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问题：

我在父母和孩子之间有一个@OneToOne关系，该关系由孩子映射，并且 orphanRemoval设置为true。孩子还与第三个实体有@ManyToMany 关系。

将孩子设置为空（希望删除孩子）时，我得到一个完整性约束违规：外键...

测试型号：

Tutor与Student具有OneToOne 关系， Student 与Course实体具有 ManyToMany 关系：

  • OneToOne 关系由 Student.tutor 映射（STUDENT 表中的 ID_TUTOR 外键列）
    • 级联 = 全部
    • 孤儿移除 = 真
  • ManyToMany 关系保存在连接表 STUDENT_COURSE 中，外键指向 STUDENT 和 COURSE 表。

我正在使用休眠 5.0.11 (JPA 2.1)。对于我的测试，我使用了 HSQLDB，但问题也出现在 Oracle 数据库上。

设想：

我有一个导师链接到一个包含课程列表的学生。当设置Tutor的Student为null时，Hibernate直接发出SQL“ delete from Student where id=? ”导致“完整性约束违规：外键无动作；FK1XM2HEI9CHMWOQF2WFM104NMG表：STUDENT_COURSE”

当 OneToMany 关系未“反转”（TUTOR 表中没有mappedBy和 ID_STUDENT 外键）时，不会发生此问题。在这种情况下，Student 实体以及 STUDENT_COURSE 表中的相关记录已正确地从 DB 中删除。

代码：

@Entity
public class Tutor {
    private Long id;
    private String name;
    private Student student;
    public Tutor() { super(); }
    public Tutor(String name, Student student) {
        super();
        this.name = name;
        setStudent(student);
    }
    @Id
    @GeneratedValue
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    @OneToOne(cascade=CascadeType.ALL, orphanRemoval=true, mappedBy="tutor")
    public Student getStudent() { return student; }
    public void setStudent(Student student) {
        this.student = student;
        if(student != null) {
            student.setTutor(this);
        }
    }
}

@Entity
public class Student {
    private Long id;
    private String name;
    private Map<String, Course> courses;
    private Tutor tutor;
    public Student() { super(); }
    public Student(String name, Map<String, Course> courses) {
        super();
        this.name = name;
        this.courses = courses;
    }
    @Id
    @GeneratedValue
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    @ManyToMany
    public Map<String, Course> getCourses() { return courses; }
    public void setCourses(Map<String, Course> courses) { this.courses = courses; }
    @OneToOne
    public Tutor getTutor() { return tutor; }
    public void setTutor(Tutor tutor) { this.tutor = tutor; }   
}

@Entity
public class Course {
    private Long id;
    private String name;
    public Course() { super(); }
    public Course(String name) {
        super();
        this.name = name;
    }
    @Id
    @GeneratedValue
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

public class CheckManyToManyDeletation {
    private static final Logger logger = Logger.getLogger(CheckManyToManyDeletation.class);
    private static SessionFactory sessionFactory;
    public static void main(String[] args) {
        DOMConfigurator.configure("log4j-config.xml");
        Class[] mappings =  new Class[] {Tutor.class, Student.class, Course.class};
        DBUtils.createTables(mappings);
        sessionFactory = DBUtils.createSessionFactory(mappings);
        try {
            long tutorId = initialImport();

            Session session = sessionFactory.openSession();
            Transaction tx = session.beginTransaction();

            Tutor tutor = session.get(Tutor.class, tutorId);
            logger.info("DeletingStudent");
            tutor.setStudent(null);

            tx.commit();
        } finally {
            sessionFactory.close();
        }

    }

    private static long initialImport() {
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        Student student = new Student();
        student.setName("student");

        Map<String, Course> courses = new HashMap<>();
        student.setCourses(courses);
        for (int i = 0; i < 5; i++) {
            Course course = new Course();
            course.setName("course" + i);
            session.save(course);
            courses.put(course.getName(), course);
        }

        Tutor tutor = new Tutor("tutor", student);
        session.save(tutor);
        tx.commit();
        session.close();
        return tutor.getId();
    }
}

笔记：

实际上，我们的应用程序带有一个巨大的数据模型：

  • 持久化和删除实体是通过级联完成的，
  • 我们反转 OneToOne 关系以赋予子代与其父代相同的 id（通过 @MapsId）。
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