Java Hibernate Multiple links between two tables

User:

@Entity @Table(name = "users") public class User implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int id; @Column(name = "`name`", nullable = false, unique = true) private String name; @OneToMany(fetch = FetchType.EAGER, mappedBy = "author") private Set<Document> authorDocuments = new HashSet<>(); @OneToMany(fetch = FetchType.EAGER, mappedBy = "concurrent") private Set<Document> concurrentDocuments = new HashSet<>(); public User() { } public User(String name) { this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set<Document> getAuthorDocuments() { return authorDocuments; } public Set<Document> getConcurrentDocuments() { return concurrentDocuments; } public void addDocumentAuthor(Document document) { authorDocuments.add(document); document.setAuthor(this); } public void removeDocumentAuthor(Document document) { authorDocuments.remove(document); document.setAuthor(null); } public void addDocumentConcurrent(Document document) { concurrentDocuments.add(document); document.setConcurrent(this); } public void removeDocumentConcurrent(Document document) { concurrentDocuments.remove(document); document.setConcurrent(null); } } 

Documnet:

 @Entity @Table(name = "documents") public class Document implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int id; @Column(name = "`name`", nullable = false, unique = true) private String name; @ManyToOne(fetch = FetchType.EAGER) @JoinColumn(name = "id_author", nullable = false) private User author; @ManyToOne(fetch = FetchType.EAGER) @JoinColumn(name = "id_concurrent", nullable = false) private User concurrent; public Document() { } public Document(String name) { this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public User getAuthor() { return author; } public void setAuthor(User author) { this.author = author; } public User getConcurrent() { return concurrent; } public void setConcurrent(User concurrent) { this.concurrent = concurrent; } @Override public String toString() { return "Document {" + lineSeparator() + "name: " + name + "," + lineSeparator() + "author: " + author.getName() + "," + lineSeparator() + "concurrent: " + concurrent.getName() + lineSeparator() + "}"; } } 

DocumentRepository:

 @Repository public interface DocumentRepository extends CrudRepository<Document, Integer> { } 

UserRepository:

 @Repository public interface UserRepository extends CrudRepository<User, Integer> { } 

application.properties:

 spring.jpa.hibernate.ddl-auto=validate spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect spring.jpa.show-sql=true spring.datasource.url=jdbc:mysql://localhost:3306/many_to_many?useSSL=false spring.datasource.username=root spring.datasource.password=root spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver 

db.sql:

 drop database if exists many_to_many; create database many_to_many; use many_to_many; create table users ( id int primary key auto_increment, `name` varchar(255) not null unique ); create table documents ( id int primary key auto_increment, `name` varchar(255) not null unique, id_author int not null, id_concurrent int not null, foreign key(id_author) references users(id), foreign key(id_concurrent) references users(id) ); 

Application:

 @SpringBootApplication public class Application implements CommandLineRunner { @Autowired private UserRepository userRepository; @Autowired private DocumentRepository documentRepository; public static void main(String[] args) { SpringApplication.run(Application.class, args); } @Override public void run(String... args) throws Exception { User user1 = new User("user1"); User user2 = new User("user2"); User user3 = new User("user3"); userRepository.save(user1); userRepository.save(user2); userRepository.save(user3); Document document1 = new Document("document1"); Document document2 = new Document("document2"); user1.addDocumentAuthor(document1); user2.addDocumentConcurrent(document1); user1.addDocumentAuthor(document2); user3.addDocumentConcurrent(document2); documentRepository.save(document1); documentRepository.save(document2); documentRepository.findAll().forEach(System.out::println); } } 

Console (Output):

 Document { name: document1, author: user1, concurrent: user2, } Document { name: document2, author: user1, concurrent: user3, }