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.

Just a side note, it's better to remove @Transactional from your repository interfaces, first, because it's an interface, second, because the service layer should be the master of transaction. On a custom repo implementation, I would suggest to use @Transactional(propagation=SUPPORTS) to enable non-transactional reads if needed to better performance. See stackoverflow.com/questions/3120143/… — Andrey Usov
– Andrey Usov, Commented Oct 28, 2015 at 23:25

Andrey Usov · Accepted Answer · 2015-10-28 23:18:49Z

Just another workaround using a RelProvider:

Do not use @JsonTypeInfo

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:

It seems like RelProvider -> LinkRelationProvider: docs.spring.io/spring-hateoas/docs/current/api/org/…. I'm not going to edit this answer though since I'm not 100% certain.

a better oliver · Accepted Answer · 2015-03-14 19:14:40Z

It looks like a Jackson problem. To be specific, it's the following code in com.fasterxml.jackson.databind.deser.SettableBeanProperty:

if (_valueTypeDeserializer != null) { return _valueDeserializer.deserializeWithType(jp, ctxt, _valueTypeDeserializer); } return _valueDeserializer.deserialize(jp, ctxt);

Without inheritance _valueDeserializer.deserialize would be called which in turn runs some Spring code to convert the URI to a Supporter.

With inheritance _valueDeserializer.deserializeWithType is called and vanilla Jackson, of course, expects an object, not a URI.

If supporter was nullable you could first POST to /contacts and then PUT the supporter's URI to /contacts/xx/supporter. Unfortunately I am not aware of any other solution.

I do not think it's Jackson issue. Good old Jackson works just fine. It's an issue with a custom Jackson URL serialiser from Spring DATA REST. Seems like this use-case is just not covered yet but there're workarounds.
@aux The problem occurs while deserializing the request body, so what exactly's got the "custom Jackson URL serialiser" to do with that?
Sorry, my misspelling, i meant deserializer, of course. By the way, this is already fixed in Spring Data REST 2.4 - see jira.spring.io/browse/DATAREST-662

Ivelin Velkov · Accepted Answer · 2015-10-04 20:41:04Z

You should be able to workaround this by setting @JsonTypeInfo(use= JsonTypeInfo.Id.NONE) at the property/method level e.g.

Try with this:

@ManyToOne // same error with @OneToOne @JoinColumn(name = "supporter_id", referencedColumnName = "id", nullable = false) @JsonTypeInfo(use= JsonTypeInfo.Id.NONE) public SupporterEntity getSupporter() { return supporter; }

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

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