Quarkus Reactive with Vert.x and Hibernate Reactive / java.lang.NullPointerException: Cannot store to object array because "this.loadedState" is null - quarkus

Question

i am trying to use quarkus reactive with vert.x and hibernate reactive.
this is my pom.xml:
<quarkus-plugin.version>1.12.2.Final</quarkus-plugin.version>
and
<quarkus.platform.version>1.12.2.Final</quarkus.platform.version>
with:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-resteasy-reactive</artifactId>
</dependency>
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-resteasy-reactive-jackson</artifactId>
</dependency>
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-reactive-mysql-client</artifactId>
</dependency>
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-vertx-web</artifactId>
</dependency>
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-hibernate-reactive</artifactId>
</dependency>
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-reactive-pg-client</artifactId>
</dependency>
this is my application.properties file:
# postgres-configuration
quarkus.datasource.db-kind=postgresql
quarkus.datasource.username=partner_usr
quarkus.datasource.password=postgrespw
quarkus.datasource.reactive.url=vertx-reactive:postgres://localhost:3310/partnerdb
# test, but not working (schema's won't created)
quarkus.hibernate-orm.database.generation.create-schemas=true
# working (drop-and-create only on mysql, not on postgres)
quarkus.hibernate-orm.database.generation=drop-and-create
quarkus.hibernate-orm.log.sql=true
quarkus.http.cors=true
Then, i have following entities:
#Data
#MappedSuperclass
public abstract class IdEntity {
#Id
#SequenceGenerator(name = "entitySeq", sequenceName = "entitiy_id", allocationSize = 1, initialValue = 5)
#GeneratedValue(generator = "entitySeq", strategy = GenerationType.AUTO)
private Long id;
}
#Data
#Entity
#EqualsAndHashCode(callSuper = true)
public class Person extends IdEntity {
private String firstName;
private String lastName;
public Person() {
}
#ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Address personAddress;
}
#Data
#Entity
#EqualsAndHashCode(callSuper = true)
public class Address extends IdEntity {
private String street;
private String houseNumber;
private int postalCode;
private String city;
#OneToMany(orphanRemoval = true, mappedBy = "personAddress", fetch = FetchType.LAZY)
private List<Person> persons = new ArrayList<>();
public Address() {
}
}
Now, i am calling a reactive web-service with a reactive db access:
#Path("/person")
#ApplicationScoped
public class PersonResource {
#Inject
io.vertx.mutiny.pgclient.PgPool sqlClient;
#Inject
Mutiny.Session mutinySession;
#GET
//#Produces(MediaType.APPLICATION_JSON)
#Path("/list-persons")
#Route(path = "/list-persons", methods = HttpMethod.GET, produces = MediaType.APPLICATION_JSON)
#Transactional
public Multi<Person> listAllPersons() {
// return sqlClient.query("SELECT * FROM Person ORDER BY lastName ASC").execute()
// .onItem().transformToMulti(set -> Multi.createFrom().iterable(set))
// .onItem().transform(this::transformPersons);
return mutinySession.createQuery("SELECT f FROM Person f ORDER BY f.lastName")
.getResults().onItem().transform(this::transformObject);
}
private Person transformObject(Object f) {
return (Person)f;
}
private List<Object> transformPersons(Object f) {
final Person person = (PartnerMockEntity)f;
final List<Object> bogus = new ArrayList<>();
bogus.add(partner);
return bogus;
}
}
Exception:
Resulted in: com.fasterxml.jackson.databind.JsonMappingException: Cannot store to object array because "this.loadedState" is null (through reference chain: de.subito.model.Person["personAddress"]->de.subito.model.Address["person"])
I tried to use :
FetchType.EAGER on Address in Person
I removed the #OneToMany Relation in Address: this solves the error (yay), but the addresses won't be returned in the resulting json (id is existing, but the values are not fetched)
The questions is, how can i fetch in reactive those kind of relations without getting errors?
Or do i need a angular page in order to display this correctly?

Answer 1

Somehow i forgot about how fetchType.Lazy works.
Simply add a join fetch into the hql and everything works as expected.
SELECT p from Person p left join fetch p.personAddress
When using this query, there's no session/closed or any other exception thrown and the json result will be displayed as expected.
Additional note: in order to avoid recursive serialization, it is required to use the
#JsonManagedReference and #JsonBackReference
Annotations, depending on your needs to your relations.