Java 父子关系-自联接映射

我正在尝试构建一个应用程序，它将接收包含员工列表的XML文件，并将父-子/员工-经理关系存储在单个数据库表中

我的XML文件如下所示：

<Employees>
    <Employee manager="Patrick">Martin</Employee>
    <Employee manager="Patrick">Kent</Employee>
    <Employee manager="Martin">Mark</Employee>
    <Employee>Hugo</Employee> <!-- root element of the employee-manager tree -->
    <Employee manager="Hugo">Osa</Employee>
    <Employee manager="Osa">Patrick</Employee>
</Employee>

我创建了一个名为

Employee

的新类，但我不确定如何定义适当的多通/OneToMany注释

由于我对这方面还不太熟悉，所以我在谷歌上搜索了一些示例和教程（以及关于堆栈溢出的类似问题的答案），但我想我在定义这个模型时在这个实现中犯了一些大错误。我最近的尝试如下所示：

public class Employee {
    @Id
    @GeneratedValue
    private int id;

    @Column(name = "parent_id")
    @Transient
    @ManyToOne(cascade={CascadeType.ALL})
    private String managerName;

    @Column(name = "employee_name")
    @JoinColumn(name="parent_id")
    private String employeeName;

    // getters and setters

@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="manager_id")
private Employee manager;

@OneToMany(mappedBy="manager")
private Set<Employee> subordinates = new HashSet<Employee>();

@Column(name = "employee_name")
private String employeeName;

@Entity
@Table(name = "EMPLOYEE")
public class Employee {

    @Id
    @GeneratedValue
    private int id;

    @ManyToOne
    private Employee manager;

    @Column(name = "employee_name")
    private String employeeName;

---

如果有人能为我指出定义合适模型的方向，我将非常感谢

在

Hibernate

中，当您想要映射

manytone

关系时，您需要在实体之间映射它，而不仅仅是属性，因此您需要引用

Employee

类型的对象，而不仅仅是

字符串或
id

问题：


因此，您的映射不正确，会引发许多映射错误，
而不是写：

@Column(name = "parent_id")
@Transient
@ManyToOne(cascade={CascadeType.ALL})
private String managerName;

您需要像这样映射
manytone
关系：

public class Employee {
    @Id
    @GeneratedValue
    private int id;

    @Column(name = "parent_id")
    @Transient
    @ManyToOne(cascade={CascadeType.ALL})
    private String managerName;

    @Column(name = "employee_name")
    @JoinColumn(name="parent_id")
    private String employeeName;

    // getters and setters

@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="manager_id")
private Employee manager;

@OneToMany(mappedBy="manager")
private Set<Employee> subordinates = new HashSet<Employee>();

@Column(name = "employee_name")
private String employeeName;

@Entity
@Table(name = "EMPLOYEE")
public class Employee {

    @Id
    @GeneratedValue
    private int id;

    @ManyToOne
    private Employee manager;

    @Column(name = "employee_name")
    private String employeeName;


并确保映射关系的另一面，如下所示：

public class Employee {
    @Id
    @GeneratedValue
    private int id;

    @Column(name = "parent_id")
    @Transient
    @ManyToOne(cascade={CascadeType.ALL})
    private String managerName;

    @Column(name = "employee_name")
    @JoinColumn(name="parent_id")
    private String employeeName;

    // getters and setters

@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="manager_id")
private Employee manager;

@OneToMany(mappedBy="manager")
private Set<Employee> subordinates = new HashSet<Employee>();

@Column(name = "employee_name")
private String employeeName;

@Entity
@Table(name = "EMPLOYEE")
public class Employee {

    @Id
    @GeneratedValue
    private int id;

    @ManyToOne
    private Employee manager;

    @Column(name = "employee_name")
    private String employeeName;


@Transient
在您的映射中是无用的，我们只在
希望使用不会在数据库中持久化的属性

最重要的是，确保将类映射到
@Entity
，这样它就可以
保存在数据库中


示例：

您可以检查它是否使用了您想要实现的相同模型。
您只需与Employee表有一个manytone关系，即多个员工可以拥有同一个经理（同时也是员工），对于经理，此字段将保持为空，如下所示：

public class Employee {
    @Id
    @GeneratedValue
    private int id;

    @Column(name = "parent_id")
    @Transient
    @ManyToOne(cascade={CascadeType.ALL})
    private String managerName;

    @Column(name = "employee_name")
    @JoinColumn(name="parent_id")
    private String employeeName;

    // getters and setters

@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="manager_id")
private Employee manager;

@OneToMany(mappedBy="manager")
private Set<Employee> subordinates = new HashSet<Employee>();

@Column(name = "employee_name")
private String employeeName;

@Entity
@Table(name = "EMPLOYEE")
public class Employee {

    @Id
    @GeneratedValue
    private int id;

    @ManyToOne
    private Employee manager;

    @Column(name = "employee_name")
    private String employeeName;

谢谢，chsdk。我将尝试按照您提出的方式实施解决方案。希望我能做到。@hezus不客气，我相信它会给你预期的结果。