How to reference an entity with inheritance in Spring Data REST when POSTing new entity?

Question

I have entities with joined inheritance:

Supporter

@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "supporterType")
@JsonSubTypes({
    @JsonSubTypes.Type(value = PersonSupporterEntity.class, name = "PERSON"),
    @JsonSubTypes.Type(value = CompanySupporterEntity.class, name = "COMPANY")
})
@DiscriminatorColumn(name="supporter_type")
@Table(name = "supporter")
public class SupporterEntity extends UpdatableEntity {
    private long id;
    private SupporterType supporterType;
    private PartnerEntity partner;
...
}

PersonSupporter

@Entity
@DiscriminatorValue("PERSON")
@Table(name = "person_supporter")
public class PersonSupporterEntity extends SupporterEntity {
...
}

CompanySupporter

@Entity
@DiscriminatorValue("COMPANY")
@Table(name = "company_supporter")
public class CompanySupporterEntity extends SupporterEntity {
...
}

I have another entity which references SupporterEntity

@Entity
@Table(name = "contact")
public class ContactEntity extends UpdatableEntity {

    private long id;
    private SupporterEntity supporter;
...
    @ManyToOne // same error with @OneToOne
    @JoinColumn(name = "supporter_id", referencedColumnName = "id", nullable = false)
    public SupporterEntity getSupporter() {
        return supporter;
    }
...
}

Repositories

@Transactional
@RepositoryRestResource(collectionResourceRel = "supporters", path = "supporters")
public interface SupporterEntityRepository extends JpaRepository<SupporterEntity, Long> {

    @Transactional(readOnly = true)
    @RestResource(path = "by-partner", rel = "by-partner")
    public Page<SupporterEntity> findByPartnerName(@Param("name") String name, Pageable pageable);
}

@Transactional
@RepositoryRestResource(collectionResourceRel = "person_supporters", path = "person_supporters")
public interface PersonSupporterEntityRepository extends JpaRepository<PersonSupporterEntity, Long> {

}

@Transactional
@RepositoryRestResource(collectionResourceRel = "company_supporters", path = "company_supporters")
public interface CompanySupporterEntityRepository extends JpaRepository<CompanySupporterEntity, Long> {

}

@Transactional
@RepositoryRestResource(collectionResourceRel = "contacts", path = "contacts")
public interface ContactEntityRepository extends JpaRepository<ContactEntity, Long> {

    @Transactional(readOnly = true)
    @RestResource(path = "by-supporter", rel = "by-supporter")
    public ContactEntity findBySupporterId(@Param("id") Long id);
}

I use Spring Boot, Spring Data REST, Spring Data JPA, Hibernate, Jackson. When I try to create a new ContactEntity with a post request like this:

{
   "supporter":"/supporters/52",
   "postcode":"1111",
   "city":"Test City 1",
   "address":"Test Address 1",
   "email":"[email protected]",
   "newsletter":true
}

I get this exception:

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Unexpected token (VALUE_STRING), expected FIELD_NAME: missing property 'supporterType' that is to contain type id  (for class com.facer.domain.supporter.SupporterEntity)
 at [Source: HttpInputOverHTTP@4321c221; line: 1, column: 2] (through reference chain: com.facer.domain.supporter.ContactEntity["supporter"])
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148) ~[jackson-databind-2.4.4.jar:2.4.4]

After 2 days of debugging I found a way, but I kinda guessed it. So if I post it like this:

{
   "supporter":{
      "supporterType":"PERSON",
      "id":"52"
   },
   "postcode":"1111",
   "city":"Test City 1",
   "address":"Test Address 1",
   "email":"[email protected]",
   "newsletter":true
}

It works, but I don't know why. What's wrong with the other request? It works like that everywhere else when the referenced entity does not have inheritance.

Answer 1

Just another workaround using a RelProvider:

1. Do not use @JsonTypeInfo

2. Create a RelProvider for SupporterEntity sub-classes

   @Component
   @Order(Ordered.HIGHEST_PRECEDENCE)
   public class SupporterEntityRelProvider implements RelProvider {
   
     @Override
     public String getCollectionResourceRelFor(final Class<?> type) {
       return "supporters";
     }
   
     @Override
     public String getItemResourceRelFor(final Class<?> type) {
       return "supporter";
     }
   
     @Override
     public boolean supports(final Class<?> delimiter) {
       return org.apache.commons.lang3.ClassUtils.isAssignable(delimiter, SupporterEntity.class);
     }
   }
   

See also:

• https://jira.spring.io/browse/DATAREST-344
• http://docs.spring.io/spring-hateoas/docs/current/reference/html/#configuration.at-enable