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How to solve the targeting an unmapped class error from hibernate?

I'm trying to map 2 entities (Course and Student), I have 2 Java classes and 2 MySQL tables, having a ManyToMany relationship. I created the junction table and java class Enrolment (as I want extra information such as the date of enrolment of a student to a course).
I'm trying to insert data using hibernate in this Enrolments table in the MySQL but I keep getting errors. Here are my POJO classes:
Course class:
#Entity
#Table(name = "course")
public class Course {
private int id;
#Column(name = "chapter_id")
private int chapterId;;
#Column(name = "name")
private String title;
#Column(name = "teacher_user_id")
private int teacherId;
#OneToMany(targetEntity=Enrolment.class, mappedBy="course", fetch=FetchType.LAZY)
// #JoinTable(name = "enrolment",
// joinColumns = #JoinColumn(name = "course_id"),
// inverseJoinColumns = #JoinColumn(name = "student_user_id"))
private List<Enrolment> enrolments = new ArrayList<Enrolment>();
public Course(){}
public Course(int id, int chapterId, String title, int teacherId) {
super();
this.id = id;
this.chapterId = chapterId;
this.title = title;
this.teacherId = teacherId;
}
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getChapterId() {
return chapterId;
}
public void setChapterId(int chapterId) {
this.chapterId = chapterId;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public int getTeacherId() {
return teacherId;
}
public void setTeacherId(int teacherId) {
this.teacherId = teacherId;
}
#OneToMany(mappedBy = "course")
public List<Enrolment> getEnrolments() {
return enrolments;
}
public void setEnrolments(List<Enrolment> courses) {
this.enrolments = courses;
}
public void addEnrolment(Enrolment enrolment) {
this.enrolments.add(enrolment);
}
}
Student class (this class is inherited from User parent class, I will attach User Class down below as well. In the database there are different tables as well: User and then Student and Teacher that inherit User parent entity):
#Entity
#Table(name = "student")
#PrimaryKeyJoinColumn(name = "user_id")
#OnDelete(action = OnDeleteAction.CASCADE)
public class Student extends User {
private int grade;
private List<Enrolment> enrolments = new ArrayList<Enrolment>();
public Student(){}
public Student(String fname, String lname, String email, String password, String address, String phone,
int userType, int grade, boolean isAdmin)
{
super(fname, lname, email, password, address, phone, userType, isAdmin);
this.grade=grade;
}
public int getGrade() {
return grade;
}
public void setGrade(int grade) {
this.grade = grade;
}
public void setEnrolments(List<Enrolment> courses) {
this.enrolments = courses;
}
#OneToMany(mappedBy = "student")
public List<Enrolment> getEnrolments() {
return enrolments;
}
public void addCourse(Enrolment course) {
this.enrolments.add(course);
}
public void addEnrolment(Enrolment enrolment) {
this.enrolments.add(enrolment);
}
}
User Class:
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
#Table(name = "user")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String firstname;
private String lastname;
private String email;
private String password;
private String address;
private String phone;
#Column(name = "user_type_id")
private int userType;
#Column(name = "is_admin")
private boolean isAdmin;
public User(String fname, String lname, String email, String password, String address, String phone,
int userType, boolean isAdmin) {
//super();
this.firstname = fname;
this.lastname = lname;
this.email = email;
this.password = password;
this.address = address;
this.phone = phone;
this.userType = userType;
this.isAdmin = isAdmin;
}
public User() {}
//getters & setters
And finally this is the Enrolment class:
#Entity
#Table(name = "enrolment")
public class Enrolment {
private int id;
private Student user;
private Course course;
#Column(name = "enrolment_date")
private Date enrolmentDate;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
#ManyToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "student_user_id")
public User getUser() {
return user;
}
public void setUser(Student user) {
this.user = user;
}
#ManyToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "course_id")
public Course getCourse() {
return course;
}
public void setCourse(Course course) {
this.course = course;
}
public Date getEnrolmentDate() {
return enrolmentDate;
}
public void setEnrolmentDate(Date enrolmentDate) {
this.enrolmentDate = enrolmentDate;
}
So I'm trying to read a course and a student from database and insert the information in this Enrolment table but it gives errors since trying to read a Course. Here is the DAO method:
#SuppressWarnings("deprecation")
#Transactional
public List<Course> getCoursesOfChapter(int chapterId) {
Configuration con = new Configuration().configure("hibernate.cfg.xml").addAnnotatedClass(Course.class);
SessionFactory sf = con.buildSessionFactory();
Session session = sf.openSession();
Transaction tx = session.beginTransaction();
Query query = session.createQuery("from Course where chapter_id = :chapterId");
query.setParameter("chapterId",chapterId);
// List list = query.list();
tx.commit();
return (List<Course>) query.list();
It throws the error at the session factory building:
Exception in thread "main" org.hibernate.AnnotationException: Use of #OneToMany or #ManyToMany targeting an unmapped class: models.Course.enrolments[models.Enrolment]
at org.hibernate.cfg.annotations.CollectionBinder.bindManyToManySecondPass(CollectionBinder.java:1255)
at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:808)
at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:733)
at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:54)
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1696)
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1664)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:287)
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:84)
at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:474)
at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:85)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:689)
at dao.CourseDAO.getCourse(CourseDAO.java:52)
at webapp.Main.main(Main.java:132)
Finally, this is my call:
CourseDAO cdao = new CourseDAO();
Course course = cdao.getCourse(1);
I've tried playing with the annotations, make them ManyToMany instead of ManyToOne. I tried to map the User class instead of Student but still didn't work. I tried to make it without the junction class of Enrolment and just generate it without having an actual class for it but still didn't work (as I had to work with 2 session.save() methods one after the other which also gave some error that I couldn't solve). Probably it's a small thing that I'm missing here but I just can't figure it out, sorry for too long code but I really need to solve it fast. If you read through here, I really thank you!
So my question is: Am I missing something here from these mappings and annotations or I should change the structure of my classes?

Boiling down a problem to the bare minimum greatly helps others help you. Here are simpler versions of your student, course and enrollment classes that can be unit tested easily. The many-to-many association between course and student is separated into two many-to-one associations from Enrollment. Note that the associations are bidirectional and that the many side is mapped by the one side. Student cascades persistence operations to Enrollment, which reflects how schools normally work: students enroll in courses, not the other way around.
Course.java
#Entity
public class Course {
#Id
#GeneratedValue
private Long id;
private String title;
#OneToMany(mappedBy = "course")
private List<Enrollment> enrollments;
Course() {
}
Course(String title) {
this.title = title;
this.enrollments = new ArrayList<>();
}
void add(Enrollment enrollment) {
enrollments.add(enrollment);
}
Long getId() {
return id;
}
List<Enrollment> getEnrollments() {
return enrollments;
}
}
Student.java
#Entity
public class Student {
#Id
#GeneratedValue
private Long id;
private String name;
#OneToMany(mappedBy = "student", cascade = ALL, orphanRemoval = true)
private List<Enrollment> enrollments;
Student() {
}
Student(String name) {
this.name = name;
this.enrollments = new ArrayList<>();
}
void enroll(Course course) {
enrollments.add(new Enrollment(course, this));
}
}
Enrollment.java
#Entity
public class Enrollment {
#Id
#GeneratedValue
private Long id;
#ManyToOne
private Course course;
#ManyToOne
private Student student;
Enrollment() {
}
Enrollment(Course course, Student student) {
this.course = course;
this.student = student;
course.add(this);
}
}
The test case below checks that the entities are mapped and associated correctly. You can run it with Spring Boot.
SchoolTest.java
#RunWith(SpringRunner.class)
#SpringBootTest
#Transactional
public class SchoolTest {
#Autowired
private CourseRepository courseRepository;
#Autowired
private StudentRepository studentRepository;
#Test
public void run() {
Course course = courseRepository.save(new Course("cs_101"));
int studentCount = 3;
for (int i = 1; i <= studentCount; i++) {
Student student = new Student("student_" + i);
student.enroll(course);
studentRepository.save(student);
}
// push changes to the database and clear the existing entities
// to make the subsequent operations load from the database
entityManager.flush();
entityManager.clear();
Optional<Course> savedCourse = courseRepository.findById(course.getId());
assertTrue(savedCourse.isPresent());
assertEquals(studentCount, savedCourse.get().getEnrollments().size());
}
}

As the warning said, your Enrollment is not registered in Hibernate. If you really don't need it. Please use transient annotation. read more here

Foreign key constraint is not created in one-to-one relationship in jpa

I have one-to-one relationship with the following configuration:
#Entity
#Table(name = "org")
#SequenceGenerator(name = "default_gen", sequenceName = "haj_rasoul", allocationSize = 1)
public class Organization extends BaseEntity<Long> {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
and this class:
#Entity
#Table(name = "product")
#GenericGenerator(name = "default_gen", strategy = "foreign", parameters = #Parameter(name = "property", value = "reza"))
public class Product extends BaseEntity<Long> {
#Column(name = "DD")
private String description;
#Column(name = "PP")
private BigDecimal price;
#Column(name = "MM")
private String imageUrl;
#OneToOne
#PrimaryKeyJoinColumn(referencedColumnName = "id")
private Organization reza;
public Organization getReza() {
return reza;
}
public void setReza(Organization reza) {
this.reza = reza;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
public String getImageUrl() {
return imageUrl;
}
public void setImageUrl(String imageUrl) {
this.imageUrl = imageUrl;
}
}
and the BaseEntity:
#MappedSuperclass
public abstract class BaseEntity<T> implements Serializable {
private static final long serialVersionUID = 4295229462159851306L;
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "default_gen")
private T id;
#Column(name = "updatedby")
private Date updatedDate;
public Date getUpdatedDate() {
return updatedDate;
}
public void setUpdatedDate(Date updatedDate) {
this.updatedDate = updatedDate;
}
public T getId() {
return id;
}
public void setId(T id) {
this.id = id;
}
}
When the application is started with the update mode for creation the models,
they are created successfully but foreign key Organization does not exist in the Product, another hand the record of Organization can be deleted in the event that it is in the Product as foreign key.
Where is wrong?
How do i fix this problem?

Update fk with hibernate

My picture table with two OneToOne relations to the User table:
Picture entity:
#Entity
#Table(name = "pictures")
public class Picture implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
public int getId() {
return id;
}
#OneToOne
#JoinColumn(name = "customer_id", nullable = true)
private User customer;
public User getCustomer() {
return customer;
}
public void setCustomer(User customer) {
this.customer = customer;
}
#OneToOne
#JoinColumn(name = "photographer_id", nullable = false)
private User photographer;
public User getPhotographer() {
return photographer;
}
public void setPhotographer(User photographer) {
this.photographer = photographer;
}
private String title;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
private String url;
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
private BigDecimal price;
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
public Picture(String title,
String url,
BigDecimal price)
{
this.title = title;
this.url = url;
this.price = price;
}
public Picture() {
// Empty constructor
}
}
PictureDaoImpl:
#Override
public void insert(Picture object) {
sessionFactory.getCurrentSession().save(object);
}
How can I update the two foreign keys customer_id and photographer_id?
In the entity the two foreign keys are OneToOne relations to User
The error I get is Column 'photographer_id' cannot be null

You made an extremely wrong DB design.
Between DB entities you can't make two relations, between tables\entities
can be only and only single relation.
According to your design you need to relation of #OneToMany relation between Picture and User, for every single/one picture you have many users, even if da facto you'll eventually have only two users, because two are still not one/single, so it's being considered as Many.
I suggest that first do your redesign DB.

Retrieve data using hsql - relation many to one

I define the following entities :BaseEntity , magasin and article :
#Entity(name = "magasin")
#Table(name = "magasin")
public class Magasin extends BaseEntity {
private static final long serialVersionUID = 1L;
#Basic
#Size(min=5, max=100, message="The name must be between {min} and {max} characters")
private String name;
#OneToMany(cascade=CascadeType.ALL, mappedBy="magasin")
#Valid
private Set<Article> article;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Article> getArticle() {
return article;
}
public void setArticle(Set<Article> article) {
this.article = article;
}
}
#Entity(name="article")
#Table(name="article")
public class Article extends BaseEntity {
private static final long serialVersionUID = 1L;
#ManyToOne
private Magasin magasin;
#Basic
#Size(min=5, max=100, message="The name must be between {min} and {max} characters")
private String name;
#Basic
private float price;
public Magasin getMagasin() {
return magasin;
}
public void setMagasin(Magasin magasin) {
this.magasin = magasin;
}
public String getName() {
return name;
}
public void setName(String nom) {
this.name = nom;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
}
#MappedSuperclass
public class BaseEntity {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Integer id;
public void setId(Integer id) {
this.id = id;
}
public Integer getId() {
return id;
}
public boolean isNew() {
return (this.id == null);
}
}
How can create a hql query in order to retrieve all Article for a magasin selected ?
I try this
#Override
public List<Article> findArticle(Magasin magasin) {
String query = "From Article m where m.magasin.id = "+magasin.getId();
System.out.print(query);
Session session = getSessionFactory().getCurrentSession();
if((session.createQuery(query).list()!=null) && (session.createQuery(query).list().size()!=0))
return (List<Article>) session.createQuery(query).list();
else
return null;
}
But it returns nothing , always null .How can I resolve it ?

I don't know the type of your magasin id so adapt the code below.
First get the Magasin instance for the id:
Magasin mag = (Magasin)session.get(Magasin.class, id);
Next you can access the articles for the magasin mag via accessor
Set<Article> articles = mag.getArticle();

Try this:
"Select * From Article,Mgasin where Article.mgasin.id = "+magasin.getId();

Hibernate annotations one-to-one

I need help to create mapping Hibernate Annotations (ONE-to-ONE) in java classes for these relation tables:
CREATE TABLE book
(
id_book integer NOT NULL,
isdn character varying(10) NOT NULL,
CONSTRAINT "pk_bookId" PRIMARY KEY ("id_book")
)
CREATE TABLE info
(
id_info serial NOT NULL,
title character varying(200),
author character varying(200),
id_book integer NOT NULL,
CONSTRAINT info_pkey PRIMARY KEY ("id_info"),
CONSTRAINT "info_id_book_fkey" FOREIGN KEY ("id_book")
REFERENCES book ("id_book") MATCH SIMPLE
ON UPDATE CASCADE ON DELETE NO ACTION,
CONSTRAINT "info_id_book_key" UNIQUE ("id_book")
)
Can anyone help me? Thank you.

You can create one to one relation ship between these two entities like below.
#Entity
#Table(name = "book")
class book{
private int id;
private String isdn;
private Info info;
#Id
#Column(name="id_book", unique=true, nullable=false)
#GeneratedValue
public int getId(){
return this.id;
}
#Column(name="isdn")
public String getIsdn(){
return this.idsn;
}
public void setId(int id){
this.id = id;
}
public void setIsdn(String isdn){
this.isdn = isdn;
}
#OneToOne
#PrimaryKeyJoinColumn
public Info getInfo(){
return this.info;
}
public void setInfo(Info info){
this.info = info;
}
}
#Entity
#Table(name = "info")
class Info{
private int id;
private String title;
private String author;
private Book book;
#Id
#Column(name="id_info", unique=true, nullable=false)
#GeneratedValue
public int getId(){
return this.id;
}
#Column(name="title")
public String getTitle(){
return this.title;
}
public void setId(int id){
this.id = id;
}
public void setTitle(String title){
this.title = title;
}
#OneToOne(mappedBy="info", cascade=CascadeType.ALL)
public Book getBook(){
return this.book;
}
public void setBook(Book book){
this.book = book;
}
public void setAuthor(String author){
this.author = author;
}
#Column(name="author")
public String getAuthor(){
return this.author ;
}
}