jpa中实体类的一对多和多对一注解如何使用

关于JPA中实体类的一对多和多对一注解的使用，请参考如下内容：

@OneToMany注解用来定义实体间的一对多关系，示例代码如下：

@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
private List<Address> addresses = new ArrayList<>();
}

@Entity
@Table(name = "address")
public class Address {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@ManyToOne
@JoinColumn(name = "user_id")
private User user;
}

@ManyToOne注解用来定义实体间的多对一关系，示例代码如下：

@Entity
@Table(name = "address")
public class Address {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "user_id")
private User user;
}

@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
private List<Address> addresses = new ArrayList<>();
}

希望这些信息能对你有所帮助。