Question

我有两个具有多对多关系的表，它们具有如下所示的JoinTable USER_SERVICES。

@Entity
public class User implements Serializable {

    @NotNull
    @Column(unique=true)
    private String username;

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

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(
            name = "USER_SERVICES",
            joinColumns = {@JoinColumn(name = "id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name = "", referencedColumnName = "name")})
    private Set<Services> services;

    // Getters and Setters
}   


@Entity
public class Services implements Serializable {

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

    @NotNull
    @Column(unique=true)
    private String name;

    //Getters and Setters

}

上面的代码创建了一个表USER_SERVICES，但我还想在表USER_SERVICES上与另一个表RATINGS建立多对多关系，这将导致另一个表USER_SERVICES_RATINGS。如何用Hibernate / JPA注释定义这种关系？

Answer 1

使用用户管理的联接表对象的多向双向（相对常见）

通常用于存储关于连接对象的额外信息，例如创建关系的日期。

public class Foo{
    private UUID fooId;

    @OneToMany(mappedBy = "bar", cascade=CascadeType.ALL)
    private List<FooBar> bars;
}

public class Bar{
    private UUID barId;

    @OneToMany(mappedBy = "foo", cascade=CascadeType.ALL)
    private List<FooBar> foos;
}

@Entity
@Table(name="FOO_BAR")
public class FooBar{
    private UUID fooBarId;

    @ManyToOne
    @JoinColumn(name = "fooId")
    private Foo foo;

    @ManyToOne
    @JoinColumn(name = "barId")
    private Bar bar;

    //You can store other objects/fields on this table here.
}

Answer 2

您需要创建一个明确的UserServices实体，并根据您的需要设置与Ratings实体的关系。

请记住，在hibernate中，您可以建模实体之间的关系（即您的java对象），而不是db表。

Hibernate在@JoinTable上创建关系

2 个答案: