java-使用Hibernate将空值插入到外键字段中

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我有一个带有getter,setter方法和从问题到标签的OneToMany关系以及从问题到用户的OneToOne关系的Question实体和Tag实体

public class Question {

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

    @Column(name="title")
    private String title;

    @Column(name="body")
    private String body;

    @Temporal(TemporalType.DATE)
    @Column(name="date_created")
    private Date date_created;

    @OneToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="user_id")
    private User user;

    @OneToMany(cascade=CascadeType.ALL)
    @JoinColumn(name="tag_id")
    private Tag tag;

    @Column(name="answer_count")
    private int answer_count;

    @Column(name="view_count")
    private int view_count;

    public Question() {

}

标签实体

public class Tag {

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

    @Column(name="name")
    private String name;

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

    @Temporal(TemporalType.DATE)
    @Column(name="date_created")
    private Date date_created;

    public Tag() {

}

当我尝试使用邮递员插入具有以下详细信息的问题时：

{
    "title": "stefanyyyxx",
    "body": "stefandoyee44",
    "date_created": "2019-02-27",
    "user_id" : 1,
    "tag_id": 1,
    "answer_count": 0,
    "view_count": 0
}

QuestionRepository.java：

@Override
public void save(Question theQuestion) {

    // get the current hibernate session
    Session currentSession = entityManager.unwrap(Session.class);

    // save employee
    currentSession.saveOrUpdate(theQuestion);
}

尽管我使用JoinColumn(),但正在为user_id和tag_id插入空值.

MySQL：

解决方法:

正如@Karol Dowbecki所建议的那样,

将JSON转换为DTO对象,并使用该DTO从其各自的存储库中获取用户,标记实体.

最后,创建Question实体对象并将其存储.

问题实体

@Entity
@Table(name = "question")
public class Question {

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

    @Column(name = "title")
    private String title;

    @Column(name = "body")
    private String body;

    @Temporal(TemporalType.DATE)
    @Column(name = "date_created")
    private Date dateCreated;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "user_id")
    private User user;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "tag_id")
    private Set<Tag> tag;

    @Column(name = "answer_count")
    private int answerCount;

    @Column(name = "view_count")
    private int viewCount;

}

用户实体

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

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

    private String name;

}

标签实体

@Entity
@Table(name = "tag")
public class Tag {

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

    @Column(name = "name")
    private String name;

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

    @Temporal(TemporalType.DATE)
    @Column(name = "date_created")
    private Date dateCreated;

}

DTO等级

public class QuestionDTO {

    private Long id;

    private String title;

    private String body;

    private Date dateCreated;

    private Long user;

    private Long tag;

    private int answerCount;

    private int viewCount;
}

测试班

@Service
public class TestService {

    @Autowired
    private QuestionRepository questionRepository;

    @Autowired
    private UserRepository userRepository;

    @Autowired
    private TagRepository tagRepository;

    public void addQuestion(QuestionDTO dto) {
        Tag tag = null;
        User user = null;
        Question question = null;

        Set<Tag> tags = null;

        tag = tagRepository.findById(dto.getTag());

        tags = new HashSet<>();
        tags.add(tag);

        user = userRepository.findById(dto.getUser());

        question = new Question();
        question.setTag(tags);
        question.setUser(user);
        question.setId(dto.getId());
        question.setBody(dto.getBody());
        question.setTitle(dto.getTitle());
        question.setViewCount(dto.getViewCount());
        question.setAnswerCount(dto.getAnswerCount());
        question.setDateCreated(dto.getDateCreated());

        questionRepository.save(question);

    }
}

注意 ：
Question和Tag之间的关系在OneToMany中,您必须使用Collection类型.

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