Java JPA Hibernate删除实体关系中的孤立项

我对JPA有问题。我无法从数据库中删除staff对象，如下所示：

// trying to delete from my jsp this person-staff (commit error)
Staff del = em.find(Staff.class, staff.getId());    
em.getTransaction().begin();
em.remove(del);
em.getTransaction().commit();
em.close();
emf.close();

或者改变它：

Staff staff... // get changed data from html form
MyCompositePK temp = new MyCompositePK();
String[] parts = author.split(" ");
temp.setFirstName(parts[0]);
temp.setSurname(parts[1]);
temp.setPatronymic(parts[2]);
Staff change = (Staff) em.find(Staff.class, temp); 

em.getTransaction().begin(); 
change.setId(staff.getId());
em.getTransaction().commit();
em.close();
emf.close();

MyCompositePK是Staff类的嵌入id。以下是我的实体：

@Embeddable
public class MyCompositePK implements Serializable {

    @Column
    private String surname;
    @Column
    private String firstName;
    @Column
    private String patronymic;

    //getters and setters
}

以下是员工等级声明：

//imports

@Entity
public class Staff {

    @EmbeddedId
    private MyCompositePK id;
    private Date birthday;
    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumn(name="POST_ID")
    private Post post;
    @Lob
    @Column(length = 100000)
    private byte[] photo;

    //getters and setters
}

这是我的文档（我还有另外两个文档，它们继承文档类），其中包含带有Staff（manytone）的字段

---

那么，我可以直接删除Staff对象吗

您是否为

MyCompositePK

定义了

hashCode（）

和

equals（）

方法？否。它们不是必需的。据我所知，您可以在您的想法中切换到警告，它们必须为复合键定义。您是否为

MyCompositePK

定义了

hashCode（）

和

equals（）

方法？否。它们不是强制性的。据我所知，您可以在您的想法中切换到警告，它们必须为复合键定义。

package documents;

//imports    

@Entity
@Table(name = "incomings")
public class Incoming extends Document {    

    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumns({ @JoinColumn(name = "sender_firstname",    referencedColumnName = "firstname"),
            @JoinColumn(name = "sender_surname", referencedColumnName = "surname"),
            @JoinColumn(name = "sender_patronymic", referencedColumnName = "patronymic") })
    private Staff sender;

    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumns({ @JoinColumn(name = "destination_firstname", referencedColumnName = "firstname"),
            @JoinColumn(name = "destination_surname", referencedColumnName = "surname"),
            @JoinColumn(name = "destination_patronymic", referencedColumnName = "patronymic") })
    private Staff destination;

    private int outgoingNumber;     
    private Date outgoingRegDate;

    //getters and setters

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Входящий документ" + "\r\n");
        sb.append(super.toString());
        sb.append("Отправитель" + sender.toString() + "\r\n");
        sb.append("Адресат" + destination.toString() + "\r\n");
        sb.append("Исходящий номер" + outgoingNumber + "\r\n");
        sb.append("Исходящая дата регистрации" + outgoingRegDate.toString() + "\r\n");
        sb.append("Текст документа" + super.getContent() + "\r\n");
        return sb.toString();
    }
}