Inheritance 如何使用级联删除删除JPA中的继承类？

这个问题可能有点让人困惑，所以我会尝试用一些例子来说明

我正在使用JPA2.0和Eclipselink 2.2

我有三门课，个人，学生和证书，它们之间有这种关系：

• 学生从Person继承（扩展）
• 学生有证书（@OneToOne）

我的类定义如下：

Person.java

@Entity
@Table(name = "person")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING, length = 20)
@DiscriminatorValue("person")
public abstract class Person {

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

    private String firstName;
    private String lastName;
    private String street;
    private String city;
    private String zipCode;
    private String phoneNumber;

    /*Getters and Setters*/

}

@SuppressWarnings("serial")
@Entity
@Table(name = "student")
@DiscriminatorValue("student")
public class Student extends Person implements Serializable {

    @Column(unique = true)
    private String studentId;

    @OneToOne(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true, optional = false, mappedBy = "student")
    @CascadeOnDelete
    private Credentials credentials;

    /*Getters and Setters*/
}

@SuppressWarnings("serial")
@Entity
public class Credentials implements Serializable {

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

    @Column(unique = true)
    private String username;

    private String password;

    private Student student;
}

Student.java

@Entity
@Table(name = "person")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING, length = 20)
@DiscriminatorValue("person")
public abstract class Person {

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

    private String firstName;
    private String lastName;
    private String street;
    private String city;
    private String zipCode;
    private String phoneNumber;

    /*Getters and Setters*/

}

@SuppressWarnings("serial")
@Entity
@Table(name = "student")
@DiscriminatorValue("student")
public class Student extends Person implements Serializable {

    @Column(unique = true)
    private String studentId;

    @OneToOne(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true, optional = false, mappedBy = "student")
    @CascadeOnDelete
    private Credentials credentials;

    /*Getters and Setters*/
}

@SuppressWarnings("serial")
@Entity
public class Credentials implements Serializable {

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

    @Column(unique = true)
    private String username;

    private String password;

    private Student student;
}

Credentials.java

@Entity
@Table(name = "person")
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING, length = 20)
@DiscriminatorValue("person")
public abstract class Person {

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

    private String firstName;
    private String lastName;
    private String street;
    private String city;
    private String zipCode;
    private String phoneNumber;

    /*Getters and Setters*/

}

@SuppressWarnings("serial")
@Entity
@Table(name = "student")
@DiscriminatorValue("student")
public class Student extends Person implements Serializable {

    @Column(unique = true)
    private String studentId;

    @OneToOne(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true, optional = false, mappedBy = "student")
    @CascadeOnDelete
    private Credentials credentials;

    /*Getters and Setters*/
}

@SuppressWarnings("serial")
@Entity
public class Credentials implements Serializable {

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

    @Column(unique = true)
    private String username;

    private String password;

    private Student student;
}

问题是当我试图删除一个学生时

        entityManager.getTransaction().begin();
        entityManager.remove(student);
        entityManager.getTransaction().commit();

出现此约束（我可以发布更多错误消息，但这似乎是关键）：

我已经尝试过几次助教，一个方向，学生和证书之间的双向关系，但结果几乎都是一样的

如何删除学生实体

---

非常感谢您提供的任何帮助。

不回答您的问题，但由于Person类中没有关系，因此您可以使用mappedSuperClass而不是InherInstance（以获得更好的性能）因为Person是抽象的：我看不出有任何理由在Person类中定义鉴别器值。只有在数据库中的关系上设置了cascade delete时，才能使用cascade delete注释。设置它意味着当数据库删除学生时，它还将负责删除凭据。由于没有发生这种情况，您可能没有在数据库中设置级联删除。删除注释，JPA将为您执行删除操作，或者更改数据库-您可以让EclipseLink DDL删除并为您重新创建数据库EclipseLink 2.4我相信indluce会在生成的DDL@ben75很抱歉，在尝试做一些测试时，抽象描述被放在了后面。我也尝试过

@MappedSuperclass

，但得到了相同的结果。@Chris我的数据库完全是通过persistence.xml文件生成的。我放置了一些伪代码，并使用

语法在开发过程中重建结构。我没有运气手动删除这些表。