Hibernate继承策略=InheritanceType.Jointed&onetoMany with spring-data-jpa

Question

由于某些原因，我无法使Hibernate继承策略=InheritanceType.Joint&onetoMany的组合工作。以下是这些实体。

@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@DiscriminatorColumn(name="OBJECT_TYPE")
public abstract class ExamObject {

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

        @ManyToOne(fetch = FetchType.LAZY)
        @JoinColumn(name = "examid", nullable = false)
        private Exam exam;
}

@Entity
@DiscriminatorValue("Q")
public class ExamQuestion extends ExamObject{

     private Integer questionNumber;

     private String questionDesc;
}

@实体

public class Exam {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer examid;

    private String examName;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "exam")
    private Set<ExamObject> object
}

@SpringBootApplication
public class ExamApp implements CommandLineRunner {
@Autowired
    private ExamQuestionRepository examQuestionRepository;

    @Autowired
    private ExamRepository examRepository;

    public static void main(String[] args) {
        SpringApplication.run(ExamApp.class, args);
    }


    @Override
    @Transactional
    public void run(String... arg0) throws Exception {
        Exam exam = new Exam();
        exam.setExamName("Exam1");
        examRepository.save(exam);

        String[] questions = new String[]{"Question1,Question2"};
        ArrayList<ExamQuestion> examQuestions = new ArrayList<ExamQuestion();
        int index = 0;
        for(String questionNoDesc: questions){
            index++;
            ExamQuestion examQuestion = new ExamQuestion();
            examQuestion.setQuestionDesc(questionNoDesc);
            examQuestion.setQuestionNumber(index);
            examQuestion.setExam(exam);
            examQuestions.add(examQuestion);
        }
        examQuestionRepository.save(examQuestions);

        Iterable<Exam> examGet = examRepository.findAll();
        for (Exam exam2: examGet) {
             System.out.println("Exam question is .. " +exam2.getObjects());
        }
    }
 }

Answer 1

正如在原问题的注释中所解释的，问题是对象图没有得到正确的维护。以下函数的一个额外代码行修复了这个问题。Exam.SetObjects（examQuestions）；已添加

@Override
    @Transactional
    public void run(String... arg0) throws Exception {
        Exam exam = new Exam();
        exam.setExamName("Exam1");
        examRepository.save(exam);

        String[] questions = new String[]{"Question1,Question2"};
        ArrayList<ExamQuestion> examQuestions = new ArrayList<ExamQuestion();
        int index = 0;
        for(String questionNoDesc: questions){
            index++;
            ExamQuestion examQuestion = new ExamQuestion();
            examQuestion.setQuestionDesc(questionNoDesc);
            examQuestion.setQuestionNumber(index);
            examQuestion.setExam(exam);
            examQuestions.add(examQuestion);
        }
        examQuestionRepository.save(examQuestions);
        exam.setObjects(examQuestions);

        Iterable<Exam> examGet = examRepository.findAll();
        for (Exam exam2: examGet) {
             System.out.println("Exam question is .. " +exam2.getObjects());
        }
    }