JPA persist foreign key restriction violation - jpa

Question

I have a problem with persisting new objects to the database. I'm using Eclipselink and Postgresql. When I'm trying to add a new Merchandise, cascade adds also Price object.
Price.java
#Entity
#Table(name = "Prices")
public class Price implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(updatable = false)
private int id;
#Column(updatable = false, nullable = false)
private float value;
#Column(updatable = false, nullable = false)
private Date startDate;
#Column(updatable = false, nullable = true)
private Date endDate;
#ManyToOne(targetEntity=Merchandise.class,cascade=CascadeType.ALL)
#JoinColumn(name="id",nullable = false,updatable = false,insertable=false)
private Merchandise merchandiseId;
#Column(updatable = false, nullable = true)
private float valueBulk;
#Column(updatable = false, nullable = true)
private float valueRetail;
#Column(updatable = false, nullable = true)
private float makeupPercent;
#Column(updatable = false, nullable = true)
private float makeupForce;
Merchandise.java
#Entity
#Table(name="Merchandises")
public class Merchandise implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(updatable = false)
private int id;
#Column(updatable = false)
private int externalId;
#Column(unique = false, nullable = false, updatable = true)
private String name;
#Column(unique = false, nullable = true, updatable = true)
private int available;
#Column(unique = false, nullable = true, updatable = true)
private String description;
#OneToMany(targetEntity = Price.class, mappedBy = "merchandiseId",cascade = CascadeType.PERSIST)
private List<Price> prices;
#OneToMany(targetEntity = MerchandiseCategory.class, mappedBy = "merchandiseId",cascade = CascadeType.PERSIST)
private List<MerchandiseCategory> merchandiseCategories;
#OneToMany(targetEntity = MerchandiseOrder.class, mappedBy = "merchandiseId",cascade=CascadeType.PERSIST)
private List<MerchandiseOrder> merchandiseOrders;
#OneToMany(targetEntity = MerchandiseDiscount.class, mappedBy = "merchandiseId",cascade=CascadeType.PERSIST) //#61
private List<MerchandiseDiscount> discounts; //#61
my code in facede looks like this:
Dao dao = new DAO();//begins transaction etc.
Merchandise m = new Merchandise;
m.set..//setting all needed fields
List<Price> list = new ArrayList<Price>();
Price p = new Price();
p.set..//setting all needed fields
p.setMerchandiseID(m);
list.add(p);
m.setPrices(list);
dao.addMerchandise(m);//persisting
This gets mean error (in Polish base so I'll try to translate it): foreign key restriction violation - Key (id)=(356) is not present in merchandises.
I think this is problem with generating id, id fiels is always replaced by generated id, and i think they are different, but in this case should be the same

Answer 1

Your Price class uses its "id" field as the as the foreign key to Merchandise. You have also marked the ID attribute mapping to be generated, so it will always be different than what is in Merchandise. Did you intend Price to use its foreign key to Merchandise as the primary key? If so, you need to remove the #GeneratedValue from Price and either
1) need to persist Merchandise first, flush so that its primary key is assigned, and then set the value into p.setId() as well as calling p.setMerchandiseID(m).
or
2) use JPA 2.0's derived ID capability and mark Price's merchandiseId attribute as either #Id (and remove the int id as it isn't needed), or use #MapsId. #Mapsid will allow JPA to set the id value from Merchandise automatically when it is assigned a value.
Some info: http://wiki.eclipse.org/EclipseLink/Examples/JPA/2.0/DerivedIdentifiers
http://wiki.eclipse.org/EclipseLink/Development/JPA_2.0/mappedbyid
If you meant for Price to have its own independent primary key, you need to add a foreign key in the price table:
#ManyToOne(targetEntity=Merchandise.class,cascade=CascadeType.ALL)
#JoinColumn(name="fk_merchandiseid",nullable = false)
private Merchandise merchandiseId;