.getOrders() is called.
The method that creates a new OrderEntity is the following:
public void create(OrderEntity e) {
WaiterEntity waiter = em.find(WaiterEntity.class, e.getWaiter().getId());
if (waiter != null) {
(1) e.setWaiter(waiter);
em.persist(e);
System.out.println("after persist:\n" + e);
(2) //waiter.getOrders().add(e);
(3) //em.merge(waiter);
}
}
Edit: I observed very strange behaviour. Firstly, if the lines marked with (2) and (3) are un-commented, no OrderEntity will be persisted at all. Secondly, only the following outside statements will suffice GlassFish to persist an OrderEntity:
WaiterBean waiter = client.findByNameSingle(WaiterBean.class, "John Marston");
client.create(new OrderBean(waiter));
Where create will get an unique id of the respective WaiterEntity from the database. On the other hand, an OrderEntity will be not persisted, if no WaiterEntity id is known, as in for example:
client.create(new OrderBean(new WaiterBean("Hans")));
because this new object is not obtained from the database. The strage behaviour appears, when line marked with (1) is commented out: the first statement, with the previous obtainment of the respective WaiterEntity from the database won't work, but the second statement, that doesn't obtain any WaiterEntity from the database, will work and create an OrderEntity entry in the database. I really have a hard time understanding that.
The two commented lines (2) and (3) should assure that the WaiterEntity knows its OrderEntitys for later retrieval. But the only thing that these two lines do (or one of them, i tried that as well) is preventing any OrderEntity to be persisted into the database. It just won't do anything, and no further errors are reported, which drives me nuts...
Any ideas? Thanks in advance!

Answer 1

Just a quick guess is that you are adding the wrong OrderEntity instance. If you pass an entity instance to em.merge() the EntityManager creates a new instance of your entity, copies the state from the supplied entity, and makes the new copy managed. You have to use the new copy in any further actions regarding this entity.
In code:
public void create(OrderEntity e) {
WaiterEntity waiter = em.find(WaiterEntity.class, e.getWaiter().getId());
e = em.merge(e);
if (waiter != null) waiter.getOrders().add(e);
}