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Question

Suppose such a mapping

@Entity
public class User {

    private Integer id

    private List<Info> infoList;    

    @Id
    public getId() {
        return this.id;
    }

    @OneToMany(cascade=CascadeType.ALL)
    @JoinColumn(name="USER_ID", insertable=false, updateable=false, nullable=false)
    public getInfoList() {
        return this.infoList;
    }

    public void addQuestion(Info question) {
        info.setInfoCategory(InfoCategory.QUESTION);
        info.setInfoId(new InfoId(getId(), getInfoList().size()));

        getInfoList().add(question);
    }

    public void addAnswer(InfoRepository repository, Integer questionIndex, Info answer) {
        Info question = repository.getInfoById(new InfoId(getId(), questionIndex));

        if(question.getInfoCategory().equals(InfoCategory.ANSWER))
            throw new RuntimeException("Is not a question");

        if(question.getAnswer() != null)
            throw new RuntimeException("You can not post a new answer");

        answer.setInfoCategory(InfoCategory.ANSWER);
        answer.setInfoId(new InfoId(getId(), getInfoList().size()));

        getInfoList().add(answer);

        question.setAnswer(answer);
    }

}

And the question and answer matched by the Info class

@Entity
public class Info implements Serializable {

    private InfoId infoId;

    private Info answer;

    private InfoCategory infoCategory;

    public Info() {}

    @Embeddable
    public static class InfoId {

        private Integer userId;
        private Integer index;

        public InfoId(Integer userId, Integer index) {
            this.userId = userId;
            this.index = index;
        }

        @Column("USER_ID", updateable=false, nullable=false)
        public getUserId() {
            return this.userId;
        } 

        @Column("INFO_INDEX", updateable=false, nullable=false)
        public getIndex() {
            return this.index;
        }

        // equals and hashcode

    }

    // mapped as a ManyToOne instead of @OneToOne
    @ManyToOne
    JoinColumns({
        JoinColumn(name="USER_ID", referencedColumnName="USER_ID", insertable=false, updateable=false),
        JoinColumn(name="ANSWER_INDEX", referencedColumnName="INFO_INDEX", insertable=false)
    })
    public Info getAnswer() {
        return this.answer;  
    }

    @EmbeddedId
    public InfoId getInfoId() {
        return this.infoId;
    }

}

In getAnswer, I use ManyToOne instead of OneToOne because some problems are related to the display of OneToOne. OneToOne can be displayed as ManyToOne (unique = true in @JoinColumn). INFO_INDEX is not related to any specific purpose. Just a key to support a composite primary key in a LEGACY system.

Before answering, take care of the following:

If the object has an assigned identifier or composite key, the identifier MUST BE ASSIGNED to the object instance BEFORE calling save ()

, JoinColumn (name= "USER_ID", referedColumnName = "USER_ID", insertable = false, updateable = false) getAnswer, Hibernate (userId USER_ID ) USER_ID answer, insertable = false, updateable = false

getAnswer

@ManyToOne
JoinColumns({
    JoinColumn(name="USER_ID", referencedColumnName="USER_ID", insertable=false, updateable=false),
    JoinColumn(name="ANSWER_INDEX", referencedColumnName="INFO_INDEX", insertable=false)
})

, Hibernate ,

, ?

, LEGACY.

,

Answer 1

getAnswer

@ManyToOne
JoinColumns({
    JoinColumn(name="USER_ID", referencedColumnName="USER_ID", insertable=false, updateable=false),
    JoinColumn(name="ANSWER_INDEX", referencedColumnName="INFO_INDEX", insertable=false)
})

Hibernate , . USER_ID JoinColumn ANSWER_INDEX JoinColumn.

, , ANSWER_INDEX JoinCollumn accortding

JoinColumn(name="ANSWER_INDEX", referencedColumnName="INFO_INDEX", insertable=false, updateable=false)

, Hibernate .

, answerIndex

private Integer answerIndex;   

@Column(name="ANSWER_INDEX", insertable=false)
public void getAnswerIndex() {
    return this.answerIndex;
}

User addAnswer

public void addAnswer(InfoRepository repository, Integer questionIndex, Info answer) {
    Info question = repository.getInfoById(new InfoId(getId(), questionIndex));

    if(question.getInfoCategory().equals(InfoCategory.ANSWER))
        throw new RuntimeException("Is not a question");

    if(question.getAnswer() != null)
        throw new RuntimeException("You can not post a new answer");

    answer.setInfoCategory(InfoCategory.ANSWER);
    answer.setInfoId(new InfoId(getId(), getInfoList().size()));

    getInfoList().add(answer);

    // Added in order to set up AnswerIndex property
    question.setAnswerIndex(answer.getInfoId().getIndex());
}

Answer 2

, id PK.

InfoId.index - ( /? , list mapping), .

UserId ManyToOne User; ( User) @OneToMany(mappedBy="User")

ManyToOne? OneToMany (, )? , - "", ; , . Question Answer ; ( ) ; , Hibernate.