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How to handle #JsonManagedReference and #JsonBackReference for three connected tables

I am stuck on given scenario:
There are three entity
a) Bill (many to one relationship with vendor) [bi-directional]
b) Vendor (one to many relationship with both vendor and vendorbank)
c) VendorBank (many to one relationship with vendor)[uni-directional]
Bills : Showing limited fields
#Entity
#Getter
#Setter
#ToString
#NoArgsConstructor
#Table(name="bill_details")
public class Bills {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="bill_id")
private int bill_id;
#Column(name="bill_no")
private String billno;
#ManyToOne(cascade = {CascadeType.MERGE})
#JoinColumn(name="b_vendor_id")
private Vendors vendors;
/* Args contructor code here */
#JsonManagedReference
public Vendors getVendors() { return vendors; }
VendorBank:Showing limited fields
public class VendorBank {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="v_bank_id")
private int vendorBankId;
#Column(name="v_acc_no")
private String accountNumber;
#Column(name="v_vendor_id")
private int vendor_id;
/*Both constructor code here*/
}
Vendor Class:Showing imp fields only
/*Lombok code here*/
public class Vendors {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="vendor_id")
private int vendor_id;
#Column(name="vendor_name")
private String vendor_name;
#OneToMany(fetch = FetchType.LAZY,cascade = CascadeType.ALL)
#JoinColumn(name="v_vendor_id")
private List<VendorBank> vendorBank;
#OneToMany(mappedBy = "vendors",cascade = {CascadeType.DETACH,CascadeType.MERGE,
CascadeType.PERSIST,CascadeType.REFRESH})
private List<Bills> bills;
#JsonBackReference
public List<Bills> getBills() {
return bills;
}
//#JsonManagedReference()
// #JsonIgnore
public List<VendorBank> getVendorBank() {
return vendorBank;
}
Output:
{
"bill_id": 102,
"billno": "B-858",
"vendors": {
"vendor_id": 3,
"vendor_name": "ABC Company",
"vendorBank": [
{
"vendorBankId": 14,
"accountNumber": "502998745002",
"vendor_id": 3
}
]
}
}
1.When I call vendor endpoint I get data from vendor + vendor bank as desired.
2.But When I call the Bill endpoints then I get data from Bill + vendor + vendorbank as above. I don't want vendor bank to come.[If I use JsonIgnore on vendorbank then i get the correct output but then above point 1 goes wrong]

OK, so what you want to achieve is to include some data from the entity in one context and not include it in another context.
I don't think you can do this by using purely annotations you put on entities, since they don't have the calling context.
So, what can we do here ?
We can use Jackson Mixins. For example:
class YourClass {
public int ignoreThis() { return 0; }
}
With this Mixin
abstract class MixIn {
#JsonIgnore abstract int ignoreThis(); // we don't need it!
}
With this:
objectMapper.getSerializationConfig().addMixInAnnotations(YourClass.class, MixIn.class)
And you can then use this to serialize the object into json in your controller (where you get it to the service) and then add it as the response body and send to the user.
It would be ideal if you could somehow configure the ObjectMapper, which is used by Spring behind the scenes to do this, however, this is not possible ( at least easily ), because you need to tie this objectMapper to your specific controller only and not all controllers.

Different #JsonProperty config for READ and WRITE on same field?

I have a class (which cannot be modified) like
public class Standing {
private Integer positionNumber;
private String positionText;
private BigDecimal points;
..
}
When deserializing I get data like:
{
"position": "1",
"points": 10
}
As I cannot modify the Standing class I have a mix-in like:
#JsonDeserialize(converter = StandingSanitizer.class)
public abstract class StandingMixIn {
#JsonProperty(access = JsonProperty.Access.READ_ONLY)
Integer positionNumber;
#JsonProperty(value = "position", access = JsonProperty.Access.WRITE_ONLY)
String positionText;
}
As the received json does not have positionNumber and positionText fields I use the #JsonPropery annotations.
With Access.READ_ONLY I simply ignore the positionNumber field.
And with #JsonProperty(value = "position", access = JsonProperty.Access.WRITE_ONLY) on the positionText field I make sure it's populated with the position field from the json during deserialization.
This works well during deserialization.
Note the StandingSanitizer sets the positionNumber. This as the received position value can be non-number values like DSQ in which case the positionNumber field will be null.
But when serializing I want to output all 3 fields from the Standing class like:
{
"positionText": "1",
"positionNumber": 1,
"points": 10
}
But because of #JsonProperty(value = "position", access = JsonProperty.Access.WRITE_ONLY) on the positionText field it is not serialized unfortunately.
In theory I would like to do have something like:
#JsonDeserialize(converter = StandingSanitizer.class)
public abstract class StandingMixIn {
#JsonProperty(access = JsonProperty.Access.READ_ONLY)
Integer positionNumber;
#JsonProperty(access = JsonProperty.Access.READ_ONLY)
#JsonProperty(value = "position", access = JsonProperty.Access.WRITE_ONLY)
String positionText;
}
where I could use different #JsonProperty annotation for both READ and WRITE.
But this is not possible as duplicate #JsonProperty annotations on a field are not allowed; and as far as I could see there is no support for repeatable annotations.
Is there any other solution to solve this?
One thing I can think of is to have 2 ObjectMapper instances, with 2 different StandingMixIns; 1 for deserializing and 1 for serializing. But I would prefer to keep having 1 ObjectMapper instance, so using 2 would be a last resort.

Thanks #Franjavi, you are indeed right I should use annotations on the getters/setters and not on the field only. I was to focussed on only using the fields as my mix-in classes are written in Groovy with implicit getters/setters.
I slimmed down the class a bit more to just:
public abstract class StandingMixIn {
#JsonProperty(access = JsonProperty.Access.READ_ONLY)
Integer positionNumber;
#JsonProperty(value = "positionText")
public abstract String getPositionText();
#JsonProperty(value = "position")
public abstract void setPositionText(String positionText);
}
(removing the positionText completely and using abstract methods)

You could use the getters and setters to get that extra customization. The get will act as READ and the set as WRITE. Note that you don't need the access properties or the field level annotation:
public abstract class StandingMixIn {
#JsonProperty(access = JsonProperty.Access.READ_ONLY)
Integer positionNumber;
// No annotation on the field
String positionText;
#JsonProperty(value = "positionText")
public String getPositionText() {
return positionText;
}
#JsonProperty(value = "position")
public void setPositionText(String positionText) {
this.positionText = positionText;
}
}

How to map a DTO to multiple entities?

I'm writing a Spring Application, which has two entities that are related by a one to many relationship, lets call them mother and kid.
When I create a mother entity via POST request, I want a kid entity be created automatically. Using the #OneToMany and #ManyToOne annotations, that works fine. At least, as long as I provide the kid information within the MotherService.
Here is my code
Mother.java
#Entity
#Table(name="mother")
public class Mother{
#Id
#Column(name="id", updatable = false, nullable = false)
private Long id;
#Column(name="name")
private String name;
#OneToMany(mappedBy = "mother", cascade = CascadeType.ALL, orphanRemoval = true)
private List<Kid> kidList = new ArrayList<>();
//constructor, getter, setter
private void addKid(Kid kid) {
this.kidList.add(kid);
kid.setMother(this);
}
}
Kid.java
#Entity
#Table(name="kid")
public class Kid{
#Id
#Column(name="id", updatable = false, nullable = false)
private Long id;
#Column(name="name")
private String name;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "mother_id", nullable=false)
private Mother mother;
//constructor, getter, setter
}
MotherController.java
#RestController
#RequestMapping("mothers")
public class MotherController {
#Autowired
private MotherService motherService;
MotherController(MotherService motherService) {
this.motherService = motherService;
}
#PostMapping
Mother createMother(#RequestBody Mother mother) {
return this.motherService.createMother(mother);
}
}
MotherService.java
#Service
public class MotherService {
private MotherRepository motherRepository;
#Autowired
public MotherService (MotherRepository motherRepository) {
super();
this.motherRepository= motherRepository;
}
public Mother createMother(Mother mother) {
Kid kid = new Kid("Peter");
mother.addKid(kid);
return this.motherRepository.save(mother);
}
}
The repositories for mother and kid extend the JpaRepository without any custom methods so far.
My POST request is something like (using Postman)
{
"name":"motherName"
}
Now a mother is created with a name "motherName" and a kid with the name of "Peter".
My idea: Using a DTO
I now try to implement a DTO, that contains the mothers name and the kids name, map this information in the MotherService to the entities and save them via the corresponding repository, so I can define both names in the POST request.
motherDto.java
public class mother {
private String motherName;
private String kidName;
//getter, setter
}
So when I POST
{
"motherName":"Susanne",
"kidName":"Peter"
}
or even better
{
"mother": {
"name":"Susanne"
},
"kid": {
"name":"Peter"
}
}
a mother with name Susanne and a kid with name Peter are created.
My question is
How do I map a DTO to two entities?
Or do I not get something right? Is there an easier way to achieve my goal?

I know this is old and probably long solved, but let me offer a different take on the subject.
Another option would be to design a DTO solely for the purpose of creating the two entities you mentioned. You could call this MotherChildCreationDTO or something like that so the name already conveys its use and maybe create a REST-target consuming the DTO.
Asymmetric DTOs (receiving and sending) are an established pattern, and the DTOs are closely coupled to the REST controller any way.

First solution:
You can don't use DTO and send your JSON with same structure of Mother and kids and Jackson in Spring MVC deserialize it correctly for you.
{
id:2,
name:'sarah'
kidList:[{id:546,name:'bob'},{id:478,name:'tom'}]
}
Second solution:
If you want to different structure in JSON and Models and you can use Jackson annotation like #JsonProperty or #JsonDeserialize. Read this like for more information.
Third solution:
You can use DozzerMapper for complex mapping between your DTO and your Model. you define XML's file for mapping each model to your DTO and DozzerMapper map your DTO to your models.Read this link for more information.

You have 2 ways:
Map DTO to entities by yourself. In this case, you should create custom mapper and define how exactly DTO should be converted to entity. Then just inject and use your custom mapper in service.
Use one of existing mapper libraries. For example, good candidates are MapStruct and ModelMapper. You can find usage examples in corresponding getting started guides.

API Rest with Spring Boot

I'm seeing some videos about API Rest with Spring Boot and so far I've done some basics and when I tried to increase the complexity I'm getting caught.
My idea is in the Post / class, create a new class with students getting the following json:
{
"nome": "Primeira Serie - A".
"alunos": [
"João",
"José",
"Maria"
]
}
And return:
{
"id_classe": 101
}
It happens that it saves the class, but it does not save the students and I have no idea how to show only the id of the class.
I have created the following classes in Java:
Model
Classe.java
package com.example.classe.model;
//Import's suppressed
#Entity
#Table(name = "classe")
public class Classe {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private String nome;
#OneToMany(mappedBy = "classe")
private Set<Aluno> alunos = new HashSet<Aluno>();
//Get's e Set's suppressed
}
Aluno.java
package com.example.classe.model;
//Import's suppressed
#Entity
#Table(name = "aluno")
public class Aluno {
private static int tempID = 0;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private String nome;
#ManyToOne
#JoinColumn(name = "id_classe")
#JsonBackReference
private Classe classe;
public Aluno(String nome) {
tempID++;
this.id = tempID;
this.nome = nome;
}
public Aluno() {
}
//Get's e Set's suppressed
}
Repository
ClasseRepository.java
package com.example.classe.repository;
//Import's suppressed
#Repository
public interface ClasseRepository extends JpaRepository<Classe, Integer> {
public List<Classe> findAll();
}
Controller
ClasseController.java
package com.example.classe.controller;
//Import's suppressed
#RestController
#RequestMapping("/classe")
public class ClasseController {
#Autowired
private ClasseRepository classeRepo;
#RequestMapping(method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public ResponseEntity<Collection<Classe>> getClasse() {
return new ResponseEntity<>(classeRepo.findAll(), HttpStatus.OK);
}
#RequestMapping(method = RequestMethod.POST)
public ResponseEntity<?> salvarClasse(#RequestBody Classe classe) {
return new ResponseEntity<>(classeRepo.saveAndFlush(classe), HttpStatus.CREATED);
}
}
Am I doing everything wrong or did I not understand the concept? But I wanted to understand how to do it that way.
Thanks in advance.
Cesar Sturion

What you want to achieve is totally doable, but requires several changes.
I split my answer into 2 parts:
Save the students
There are several problems with saving:
On POST your incoming json deserialized into objects in which Classe has a reference to Anuli, but Anuli doesn't have a reference toClasse. To check it you can add a break point at the line: return new ResponseEntity<>(... , run in debug mode and check fields of Anuli in Classe. To fix it you can add #JsonManagedReference on aluni field in Classe. Related question
Hibernate can't save referenced objects by default. You have to save them one by one after saving your Classe object or just turn on Cascade persisting. Related question
So, to fix 1 and 2 Classe should have:
#OneToMany(mappedBy = "classe", cascade = CascadeType.PERSIST)
#JsonManagedReference
private Set<Aluno> alunos = new HashSet<Aluno>();
You have to remove custom id generation in Alumi (I am talking about static int tempID). Annotation #GeneratedValue will perfectly generate id for you as soon as you persist an object. This custom generation breaks Hibernate support. I even not talking about that it also breaks the app after restart, not threadsafe etc.
Return id only
On POST returned json represent what was returned in classeRepo.saveAndFlush(classe) so it's an object of Classe.
If you want to return exactly this:
{
"id_classe": 101
}
Then create new class like this:
public class ClasseIdVO {
#JsonProperty("id_casse")
private Integer id;
// Constructors, getter, setter
VO - means View Object, so this object only for representation, not for persisting, etc.
You can use field name id_casse, but it's against Java code convention, so better add #JsonProperty.
Also change your saving code to new ClasseIdVO(classeRepo.saveAndFlush(classe).getId())
Or you can just return id as a number: classeRepo.saveAndFlush(classe).getId()

Not-null property references a transient value - transient instance must be saved before current operation

I have 2 domain models and one Spring REST Controller like below:
#Entity
public class Customer{
#Id
private Long id;
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name="COUNTRY_ID", nullable=false)
private Country country;
// other stuff with getters/setters
}
#Entity
public class Country{
#Id
#Column(name="COUNTRY_ID")
private Integer id;
// other stuff with getters/setters
}
Spring REST Controller:
#Controller
#RequestMapping("/shop/services/customers")
public class CustomerRESTController {
/**
* Create new customer
*/
#RequestMapping( method=RequestMethod.POST)
#ResponseStatus(HttpStatus.CREATED)
#ResponseBody
public com.salesmanager.web.entity.customer.Customer createCustomer(#Valid #RequestBody Customer customer, Model model, HttpServletRequest request, HttpServletResponse response) throws Exception {
customerService.saveOrUpdate(customer);
return customer;
}
// other stuff
}
I am trying to call above REST service with below JSON as body:
{
"firstname": "Tapas",
"lastname": "Jena",
"city": "Hyderabad",
"country": "1"
}
Where country code 1 is already there in Country table. The problem is when I am calling this service getting below error:
org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientPropertyValueException: Not-null property references a transient value - transient instance must be saved before current operation: com.test.model.Customer.country -> com.test.model.Country; nested exception is java.lang.IllegalStateException: org.hibernate.TransientPropertyValueException: Not-null property references a transient value - transient instance must be saved before current operation: com.test.model.Customer.country -> com.test.model.Country
Any help will be appreciated!

Try putting CascadeType.ALL
#OneToOne(fetch = FetchType.EAGER,cascade=CascadeType.ALL)
#JoinColumn(name="COUNTRY_ID", nullable=false)
private Country country;

I had a similar problem. Two entities: Document and Status.
Document had a relationship OneToMany with Status, that represented the history of Status the Document had.
So, there was a #NotNull #ManyToOne reference of Document inside Status.
Also, I needed to know the actual Status of Document. So, I needed another relationship, this time #OneToOne, also #NotNull, inside Document.
The problem was: how can I persist both entities the first time if both had a #NotNull reference to the other?
The solution was: remove #NotNull reference from actualStatus reference. This way, it was able to persist both entities.

Just to add an additional scenario that led me to this exact same error:
Make sure that any backward references that may exist are not null.
Specifically in my case, I was using Mapstruct to update some fields of the entity, e.g.
MyClass newInstance = //...
MyClass dbInstance = repository.findByField(someField);
MyClassMapper.MAPPER.update(dbInstance, newInstance);
repository.save(dbInstance);
And my poor implementation of MyClassMapper led the backward references of dbInstance fields to be set to null when they should be pointing back to dbInstance.

I got same error and this is how I solved it:
1st Entity:
#Entity
public class Person implements Serializable{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int personId;
private String name;
private String email;
private long phoneNumber;
private String password;
private String userType;
#OneToOne(fetch = FetchType.LAZY, mappedBy = "personCustomer", cascade
= CascadeType.ALL)
private Customer customer;
2nd Entity:
#Entity
public class Customer implements Serializable{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int customerId;
#OneToOne(fetch = FetchType.LAZY, optional = false, cascade =
CascadeType.ALL)
#JoinColumn(name = "person_customer")
#JsonIgnore
private Person personCustomer;
My Controller:
#PostMapping("/customer/registration")
public PersonCustomer addCustomer(#RequestBody Person person)
{
Customer customer = new Customer(person);
person.setCustomer(customer);
Customer cust = customerRepo.save(customer);
logger.info("{}", cust);
Optional<Person> person_Cust =
personRepo.findById(cust.getPersonCustomer().getPersonId());
Person personNew = person_Cust.get();
PersonCustomer personCust = new PersonCustomer();
if(cust.equals(null))
{
personCust.setStatus("FAIL");
personCust.setMessage("Registration failed");
personCust.setTimestamp(personCust.timeStamp());
}
personCust.setStatus("OK");
personCust.setMessage("Registration OK");
personCust.setTimestamp(personCust.timeStamp());
personCust.setPerson(personNew);
return personCust;
}
The problem got solved when I added "person.setCustomer(customer);".
As both POJO classes has each others reference, so we have to "set" each others reference before using the JPA repository method(customerRepo.save(customer));

I had the exact same problem. The solution seems to be to send the JSON like this:
{
"firstname": "Tapas",
"lastname": "Jena",
"city": "Hyderabad",
"country": {"id":"1"}
}
I guess #RequestBody tries to map an entity not a single field since the Customer instance is referencing a Country instance.
(I have similarly two entities, joined. In the DB, records for the referenced entity (Country in your case) were already created but the entity creation (Customer in your case) with a json, provided the same error message. For me CascadeType.ALL not helped but the above written change in the JSON solved the problem. For further config of course CascadeType can be considered.)

you should change :
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name="COUNTRY_ID", nullable=false)
private Country country;
to :
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name="COUNTRY_ID")
private Country country;
just delete nullable setting.