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Spring boot JPA: How to keep the child entity when deleting the parent entity in a many-to-one relationship?

I'm new to the Spring boot JPA and struggling to find out the relationships between multiple entities.
I have a User Entity, a Product Entity, and a Review Entity.
A user has many reviews.
A product has many reviews.
A review has a product and a user.
At the moment, I'm using one-to-many relationships for user&reivew, product&review. However, the error occurred when deleting a review: ERROR: update or delete on table "users" violates foreign key constraint "fkcgy7qjc1r99dp117y9en6lxye" on table "reviews".
My question:
How can I delete a Review Entity without deleting the Product entity and User entity?
Which cascade type should I use?
User Entity:
#Entity
#Table(name = "users")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "user_name")
private String userName;
#Column(name = "email")
private String email;
#Column(name = "password")
private String password;
#JsonManagedReference("reviews")
#JsonIgnore
#OneToMany(fetch = FetchType.LAZY,
mappedBy = "user")
private List<Review> reviews = new ArrayList<>();
//constructor + getter+ setter
Product Entity:
#Entity
#Table(name = "products")
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private Float price;
#Transient
private Float rate;
private String category;
private String brand;
#JsonManagedReference("reviews")
#JsonIgnore
#OneToMany(mappedBy = "product")
List<Review> reviews = new ArrayList<>();
//constructor + getter+ setter
Review Entity:
#Entity
#Table(name = "reviews")
public class Review {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private Float rate;
private String comment;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "user_id",referencedColumnName = "id")
#JsonBackReference("user")
private User user;
#ManyToOne(fetch = FetchType.LAZY)
#JsonBackReference("product")
#JoinColumn(name = "product_id",referencedColumnName = "id")
private Product product;
//constructor + getter+ setter
User Controller:
#CrossOrigin(origins = "http://localhost:3000")
#RestController
#RequestMapping(path="users/")
public class UserController {
private final UserService userService;
#Autowired
public UserController(UserService userService) {
this.userService = userService;
}
...
#DeleteMapping("{userid}")
public User deleteUser(#PathVariable("userid") Long userid){
return userService.deleteById(userid);
}
}
User service:
#Service
public class UserService {
private final UserRepository userRepository;
private final ReviewRepository reviewRepository;
//dependency injection
#Autowired
public UserService(UserRepository userRepository, ReviewRepository reviewRepository) {
this.userRepository = userRepository;
this.reviewRepository =reviewRepository;
}
...
public User getUserById(Long id){
return userRepository.findById(id).orElseThrow(()->
new UserNotFoundException(id));
}
public User deleteById(Long id){
User user = getUserById(id);
userRepository.delete(user);
return user;
}
}
Simple run:
#SpringBootApplication
public class GroceryShoppingAppApplication {
public static void main(String[] args) {
ConfigurableApplicationContext configurableApplicationContext =
SpringApplication.run(GroceryShoppingAppApplication.class, args);
UserRepository userRepository = configurableApplicationContext.getBean(UserRepository.class);
ProductRepository productRepository =configurableApplicationContext.getBean(ProductRepository.class);
ReviewRepository reviewRepository = configurableApplicationContext.getBean(ReviewRepository.class);
User debbi= new User("Debbi","debbi#gamil.com","password");
Product apple = new Product("Apple",(float)3.40,"Fruit","Gala");
Product milk = new Product("Milk",(float)5.22,"Dairy","Anchor");
Review review1 = new Review(debbi,(float)4.5,"Good taste",apple);
Review review2 = new Review(debbi,(float)5.0,"Good milk",milk);
productRepository.save(apple);
productRepository.save(milk);
userRepository.save(debbi);
reviewRepository.save(review1);
reviewRepository.save(review2);
I think I should not use casacadeType.All because when deleting a user, I shouldn't delete the product in the review. I tried other types, the error still remains. Thus, currently I didn't use any casacadeType and need to save each entity one by one.
Please help me with this.

You are getting an error because the user in the review model does not have a referenced Column value.
Try this code:
#JoinColumn(name = "user_id",referencedColumnName = "id")

#OneToOne mapping isnt working in my Java Spring project

So I am tidying up my small Spring project and I noticed for some reason the #OneToOne annotation is not doing its job for me which in turn causes issues in another model.
github link : https://github.com/eamonmckelvey/sports-app
Basically, I have a User model class, a team model class and a player model class.
I want only one user to be able to create one team, and one team to have many players.
However, I am able to add as many teams to my user as I want which is wrong.
All the answers provided require me to add a no arg constructor and a constructor for my users class, but when I do this I get an error in my registration from class.
Please help.
1. User Model
#Entity
#Data
#NoArgsConstructor(access= AccessLevel.PRIVATE, force=true)
#RequiredArgsConstructor
public class User implements UserDetails {
#OneToOne(cascade = CascadeType.ALL,mappedBy = "user")
private Team team;
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy= GenerationType.AUTO)
private Long id;
private final String username;
private final String password;
//private final String fullname;
#Override
public Collection<? extends GrantedAuthority> getAuthorities() {
return Arrays.asList(new SimpleGrantedAuthority("ROLE_USER"));
}
#Override
public boolean isAccountNonExpired() {
return true;
}
#Override
public boolean isAccountNonLocked() {
return true;
}
#Override
public boolean isCredentialsNonExpired() {
return true;
}
#Override
public boolean isEnabled() {
return true;
}
}
2. Team Model
#Data
#Entity
#Table(name="User_Team")
public class Team implements Serializable {
#OneToOne(fetch= FetchType.LAZY)
private User user;
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy= GenerationType.AUTO)
private Long id;
//#NotBlank(message="Team Name is required")
private String teamName;
//#NotBlank(message="Location is required")
private String location;
//#NotBlank(message="Nickname required")
private String nickName;
private String yearEstablished;
public Sport sport;
private Divison divison;
3. Team Controller
#Slf4j
#Controller
#SessionAttributes("Team")
public class TeamController {
private TeamRepository teamRepository;
public TeamController(TeamRepository teamRepository) {
this.teamRepository = teamRepository;
}
#Autowired
TeamRepository service;
#GetMapping("/team")
public String displayTeam(Model model) {
model.addAttribute("team", service.findAll());
return "/team";
}
#GetMapping("/addTeam")
public String showSignUpForm(User user) {
return "addTeam";
}
#PostMapping("/addTeam")
public String processOrder(#Valid Team team, BindingResult result, SessionStatus
sessionStatus,
#AuthenticationPrincipal User user, Model model) {
if (result.hasErrors()) {
return "addTeam";
}
team.setUser(user);
service.save(team);
model.addAttribute("team", service.findAll());
return "team";
}
4. Registeration Form
#Data
public class RegistrationForm {
private String username;
private String password;
//private String fullname;
public User toUser(PasswordEncoder passwordEncoder) {
return new User(
username, passwordEncoder.encode(password));
}
}
5. Registration Controller
#Controller
#RequestMapping("/register")
public class RegistrationController {
private UserRepository userRepo;
private PasswordEncoder passwordEncoder;
public RegistrationController( UserRepository userRepo,
PasswordEncoder passwordEncoder){
this.userRepo = userRepo;
this.passwordEncoder = passwordEncoder;
}
#GetMapping
public String registerForm(){
return "registration";
}
#PostMapping
public String processRegistration(RegistrationForm form){
userRepo.save(form.toUser(passwordEncoder));
return "redirect:/login";
}
6. user details class
#Service
public class UserRepositoryUserDetailsService implements
UserDetailsService {
private UserRepository userRepo;
#Autowired
public UserRepositoryUserDetailsService(UserRepository userRepo) {
this.userRepo = userRepo;
}
#Override
public UserDetails loadUserByUsername(String username) throws
UsernameNotFoundException {
User user = userRepo.findByUsername(username);
if (user != null) {
return user;
}
throw new UsernameNotFoundException(
"User '" + username + "' not found");
}

1) One user can have one team. That means OneToOne relation between user and team. You need not to annotate both user and team with #OneToOne.Remove #OneToOne annotation from team model.
Changes required are:
User model:
#Entity
class User{
#Id
private String id;
#OneToOne(fetch = FetchType.LAZY,cascade = CascadeType.ALL)
#JoinColumn(name = "team_id")
private Team team;
//other fields
}
Team Model:
#Entity
class Team{
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String teamName;
//other field
}
2) For one team to have many players requires #OneToMany

So, I copied your code and did some changes. After the following changes your code works fine.
1) Drop final keyword from below fields in user class(initalizing them doesn't seems to be a great idea).
private final String username;
private final String password;
2) User and Team should not have same serialization version.
private static final long serialVersionUID = 1L;
3) After doing above corrections. Your code will give you the actual error "nested exception is javax.persistence.PersistenceException"
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)
..............
..........
Caused by: org.postgresql.util.PSQLException: ERROR: syntax error at or near "user"
To avoid it do the following changes in your model :
Put #Table(name="users") in user model.
Following are the models:
#Entity
#Table(name="users")
public class User {
#Id
#GeneratedValue(strategy= GenerationType.AUTO)
private Long id;
private String username;
#OneToOne(mappedBy = "user")
private Team team;
public User() {
}
}
Team Model
#Table(name="teams")
public class Team {
#Id
private Long id;
#OneToOne
#MapsId
// or you can use
// #OneToOne
// #JoinColumn(name="user_id")
private User user;
private String teamName;
public Team() {
}
}
Follow the above code. It works fine for me. Test Controller to check:
#RequestMapping(value = "/test", method = RequestMethod.GET)
public ResponseEntity<?> test() {
User user = userRepository.findById(2l);
Team team = user.getTeam();
return new ResponseEntity(team, HttpStatus.OK);
}
}
I hope this will help you out.

There are several issues with your code:
#JoinColumn on the child side is missing. It's not even on the parent side. In the User entity you declare #OneToOne(cascade = CascadeType.ALL,mappedBy = "user"), but it is not mapped in the child class.
FetchType.LAZY does not give you much in terms of performance in one-to-one, since hibernate needs to check the database for existence of an object to know whether return a proxy or null.
You're saving a child entity in your TeamController: service.save(team);, but there is no cascading from Team to User.
Try the following mapping:
public class User implements UserDetails {
#OneToOne(cascade = CascadeType.ALL, mappedBy = "user")
private Team team;
// other fields
}
public class Team implements Serializable {
#OneToOne(cascade=CascadeType.ALL)
#JoinColumn(name = "user_id")
private User user;
// other fields
}
And keeping both sides synchronized. Instead of:
team.setUser(user);
service.save(team);
Try the following code in your TeamController (you will have to autowire UserRepository):
team = service.save(team);
team.setUser(user);
user.setTeam(team);
userRepository.save(user);

Hey so i found a fix here for my code.
1. Team Controller
#GetMapping("/addTeam")
public String showSignUpForm(SessionStatus sessionStatus,
#AuthenticationPrincipal User user, Model model)
{
//if the user has already the team we should not let them add another
// one
//this is due to having one to one relationship
long userHasTeamCount = service.countAllByUser(user);
if (userHasTeamCount > 0) {
return "redirect:team";
}
return "addTeam";
}
2. Team model
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "user_id", referencedColumnName = "id")
private User user;
3. User Model
Removed the OneToOne here as its not needed
4. Team repo
#Repository
public interface TeamRepository extends JpaRepository<Team, Long> {
Team findAllById(Long id);
long countAllByUser(final User user);
}

Hibernate one-to-many relationship java.sql.SQLIntegrityConstraintViolationException: Column 'person_id' cannot be null

I'm new to hibernate, learn doc save persistent object
followed hibernate doc this is person and phone relationship one-to-many
#Entity
#Table(name = "phone")
public class Phone {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
#Column(name = "number")
private String number;
#ManyToOne(fetch = FetchType.LAZY)
private Person person;
//omit setter and getter
}
#Entity
#Table(name = "person")
public class Person {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
private String username;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "person")
private List<Phone> phones = new ArrayList<>();
//omit getter and setter
}
I'm persistent person and add one phone the error be throw
#Test
public void say() {
Person person = new Person();
person.setUsername("aaaa");
Phone phone = new Phone();
phone.setNumber("111");
person.getPhones().add(phone);
personService.save(person);
}
this is Dao persistent
public class PersonDaoImpl implements PersonDao {
#PersistenceContext
private EntityManager entityManager;
#Override
public void save(Person person) {
entityManager.persist(person);
}
Update service code, service just save person
#Service(value = "personService")
public class PersonServiceImpl implements PersonService {
#Autowired
private PersonDao personDao;
#Transactional
#Override
public void save(Person person) {
personDao.save(person);
}
}
error info:
23:35:47.059 [main] DEBUG org.hibernate.engine.spi.ActionQueue - Executing identity-insert immediately
23:35:47.062 [main] DEBUG org.hibernate.SQL -
insert
into
phone
(number, person_id)
values
(?, ?)
23:35:47.297 [main] DEBUG org.hibernate.engine.jdbc.spi.SqlExceptionHelper - could not execute statement [n/a]
java.sql.SQLIntegrityConstraintViolationException: Column 'person_id' cannot be null

Add the #GeneratedValue annotation to specify that the primary key for both entities will be populated outside of your code.
#Entity
#Table(name = "phone")
public class Phone {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private long id;
#Column(name = "number")
private String number;
#JoinColumn("person_id")
#ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Person person;
//omit setter and getter
}
public class Person {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private long id;
private String username;
#OneToMany(mappedBy = "person")
private List<Phone> phones = new ArrayList<>();
//omit getter and setter
}
Additionally, you need to persist the Person object instead of the Phone object because there is no cascade configured from Phone to Person. If you can't do that, switch the CascadeType on Person to none and put the cascade on the Phone as shown above.
You should also add a #JoinColumn annotation on the Phone entity so hibernate is aware of the foreign key column.

You Missed something. You can try with this.
Person Entity
#Entity
public class Person {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
private String username;
#OneToMany(mappedBy = "person")
private List<Phone> phones = new ArrayList<>();
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public List<Phone> getPhones() {
return phones;
}
public void setPhones(List<Phone> phones) {
this.phones = phones;
}
//omit getter and setter
}
Phone Entity
#Entity
#Table(name = "phone")
public class Phone {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
#Column(name = "number")
private String number;
#ManyToOne(cascade = CascadeType.PERSIST)
private Person person;
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
//ommit setter and getter
}
Phone Dao
public interface PhoneDao {
public Phone save(Phone phone);
}
PhoneDaoImpl
#Repository
public class PhoneDaoImpl implements PhoneDao {
#PersistenceContext
private EntityManager entityManager;
#Override
public Phone save(Phone phone) {
return entityManager.merge(phone);
}
}
PersonDaoImpl
#Repository
public class PersonDaoImpl implements PersonDao{
#PersistenceContext
private EntityManager entityManager;
#Override
public Person save(Person person) {
return entityManager.merge(person);
}
}
Test Method
#Test
#Transactional
#Commit
public void say()
{
Phone phone = new Phone();
phone.setNumber("jghjkhk");
Person person = new Person();
person.setUsername("7576");
phone.setPerson(person);
Phone pers = phoneDao.save(phone);
Assert.assertNotNull(pers);
}
Try now. It will work.

I think that you need to set the value of the person->id and then also use an getter method to pass the id to your phone object instead of passing the person object

Normally people have hibernate set the id of an entity automatically with a surrogate key.
public class Person {
#Id #GeneratedValue // should pick an appropriate strategy here
private long id;
Since you don't have that you must either add it or set it yourself.
Person p = new Person();
p.setId(1); // hopefully unique
The same goes for phone.

As you are not having any generation type on your #Id and id is the primary key which can not be null so either you have to set value of id or have #GeneratedValue annotation on your id field and set strategy either as Auto or Identity.
You can also have your own sequence generation.
Also, you need to do same for the Phone class.

How to persist nested objects with Hibernate?

I have two classes, Customer and ShoppingCart. The java structure of the two classes is the following:
Customer class:
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
public class Customer extends User implements Serializable {
#OneToOne(mappedBy = "owner", cascade=CascadeType.ALL)
private ShoppingCart shoppingCart;
#OneToMany(mappedBy = "customer", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<Purchase> purchases;
public Customer() {
super();
}
public Customer(String username, String email, String password) {
super(username, email, password);
this.shoppingCart = new ShoppingCart();
this.purchases = new ArrayList<>();
}
getters and setters
}
ShoppingCart class:
#Entity
public class ShoppingCart implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer shoppingCartId;
#OneToOne
#JoinColumn(name = "owner_id")
private Customer owner;
#OneToMany(mappedBy = "shoppingCart")
private List<CartItem> items;
public ShoppingCart(Customer owner) {
this.owner = owner;
this.items = new ArrayList<>();
}
public ShoppingCart() {
this.items = new ArrayList<>();
}
getters and setters
}
If needed, this is the User class:
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
public class User implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE)
private Integer userId;
private String username;
private String email;
private String password;
public User() {
}
public User(String username, String email, String password) {
this.username = username;
this.email = email;
this.password = password;
}
getters and setters
}
I have configured the Repositories classes in this way:
#Repository
public interface CustomerRepository extends CrudRepository<Customer, Integer> {
}
#Repository
public interface UserRepository extends CrudRepository<User, Integer> {
}
#Repository
public interface ShoppingCartRepository extends CrudRepository<ShoppingCart, Integer> {
}
What I want is simple, once I create a Customer, I also want to create a ShoppingCart tuple inside the database. And it actually works fine, the only problem is that the foreign key of the ShoppingCart related with the Customer is set to null. I just have the shopping_cart_id attribute set to an integer value (correctly).
The code I used to test it is the following:
Customer customer = new Customer("stefanosambruna", "ste23s#hotmail.it", "*******");
customerRepository.save(customer);
Now, I may have put some annotations in the wrong places, but I really don't know which ones. Is it related to the constructors? Or to the #JoinColumn and mappedBy configurations? I read all the Q&As about this topic here on StackOverflow and on some other sources, but I didn't find anything 100% useful. Hope to have given all the necessary details.

Form Validation in Rest Webservice

I started building my first REST webservice in Java using Spring and JPA.
Now I'm trying to create sign-up service. I have no problem with sending a request containing all Entity fields what looks:
#AllArgsConstructor
#NoArgsConstructor
#Data
#Builder
#Entity
#Table(name = "users")
public class User implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#Enumerated(EnumType.STRING)
private Gender gender;
#Column(name = "email")
private String email;
#Column(name = "login")
private String login;
#Column(name = "password")
private String password;
#Column(name = "registration_date")
#CreatedDate
private LocalDateTime registrationDate;
#OneToMany(mappedBy = "bookOwner", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private List<Book> bookList = new ArrayList<>();
}
But what to do in situation I want my registration form having only login, password and email fields and filling the rest user details would be optional - after confirmation of registration?
I consider using ModelMapper and creating separate classes for every form, but is there any better approach?

I solved problem by my own using mentioned ModelMapper. I paste my code. Can be useful if someone's interested. Didn't make tests, but my DB looks fine and no exceptions are thrown.
public class DTOMapper {
private static final ModelMapper MAPPER = new ModelMapper();
private DTOMapper(){}
public static <S, T> T map(S source, Class<T> targetClass){
return MAPPER.map(source, targetClass);
}
}
#Service
#Transactional
public class SignUpService {
private final UserRepository userRepository;
#Autowired
public SignUpService(UserRepository userRepository) {
this.userRepository = userRepository;
}
public User registerUser(SignUpForm form){
if(userRepository.findByLogin(form.getLogin())!=null){
throw new LoginAlreadyUsedException(form.getLogin());
}
if(userRepository.findByEmail(form.getEmail())!=null){
throw new EmailAlreadyUsedException(form.getEmail());
}
User user = DTOMapper.map(form, User.class);
User saved = userRepository.save(user);
return DTOMapper.map(saved, User.class);
}
}
#AllArgsConstructor
#NoArgsConstructor
#Data
#Builder
public class SignUpForm implements Serializable {
private static final long serialVersionUID = 1L;
#NotEmpty
#Size(min = 5)
private String login;
#NotEmpty
#Size(min = 7)
private String password;
//todo email validation
#NotEmpty
private String email;
}
#RestController
public class SignUpController {
private static final Logger log = LoggerFactory.getLogger(SignUpController.class);
#Autowired
private SignUpService signUpService;
#PostMapping(value = "/signup")
public ResponseEntity<?> addUser(#RequestBody #Valid SignUpForm form, BindingResult errors){
if(errors.hasErrors()){
throw new InvalidRequestException(errors);
}
signUpService.registerUser(form);
return new ResponseEntity<>(form, HttpStatus.CREATED);
}
}