JPA throws lazy loading exception even it is eager fetch - spring-boot

Question

User entity
#Entity
#Table(name = "T_USER")
public class User implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String lastName;
private String email;
//A user can be employee in many organizations so he look at the same time as many emplyee
#JsonManagedReference(value = "user-association")
#OneToMany(mappedBy = "user", fetch = FetchType.EAGER)
private Set<Association> associations;
....
Association entity
#Entity
#Table(name = "T_ASSOCIATION")
public class Association implements Serializable {
#EmbeddedId
private AssociationId associationId;
private String permission;
#ManyToOne(fetch = FetchType.LAZY)
#JsonBackReference(value = "user-association")
#JoinColumn(name = "user_id", referencedColumnName = "id", insertable = false, updatable = false)
private User user;
#ManyToOne(fetch = FetchType.LAZY)
#JsonBackReference(value = "organization-association")
#JoinColumn(name = "organization_id", referencedColumnName = "id", insertable = false, updatable = false)
private Organization organization;
POST endpoint
#PostMapping(path = "/{id}/users", consumes = MediaType.APPLICATION_JSON_VALUE)
public List<User> associateUserToOrganization(#RequestBody AssociationDTO userToOrgDTO, #PathVariable String id) {
Association association = new Association(new AssociationId(userToOrgDTO.getUserId(), userToOrgDTO.getOrganizationId()));
association.setPermission("GUEST_SET");
User userToAffect = userRepository.findById(userToOrgDTO.getUserId()).get();
Organization orgToAffect = organizationRepository.findById(userToOrgDTO.getOrganizationId()).get();
userToAffect.addAssociation(association);
orgToAffect.addAssociation(association);
organizationRepository.save(orgToAffect);
return userRepository.findAll().stream().filter(user -> !user.getAssociations().isEmpty()).collect(Collectors.toList());
}
When I add a user to the organization using POSTMAN with correct input, the famous error of serialization of lazy loading appears even I am not using fetch type Lazy
this is the error
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->jpa.workspace.manytomanyadditional.domain.User$HibernateProxy$pL9wPAuw["hibernateLazyInitializer"])
So i made the solution as it is mentioned in this exception and i put in application.properties,
spring.jackson.serialization.fail-on-empty-beans=false
and #JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) to remove it from the json
The issue is fixed sure, but why I am supposed to consider the User->associations relationship as Lazy fetching and not eager as I chose it...Is it related to #JsonManagedReference maybe?
am using spring 2.4.1 and hibernate (core 5.4.25 & annotations 5.1.2 Final)

Answer 1

Remove #JsonManagedReferenced, #JsonBackReference and add these following in your config class
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(jackson2HttpMessageConverter());
}
#Bean
public MappingJackson2HttpMessageConverter jackson2HttpMessageConverter() {
MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
converter.setObjectMapper(jacksonBuilder().build());
return converter;
}
public Jackson2ObjectMapperBuilder jacksonBuilder() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
Hibernate5Module hibernateModule = new Hibernate5Module();
hibernateModule.configure(Hibernate5Module.Feature.FORCE_LAZY_LOADING, false);
builder.modules(hibernateModule);
builder.featuresToDisable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
builder.featuresToDisable(MapperFeature.DEFAULT_VIEW_INCLUSION);
return builder;
}