Cannot create self link for class X. No persistent entity found - spring-data

Question

Getting the error in the title when using Spring Data REST. How to resolve?
Party.java:
#Entity
#Inheritance(strategy=InheritanceType.SINGLE_TABLE)
#JsonTypeInfo(use=JsonTypeInfo.Id.CLASS, property="#class")
#JsonSubTypes({ #JsonSubTypes.Type(value=Individual.class, name="Individual") })
public abstract class Party {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
protected Long id;
protected String name;
#Override
public String toString() {
return id + " " + name;
}
...getters, setters...
}
Individual.java:
#Entity
public class Individual extends Party {
private String gender;
#Override
public String toString() {
return gender + " " + super.toString();
}
...getters, setters...
}
PartyRepository.java:
public interface PartyRepository extends JpaRepository<Party,Long> {
}
If I POST, it saves to the db correctly:
POST /parties {"#class":"com.example.Individual", "name":"Neil", "gender":"MALE"}
But returns a 400 error:
{"cause":null,"message":"Cannot create self link for class com.example.Individual! No persistent entity found!"}
It looks like it's an Individual after retrieving from repository:
System.out.println(partyRepository.findOne(1L));
//output is MALE 1 Neil
Looks like Jackson can figure out that it's an individual:
System.out.println( new ObjectMapper().writeValueAsString( partyRepository.findOne(1L) ) );
//output is {"#class":"com.example.Individual", "id":1, "name":"Neil", "gender":"MALE"}
Why can SDR not figure it out?
How to fix? Preferably with XML config.
Versions:
SDR 2.2.0.RELEASE
SD JPA 1.7.0.RELEASE
Hibernate 4.3.6.Final

Answer 1

SDR repositories expect a non-abstract entity, in your case it would be Individual. You can google or search here for explaination on why SDR expects a non-abstract entity.
I tried your code myself and SDR won't even work for POST and I see below error message.
{
"cause": {
"cause": null,
"message": "Can not construct instance of com.spring.data.rest.test.Party, problem: abstract types either need to be mapped to concrete types, have custom deserializer, or be instantiated with additional type information\n at [Source: org.apache.catalina.connector.CoyoteInputStream#30217e25; line: 1, column: 1]"
},
"message": "Could not read JSON: Can not construct instance of com.spring.data.rest.test.Party, problem: abstract types either need to be mapped to concrete types, have custom deserializer, or be instantiated with additional type information\n at [Source: org.apache.catalina.connector.CoyoteInputStream#30217e25; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.spring.data.rest.test.Party, problem: abstract types either need to be mapped to concrete types, have custom deserializer, or be instantiated with additional type information\n at [Source: org.apache.catalina.connector.CoyoteInputStream#30217e25; line: 1, column: 1]"
}
I suggest you change respository from PartyRepository to IndividualRepository
public interface IndividualRepository extends JpaRepository<Individual,Long> {
}
You are seeing that error since SDR could not find a repository refering Individual while constructing links. Simply adding Individual respository and not exporting it would solve your problem.
#RepositoryRestResource(exported = false)
public interface IndividualRepository extends JpaRepository<Individual,Long> {
}