I have an entity class named "User", I want to store a list of data in User.

This is my code :

@Entity
public class User extends BaseEntity {
        
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private String firstName;
    
    private String lastName;
    
    @Column(unique = true)
    private String mail;
    
    private String password;
    
    private List<Feature> features;

}

And i have a Feature Class but its not a entity because it doesn't need to be an entity class, i think.

public class Feature {
    
    private String fName;
    private Long fYear;

}

When I start the application, I get an error:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Could not determine type for: java.util.List, at table: user, for columns: [org.hibernate.mapping.Column(features)]

CodePudding user response：

You can't insert list into SQL table, as a type.

You need to define relation(s):

@Entity
public class User extends BaseEntity {
        
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private String firstName;
    
    private String lastName;
    
    @Column(unique = true)
    private String mail;
    
    private String password;
    
    @OneToMany (or any other relation fitting your case)
    private List<Feature> features;

}

and

@Entity
public class Feature {
   
   @Id
   //define generation strategy here
   private long id;
   
   ​private String fName;
   ​private Long fYear;

}

CodePudding user response：

Since the Feature type does hold instance fields that map to domain data, it should be saved as a separate entity.

If still the Feature is out of your domain boundaries and does not need to be stored along the User, you can mark it as being @Transient and you may need to load its data based on your application semantics when loading a user entity.

Otherwise, you would go a the traditional path of mapping your entity:

@Entity
public class Feature extends BaseEntity {

    // ...

    @ManyToMany(mappedBy="features")
    private Set<User> users = new HashSet<>();

    // ...
}

Then you would need to define the User <> Feature mapping:

@Entity    
public class User extends BaseEntity {
            
    // ...
    
    @ManyToMany
    @JoinTable(name="USER_FEATURE",
        joinColumns=
            @JoinColumn(name="USER_ID", referencedColumnName="ID"),
        inverseJoinColumns=
            @JoinColumn(name="FEATURE_ID", referencedColumnName="ID")
        )
    private Set<Feature> features = new HashSet<>();
    // ...
}