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JPA: Reference column in the child entity is null when using unidirectional #OneToMany

I have two entity classes.
Order.java
#Entity
#Table(name = "order_table")
public class Order implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Long id;
#Column(name = "name")
private String name;
#OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval = true)
#JoinColumn(name = "order_id", referencedColumnName = "id", nullable = false, insertable=false, updatable=false)
private Set<Item> items;
// getters & setters & toString
Item.java
#Entity
#Table(name = "item")
public class Item implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Long id;
#Column(name = "name")
private String name;
#Column(name = "order_id", nullable = false)
private Long orderId;
// getters & setters && toString
I created a test class like this:
#Test
public void createOrderWithItems() {
Item item = new Item();
item.setName("Iron Man");
Order order = new Order();
order.setName("Toy");
order.getItems().add(item);
Order created = service.createOrder(order);
Order orderById = service.getOrderById(order.getId());
System.out.println("Created Order: " + orderById);
Item itemById = service.getItemById(item.getId());
System.out.println("Created item: " + itemById);
Assert.notNull(created.getId(), "Order ID is Null");
}
Test is green but if you check output, you'll see that orderId field in the Item class is null.
Created Order: Order{id=1, name='Toy', items=[Item{id=2, name='Iron Man', orderId=null}]}
Created item: Item{id=2, name='Iron Man', orderId=null}
Does JPA not update this column in the db automatically? Is this column is redundant? If so, how can I retrieve this information from test code?

You need to set orderId explicitly.
item.setOrderId(order.getId());
order.getItems().add(item);
You can create a method addItem(Item item) in your Order class and hide this logic within it.
Cascading will create an entry in db but it won't initialize field. JPA annotations just indicate to JPA provider how to perform mapping between entity and table.
Moreover, check your annotations. #JoinColumn should be used in the entity which owns the relationship (the corresponding table has column as a foreign key). Check the top answer for this question for detailed explanations: What's the difference between #JoinColumn and mappedBy when using a JPA #OneToMany association

Cascade persist creates duplicate rows?

I'm creating a database entity object Order, and assign it to multiple entities of type BookingCode.
Problem: this creates a single order in db, which is fine. But the order itself has a #OneToOne OrderDescription, which occurs duplicate in the database.
#Entity
public class BookingCode {
#Id
private Long id;
#ManyToOne(cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH, CascadeType.DETACH})
private Order order;
}
#Entity
public class Order {
#Id
private Long id;
private String orderName;
#OneToOne(mappedBy = "order", cascade = CascadeType.ALL, orphanRemoval = true)
private OrderDescription description;
}
#Entity
public class OrderDescription {
#Id
private Long id;
//for simplicity just one text element; of course multiple fields in real life
private String text;
#OneToOne
private Order order;
}
Test:
Order order = new Order();
order.setOrderName("test");
OrderDescription d = new OrderDescription("testdescr");
d.setOrder(order);
order.setDescription(d);
List<BookingCodes> codes = new ArrayList<>();
BookingCode code = new BookingCode();
code.setOrder(order);
codes.add(order);
BookingCode code2 = new BookingCode();
code2.setOrder(order); //using the same offer entity!
codes.add(order2);
codes = dao.save(codes); //CrudRepository from Spring
dao.findOne(codes.get(0).getId()); //this works, find an order which has one of the OrderDescriptions
Result:
In my database I then have two OrderDescription entries, where I would expect only one, because I reused the same Order object and assigned it to different BookingCode objects.
Like:
table order_descrption:
1;"de";"testdescr";"123456"
2;"de";"testdescr";"123456"
As Order has a #OneToOne relation to OrderDescription
And I even don't understand why the select using findOne() works correctly. Because in database I now have two OrderDescriptions that map to the same Order, but an Order can only have one of them.

Persist the order first and then assign it to both bookingCode .

I had a similar issue where I had an Order obj and its variable prevOrder was referring to itself i.e. Order entity. And when I stored order, it would end up storing duplicate records for prevOrder.
I had the following code:
#Entity
#Table(name = "orders")
public class Order implements Serializable {
#Id
#GeneratedValue(generator = "order_id_generator")
#SequenceGenerator(name = "order_id_generator", sequenceName = "order_id_sequence", allocationSize = 1)
#Column(name = "id", updatable = false, nullable = false)
private Long id;
#OneToOne(cascade = CascadeType.ALL, optional = true)
#JoinColumn(name = "previous_order_id", unique = true, updatable = false, referencedColumnName = "id")
private Order previousOrder;
#OneToOne(cascade = CascadeType.ALL, mappedBy = "previousOrder")
private Order nextOrder;
...
I tried various things including overriding equals and hashcode of Order, and adding a OneToOne mappedBy field 'nextOrder' etc. But noticed JPA didn't even call equals() to determine object's uniqueness. Ultimately I found out that JPA uses id field as the object's identifier and I wasn't storing the generated id while storing the object to a distrobuted cache. So it was all the time creating fresh objects during persistence.

JPA Entity field reference OneToOne recursive

I am getting this error when I will persist() my entity. I think that the cause of the error is the relation, my idea is that FolderEntity (represents a virtual folder) can be stay inside another (only one) Then I created the reference to self (In the extended class, because all resources can be inside a folder, and folder is an resource)
org.hibernate.AnnotationException: Referenced property not a (One|Many)ToOne: com.editor.entity.FolderEntity.id in mappedBy of com.editor.entity.FolderEntity.folderId
This my main Entity:
#MappedSuperclass
public abstract class Entity implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "ID", nullable = false)
private Integer id;
/** getter/setter **/
}
Then I extends it in my ResourceEntity Entity:
#MappedSuperclass
public class ResourceEntity extends Entity {
#Column(name = "NAME", length = Lengths.NAME40, unique = true, nullable = false)
private String name;
#Column(name = "DESCRIPTION", length = Lengths.DESCRIPTION1000, unique = false, nullable = true)
private String description;
#JoinColumn(name = "FOLDER_ID", updatable = true, nullable = false)
#OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "id")
private FolderEntity folderId;
/** getter/setter **/
}
Finally, I am working with this entity:
#javax.persistence.Entity
#Table(name = "EDITOR_FOLDERS")
#NamedQueries({
#NamedQuery(name = FolderEntity.ALL_FOLDERS, query = "select f from FolderEntity f"),
#NamedQuery(name = FolderEntity.FOLDER_BY_NAME, query = "select f from FolderEntity f where name = :name and resourceType = :resourceType") })
public class FolderEntity extends ResourceEntity {
public static final String ALL_FOLDERS = "findAllFolders";
public static final String FOLDER_BY_NAME = "findAllFoldersByName";
#Column(name = "RESOURCE_TYPE", length = Lengths.CODE, unique = false, nullable = false)
private Integer resourceType;
/** getter/setter **/
}
Anybodys help me to solve this? Thanks!

You should check the meaning of mappedBy: It does not reference the field that contains the ID (JPA is clever enough to find that one by itself), but it references another XToOne field that "owns" the mapping
public abstract String mappedBy
(Optional) The field that owns the relationship. This element is only specified on the inverse (non-owning) side of the association.
(from javadoc of OneToOne)
In your case you don't need the mappedBy as you are on the owning side. And you should name the attribute folder as you are referencing no ID but an entity.
Another remark: Use an enum for resourceType if you intend to define the possible values in your application as constants.

JPA mapping annotation error org.hibernate.MappingException: Foreign key must have same number of columns as the referenced primary key

I can't propper map DB tables with JPA annotation.
Tables Subject and Place is ManyToMany through JoinTable.
Subject.java
#Entity
#Table(name = "SUBJECT")
public class Subject implements Serializable {
#Id
#Column(name = "SID")
private Integer sid;
#Column(name = "NAME")
private String name;
// getters and setters
}
SubjectPlace.java
#Entity
#Table(name = "SUBJECT_PLACE")
public class SubjectPlace implements Serializable {
#Id
#Column(name = "SPID")
private Integer spid;
#ManyToOne
#JoinColumn(name = "SUB_KEY") //Subject FK
private Subject subject;
#ManyToOne
#JoinColumn(name = "PLC_KEY") //Place FK
private Place place;
// getters and setters
}
Place.java
#Entity
#Table(name = "PLACE")
public class Place implements Serializable {
#Id
#Column(name = "PID")
private Integer pid;
#Column(name = "NAME")
private String name;
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
#JoinTable(name = "SUBJECT_PLACE",
joinColumns = { #JoinColumn(name = "PLC_KEY", nullable = false, updatable = false) },
inverseJoinColumns = { #JoinColumn(name = "SUB_KEY", nullable = false, updatable = false) })
private Set<Subject> subjects;
// getters and setters
}
But than I need to link Person with Subject in selected Places. I mean that each Place has its own collection of Subject. And a Person have link to Subject whitch resides in particular Place.
like This:
Subject (M) -- (M) Place through JoinTable Subject (1) -- (M) Subject_Place (M) -- (1) Place
Person (M) -- (M) Subject_Place through JoinTable Person (1) -- (M) Person_Subject_Place (M) -- (1) Subject_Place
Person.java
#Entity
#Table(name = "PERSON")
public class Person implements Serializable {
#Id
#Column(name = "PRSID")
private Integer prsid;
#Column(name = "NAME")
private String name;
// How to annotate this code?
// I experience problem in this part of code
#OneToMany
#JoinColumn(name="SPID_KEY")
private List<SubjectPlace> subjectPlaces;
// getters and setters
}
PersonSubjectPlace.java
#Entity
#Table(name = "PERSON_SUBJECT_PLACE")
public class PersonSubjectPlace implements Serializable {
#Id
#Column(name = "PSPID") // Person_Subject_Place ID
private Integer pspid;
#ManyToOne
#JoinColumn(name = "PER_KEY") //Person FK
private Person person;
// How to annotate this code?
// I experience problem in this part of code
#ManyToOne
#JoinColumn(name = "SPID_KEY") //Subject_Place FK
private SubjectPlace subjectPlace;
// getters and setters
}
And when I try so get Persons and its Subjects, I get this error:
Caused by: org.hibernate.MappingException: Foreign key (FK2C3B79384AABC975:PERSON_SUBJECT_PLACE [SPID_KEY])) must have same number of columns as the referenced primary key (SUBJECT_PLACE [PLC_KEY,SUB_KEY])
What, How shoul I map?

In your OneToMany mapping you don't need to specify the foreign key, you just need to use mappedBy property to refer your mapping object, you can learn more about it in OneToMany Mapping Documentation, and here's what you need to map Person and PersonSubjectPlace entities:
In your Person class:
#OneToMany(mappedBy="person")
private List<PersonSubjectPlace> personsubjectPlaces;
In your PersonSubjectPlace class:
#ManyToOne
#JoinColumn(name="PRSID") //Specify the primary key of Person
private Person person;
For further information about the difference between JoinColumn and mappedBy you can take a look at this answer.
EDIT:
For the mapping between SubjectPlace and PersonSubjectPlace:
In your SubjectPlace class:
#OneToMany(mappedBy="subjectPlace")
private List<PersonSubjectPlace> personsubjectPlaces;
In your PersonSubjectPlace class:
#ManyToOne
#JoinColumn(name="SPID") //Specify the primary key of SubjectPerson
private SubjectPlace subjectPlace;
Note:
The best approach to map those classes is to use #JoinTable between Person and SubjectPlace, take a look at this #JoinTable example, because PersonSubjectPlace is pratically an asociation-entity between Person and SubjectPlace.

You should remove #Joincolumn annotation and add mappedBy variable to #OneToMany annotation.
#OneToMany(mappedBy = "spid")
You should have a variable in SubjectPlace that has a Person where you should put #JoinColumn annotation

Hibernate database mapping

Firstly, I am somewhat new with Hibernate. To get to know the technology I am using it in a project. I am trying to map the following database:
Campaign
campaignId(+)
name
Promotion
campaignId(+)
discount(+)
product
message
I've indicated the primary key in both cases with a (+). The 'campaignId' in Promotion is a foreign key to Campaign to model the 1:m mapping (A Campaign has many Promotions). Using annotations I am stuck on how to do this.
I do not really want to add a promotionId in the Promotion table as it makes working with the data cumbersome. This of course, makes the bridging table a bit tricky. I also have problems working with a foreign key that is also part of the primary key.
Is a mapping for this possible at all?
Ok, I got it working. Sort of. Have to check if persistence actually work. I did the following:
#Entity
#Table(name = "CAMPAIGNS")
#Audited
public class CampaignEntity {
private int campaignId;
private String name;
private List<PromotionEntity> promotions;
public CampaignEntity(int campaignId, String name) {
this.campaignId = campaignId;
this.name = name;
}
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "cmp_id")
public int getCampaignId() {
return campaignId;
}
public void setCampaignId(int campaignId) {
this.campaignId = campaignId;
}
// Campaign name here... left out to save space
#OneToMany
#JoinColumn(name = "cmp_id")
public List<PromotionEntity> getPromotions() {
return promotions;
}
public void setPromotions(List<PromotionEntity> promotions) {
this.promotions = promotions;
}
}
Promotion is a vanilla mapping (not using embedded after all), with the fields: campaignId, discount, message. (It also does not have a #ManyToOne annotation.)
Does that make sense?
Lastly, and this will be first prize: as you can see I'm using Envers to audit the whole thing. The above creates a rather ugly "CampaignEntity_PromotionEntity_AUD" table. I understand that it is needed, but how can I rename it to CAMPAIGN_PROMOTION_AUD rather?
Thanks guys!
I got an answer on a lonely website deeply hidden away in far-corners of the Hibernate's Jira error tracking website: https://hibernate.onjira.com/browse/HHH-3729.
The answer is to use #AuditJoinTable(name = "CAMPAIGN_PROMOTION_AUD") of course.

This is a basic example of a one-to-many relationship and its inverse.
public class Campaign
{
#OneToMany(mappedBy = "campaign)
private List<Promotion> promotions;
}
public class Promotion
{
#ManyToOne
private Campaign campaign;
}

You can use an EmbeddedId to create a multi-field PK.
Remove the PK fields from Promotion
Create a separate entity, say PromotionPK, without any annotations except for #Column on the PK fields
In Promotion, include that PK class as field, annotating it using #EmbeddedId, with getters and setters
The FK mapping is as Wouter indicated.

This is what I am now using. It works well and Hibernate handles the PKs of the Promotions for me. Thanks again.
#Entity
#Table(name = "CAMPAIGNS")
#Audited
public class CampaignEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false)
private Integer campaignId;
#Column(name = "name", nullable = false, unique = true)
private String campaignName;
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
#JoinTable(name = "CAMPAIGN_PROMOTIONS",
joinColumns = { #JoinColumn(name = "campaign_id") },
inverseJoinColumns = { #JoinColumn(name = "promotion_id") })
private Set<PromotionEntity> promotions;
...
}
and then, PromotionEntity:
#Entity
#Table(name = "PROMOTIONS")
#Audited
public class PromotionEntity implements Comparable<PromotionEntity> {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#Column(name = "discount", nullable = false)
private Integer discount;
#Column(name = "message", nullable = false)
private String message;
...
}
I also prefer annotating the fields rather than the getters as it is more compact and reads easier.