OneToMany & ManyToOne mapping Spring Boot / Hibernate

Question

I have two tables with foreign key relations. I\'ve tried searching on how to do it and it always leads to OneToMany & ManyToOne mapping. I have these two tables.

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Answer 1

I can re-create your exception by mixing my annotation mapping between fields and properties. I see in the problem you described above you annotate the field Id, but then annotate the property userRole, if I do the same I get the same error. I can fix the error by either annotating just properties or fields. Both these models work:

@Entity
@Table(name = "USER")
public class User {


private Long id;
private UserRole userRole;
String userName;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
    return id;
}


public void setId(Long id) {
    this.id = id;
}

@Column(name = "USER_NAME")
public String getUserName() {
    return userName;
}

public void setUserName(String userName) {
    this.userName = userName;
}

@ManyToOne()
@JoinColumn(name="role_id")
public UserRole getUserRole() {
    return userRole;
}

public void setUserRole(UserRole userRole) {
    this.userRole = userRole;
}
}

This also works:

@Entity
@Table(name = "USER")
public class User {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;


@ManyToOne()
@JoinColumn(name="role_id")
private UserRole userRole;


@Column(name = "USER_NAME")
String userName;

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getUserName() {
    return userName;
}

public void setUserName(String userName) {
    this.userName = userName;
}

public UserRole getUserRole() {
    return userRole;
}

public void setUserRole(UserRole userRole) {
    this.userRole = userRole;
}
}

Example of the other model object annotating the fields

@Entity
@Table(name = "USER")
public class User {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;


@ManyToOne()
@JoinColumn(name="role_id")
private UserRole userRole;


@Column(name = "USER_NAME")
String userName;

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getUserName() {
    return userName;
}

public void setUserName(String userName) {
    this.userName = userName;
}

public UserRole getUserRole() {
    return userRole;
}

public void setUserRole(UserRole userRole) {
    this.userRole = userRole;
}
}

Test Code (I added this because there is often confusion that one must set the bidirectional relationship in order to get both users and userRole to persist with a save to the UserRole).

    List users = new ArrayList<>();

    User user1 = new User();
    user1.setUserName("user1");
    users.add(user1);

    User user2 = new User();
    user2.setUserName("user2");
    users.add(user2);

    UserRole userRole = new UserRole();
    userRole.setRoleName("admin");
    //Unidirectional relationship
    user1.setUserRole(userRole);
    user2.setUserRole(userRole);
    //set Bidirectional relationship
    userRole.setUsers(users);

    userRole = userRoleRepository.save(userRole);

    //Show that the two users and the UserRole persisted
    UserRole result = userRoleRepository.findById(userRole.getId()).get();
    assertEquals(2, result.getUsers().size());