OneToOne Association In JPA not working using Spring boot and spring data JPA

I am trying to implement the OneToOne association in JPA and trying to join two tables using spring boot and spring data JPA. I created one spring boot microservice and implemented the one to one association in my model. But when I am running code I am getting the following error ,

Caused by: org.hibernate.AnnotationException: Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElement


Here My First model class Users.java is like following,

@Entity
@Table(name = "users")
public class Users implements Serializable

private static final long serialVersionUID = 9178661439383356177L;

@Id

@Column(name="user_id")
public Integer userId;

@Column(name="username")
public String username;

@Column(name="password")
public String password;





And I am testing association by controller using following code,

@GetMapping("/load")
public Users load()
return (Users) userObj.findAll();



Can anyone help to resolve this association issue please ?

@OneToMany

Users

@OneToOne

List

@OneToMany

OneToMany

3 Answers
3

This is wrong.

@OneToOne(mappedBy="nuserId")
public Set<UserRoleMapping> roleUserRoleMappingMappingJoin;
}


OneToOne means only one object..right?

See this for mappings understandings.

https://docs.jboss.org/hibernate/orm/3.6/reference/en-US/html/collections.html#collections-persistent

Annotation @OneToOne defines a single-valued association to another entity, and in your case you associate a user to a Set of UserRoleMapping instead of associating it with a single object of that class. Use @ManyToOne annotation

Actually the exception refers to an invalid @OneToMany, @ManyToMany or @CollectionOfElement mapping

@OneToMany, @ManyToMany or @CollectionOfElement

and this can only be

@OneToMany()
@JoinColumn(name="nuser_id" , referencedColumnName="nuserId")
public Users nuserId;


If the @OneToMany relation is valid change this at first to

@OneToMany

@OneToMany()
@JoinColumn(name="nuser_id" , referencedColumnName="nuserId")
public List<Users> users;


If the @OneToMany relation is NOT valid change this to

@OneToMany

@OneToOne()
@JoinColumn(name="nuser_id" , referencedColumnName="nuserId")
public Users users;


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