Quarkus中Hibernate with Panache关联实体持久化外键为空问题解决

问题场景 #

在Quarkus项目中使用Hibernate with Panache，存在一对多关联的QuestionGroup和Question实体。执行批量插入QuestionGroup及其关联Question时，QuestionGroup可正常持久化，但Question报错Column 'question_group_id' cannot be null，要求在不分开持久化两类实体的前提下解决该问题。

实体类代码 #

QuestionGroup.java

@Entity
@Table(name = "tb006_question_groups")
public class QuestionGroup {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "question_group_id")
    @Getter @Setter
    private Long id;

    @Column(name = "question_group_code")
    @Getter @Setter
    private String code;

    @Column(name = "question_group_name")
    @Getter @Setter
    private String name;

    @CreationTimestamp
    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "question_group_createdAt")
    @Getter @Setter
    private Date createdAt;

    @UpdateTimestamp
    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "question_group_updatedAt")
    @Getter @Setter
    private Date updatedAt;

    @Column(name = "question_group_enabled")
    @Getter @Setter
    private Integer enabled;

    @OneToMany(mappedBy="questionGroup", cascade = CascadeType.PERSIST)
    @Getter @Setter
    private List<Question> questions;
}

Question.java

@Entity
@Table(name = "tb007_questions")
public class Question {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "question_id")
    @Getter @Setter
    private Long id;

    @Column(name = "question_name")
    @Getter @Setter
    private String name;

    @Column(name = "question_answer")
    @Getter @Setter
    private String answer;

    @CreationTimestamp
    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "question_createdAt")
    @Getter @Setter
    private Date createdAt;

    @UpdateTimestamp
    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "question_updatedAt")
    @Getter @Setter
    private Date updatedAt;

    @Column(name = "question_enabled")
    @Getter @Setter
    private Integer enabled;

    @ManyToOne
    @JoinColumn(name="question_group_id", nullable=false)
    @Getter @Setter
    private QuestionGroup questionGroup;
}

原插入方法 #

@Transactional
@Override
public QuestionGroup createQuestionGroup(QuestionGroupCreateRequestDTO questionGroupCreate) {
        QuestionGroup questionGroup = 
        this.convertQuestionGroupCreateToQuestionGroup(questionGroupCreate);
        if (questionGroupCreate.getQuestions() != null) {
            List<Question> questions = questionGroupCreate.getQuestions().stream().map(question -> this.convertQuestionCreateToQuestion(question)).collect(Collectors.toList());
            questionGroup.setQuestions(questions);
        }
        questionGroupRepository.persist(questionGroup);
        return questionGroup;
    }

解决方案 #

问题核心是双向关联未维护双方关系：JPA中双向关联的外键维护权在拥有@ManyToOne的一方（即Question），仅设置QuestionGroup的questions列表，未给每个Question绑定对应的questionGroup引用，导致Hibernate无法识别关联关系，插入Question时外键字段为空。

修改插入方法，在转换QuestionDTO为实体时，同步设置其questionGroup属性：

@Transactional
@Override
public QuestionGroup createQuestionGroup(QuestionGroupCreateRequestDTO questionGroupCreate) {
        QuestionGroup questionGroup = this.convertQuestionGroupCreateToQuestionGroup(questionGroupCreate);
        if (questionGroupCreate.getQuestions() != null) {
            List<Question> questions = questionGroupCreate.getQuestions().stream()
                    .map(questionDTO -> {
                        Question question = this.convertQuestionCreateToQuestion(questionDTO);
                        // 维护双向关联：给Question绑定对应的QuestionGroup
                        question.setQuestionGroup(questionGroup);
                        return question;
                    })
                    .collect(Collectors.toList());
            questionGroup.setQuestions(questions);
        }
        questionGroupRepository.persist(questionGroup);
        return questionGroup;
    }

原理说明 #

尽管QuestionGroup的ID采用IDENTITY策略（persist后才生成），但Hibernate处理级联PERSIST时，会先保存QuestionGroup获取生成的ID，再自动将该ID填充到关联Question的question_group_id字段中——前提是两者的双向关联关系已正确建立。

内容的提问来源于stack exchange，提问作者nilsonjr