CODEWITHSUNDEEP
javahibernateforeign-key-relationship
user3173237
user3173237

Reputation: 111

Foreign Key Hibernate Annotation

I can not manage to make this simple foreign key constraint work.

@Entity
@Table(name = "wheel")
@Data
public class WheelEntity {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    ...

@Entity
@Table(name = "bike")
@Data
public class BikeEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @ManyToOne(targetEntity = WheelEntity.class, fetch=FetchType.EAGER, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
    @JoinColumn(name = "wheel_1_id", referencedColumnName = "id")
    @NotNull
    private Integer wheel_1_id;

    @ManyToOne(targetEntity = WheelEntity.class, fetch=FetchType.EAGER, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
    @JoinColumn(name = "wheel_2_id", referencedColumnName = "id")
    @NotNull
    private Integer wheel_2_id;
    ...

When I want to insert a new bike, here is the error I get when persisting the BikeEntity:

Caused by: java.lang.IllegalArgumentException: Can not set java.lang.Integer field com.xxx.xxx.xxx.storage.WheelEntity.id to java.lang.Integer
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
    at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
    at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
    at java.lang.reflect.Field.get(Field.java:393)
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:39)

Can not set java.lang.Integer to java.lang.Integer. mmmmmm? Strange!

Many thanks for the help

Upvotes: 2

Views: 6034

Answers (1)

Jay Smith
Jay Smith

Reputation: 2480

In hibernate you create relation by having reference of Entity1 inside Entity2. The correct way is:

@Entity
@Table(name = "wheel")
@Data
public class WheelEntity {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    ...

@Entity
@Table(name = "bike")
@Data
public class BikeEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @ManyToOne(targetEntity = WheelEntity.class, fetch=FetchType.EAGER, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
    @JoinColumn(name = "wheel_1_id", referencedColumnName = "id")
    @NotNull
    private WheelEntity wheelEntity;

Upvotes: 2

Related Questions