Can't save a OneToMany/ManyToOne relationship in Spring Data REST request - spring

Question

I am using Spring Data JPA and Spring Data Rest.
When making a REST request to persist an entity, I get the next error:
org.springframework.dao.DataIntegrityViolationException: not-null property references a null or transient value
My data model has the following entities:
Contract:
#Entity
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING)
public class Contract implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToMany(
cascade = CascadeType.ALL,
orphanRemoval = true,
fetch = FetchType.LAZY,
mappedBy="contract"
)
private List<Participation> participants = new ArrayList<Participation>();
private String name;
}
Participation:
#Entity
public class Participation implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(nullable = false) //By default the column will be CONTRACT_ID
private Contract contract;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(nullable = false)
private Contact contact;
private String clauses;
}
Contact:
#Entity
public class Contact implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String emailAddress;
}
I have 2 JPARepositories:
public interface ContractRepository extends JpaRepository<Contract, Long> {
List<Contract> findByNameContainsIgnoreCase(String name);
}
public interface ContactRepository extends JpaRepository<Contact, Long> {
}
To save a new Contract with a couple of participations, I am doing the next steps in Postman:
Create a Contract and get its href:
Request: POST http://localhost:8080/api/contracts
Body:
{
"name": "Contract1"
}
The response is successful:
201 Created
{
"name": "Contract1",
"participants": [],
"_links": {
"self": {
"href": "http://localhost:8080/api/contracts/4"
},
"contract": {
"href": "http://localhost:8080/api/contracts/4"
},
}
}
So far so good. Now that I have the contract persisted, I am adding participants:
Contact 1 already exists in the data base.
Request: PATCH http://localhost:8080/api/contracts/4
Body:
{
"participants": [
{
"clauses": "Bla bla bla",
"contact": {
"href": "http://localhost:8080/api/contacts/1"
},
"contract": {
"href": "http://localhost:8080/api/contracts/4"
}
}
]
}
When executing this request the system complains on the field/fk contract:
{
"cause": {
"cause": null,
"message": "not-null property references a null or transient value : com.xxx.xxx.model.Participation.contract"
},
"message": "not-null property references a null or transient value : com.xxx.xxx.model.Participation.contract; nested exception is org.hibernate.PropertyValueException: not-null property references a null or transient value : com.xxx.xxx.model.Participation.contract"
}
I tried several ways to reference the contract in the participation, like:
"contract": "http://localhost:8080/api/contracts/4"
No luck. For some reason the system is leaving the field empty instead of using the foreing key of the entity created in step 1.
What am I doing wrong?

Answer 1

The problem can be solved by:
Add a new repository ParticipationRepository (extends JpaRepository);
Create first a Contract without Participations:
POST http://localhost:8080/api/contracts { "name": "Contract1" }
Response:
201 Created
{
"name": "Contract1",
"_links": {
"self": {
"href": "http://localhost:8080/api/contracts/3"
},
"contract": {
"href": "http://localhost:8080/api/contracts/3"
},
"participants": {
"href": "http://localhost:8080/api/contracts/3/participants"
}
}
}
Create a Participation and use the URI from the just created Contract to set the FK. Assume Contact 1 already exists in the Data Base.
POST http://localhost:8080/api/participations {
"clauses": "bla, bla, bla",
"contract": "http://localhost:8080/api/contracts/3",
"contact": "http://localhost:8080/api/contacts/1" }
Response:
201 Created
{
"clauses": "bla, bla, bla",
"_links": {
"self": {
"href": "http://localhost:8080/api/participations/5"
},
"participation": {
"href": "http://localhost:8080/api/participations/5"
},
"contract": {
"href": "http://localhost:8080/api/participations/5/contract"
},
"contact": {
"href": "http://localhost:8080/api/contacts/5/contact"
}
}
}