使用MySQL DB在Hibernate单向中进行一对一映射？

Question

Am new to Hibernate and MySQL, i have two Table like OFFER_TABLE and OFFER_LIKES_DISLIKES

OFFER_TABLE Columns

OFR_ID(PK)
OFR_MSG

OFFER_LIKES_DISLIKES Columns

OFFER_LIKES_DISLIKES_ID
OFR_ID(FK)
LIKE
DISLIKE

I want to map OFFER_TABLE and OFFER_LIKES_DISLIKES, Access the OFFER_LIKES_DISLIKES data through OFFER_TABLE. Am using One to One Mapping but its not Working.

Hibernate Annotation Mapping Java Class

Offers.class

@Id
@GeneratedValue
@Column(name = "OFR_ID", length = 11, nullable = false)
private int offer_id;

@OneToOne
@JoinColumn(name="OFR_ID", unique = true)
@OneToOne(cascade = CascadeType.ALL)
private MessageLikeDislikesDAO likeDislikes;

LikeDislike.class

@GeneratedValue
@Column(name="LIKES_DISLIKES_ID", length = 11, nullable = false)
private int likes_dislikes_id;

@Expose
@Column(name="OFR_ID", length = 11, nullable = false)
private int offer_id;

When I get the Data of Offers, want Like and Dislike data associated with it. In LikeDislike table OFR_ID is UNIQUE. Am used One to One. But i didn't get the data of LikeDislike. Which one is best way to took that data. Help me to solve this issue.

Answer 1

There are many problems:

1. You're creating an association with a DAO instead of creating an association with an entity
2. You're storing the ID of the offer in the LikeDislike entity instead of storing an association with the Offer entity
3. You're saying that there is a join column named OFR_ID and referring to the LikeDislike entity in the OFFER table .
4. You disrespect Java naming conventions
5. You're setting two OneToOne annotations on the same field

The mapping should be:

Offer:

@Id
@GeneratedValue
@Column(name = "OFR_ID", length = 11, nullable = false)
private Integer offerId;

@OneToOne(mappedBy = "offer", cascade = CascadeType.ALL)
private LikeDislike likeDislike;

LikeDislike:

@GeneratedValue
@Column(name="LIKES_DISLIKES_ID", length = 11, nullable = false)
private Integer likeDislikeId;

@Expose
@OneToOne
@JoinColumn(name="OFR_ID", length = 11, nullable = false)
private Offer offer;

Relevant documentation