发布新实体时如何在 Spring Data REST 中引用具有继承的实体？

Question

我有具有联合继承的实体：

支持者

@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;
...
}

个人支持者

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

公司支持者

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

我有另一个引用 SupporterEntity 的实体

@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;
    }
...
}

存储库

@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);
}

我使用 Spring Boot、Spring Data REST、Spring Data JPA、Hibernate、Jackson。当我尝试使用这样的发布请求创建新的 ContactEntity 时：

{
   "supporter":"/supporters/52",
   "postcode":"1111",
   "city":"Test City 1",
   "address":"Test Address 1",
   "email":"test1@email.com",
   "newsletter":true
}

我得到了这个例外：

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]

经过 2 天的调试，我找到了一种方法，但我有点猜到了。所以如果我这样发布：

{
   "supporter":{
      "supporterType":"PERSON",
      "id":"52"
   },
   "postcode":"1111",
   "city":"Test City 1",
   "address":"Test Address 1",
   "email":"test1@email.com",
   "newsletter":true
}

它有效，但我不知道为什么。另一个请求有什么问题？当引用的实体没有继承时，它在其他任何地方都可以这样工作。

Answer 1

使用RelProvider 的另一种解决方法：

1. 不要使用@JsonTypeInfo

2. 为SupporterEntity 子类创建RelProvider

   @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);
     }
   }
   

另见：

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

Answer 2

看起来像杰克逊问题。具体来说就是com.fasterxml.jackson.databind.deser.SettableBeanProperty中的如下代码：

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

如果没有继承 _valueDeserializer.deserialize 将被调用，然后运行一些 Spring 代码将 URI 转换为 Supporter。

通过继承 _valueDeserializer.deserializeWithType 被调用，而 vanilla Jackson 当然需要一个对象，而不是 URI。

如果supporter 可以为空，您可以先将POST 转换为/contacts，然后将PUT 支持者的URI 转换为/contacts/xx/supporter。不幸的是，我不知道有任何其他解决方案。

Answer 3

您应该能够通过在属性/方法级别设置 @JsonTypeInfo(use= JsonTypeInfo.Id.NONE) 来解决此问题，例如

试试这个：

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