如何保留两个对象，但只更新一个，如果它已经存在

Question

我基本上有一个预订系统，包括预订、员工和客户。

我想保留一个预订实体。预订实体有一个员工（将提供服务）和一个客户（预订是为其发生的）。

我希望能够保留一个预订对象，如果该对象已经存在，则不会在其中创建员工和/或客户。我如何通过JPA和hibernate实现这一点。

我还想保留我现有的模式（预订表、员工表、客户表以及预订客户、预订员工之间的关系表…）

以下是预订实体：

@Entity
@Table(name = "bookings")
@EntityListeners(AuditingEntityListener.class)
public class Booking
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "booking_id")
    private Long id;

    @Column(name = "title")
    private String title;

    @Column(name = "description")
    private String description;

    @Column(name = "service")
    private String service;

    @NotNull(message = "status is mandatory")
    @Column(name = "status")
    @Enumerated(EnumType.STRING)
    private BookingStatus status;

    @Column(name = "scheduled_at", nullable = false)
    private LocalDateTime scheduledAt;

    @Column(name = "created_at")
    @CreationTimestamp
    private LocalDateTime createdAt;

    @Column(name = "updated_at")
    @UpdateTimestamp
    private LocalDateTime updatedAt;

    @ManyToOne(fetch = FetchType.EAGER, cascade=CascadeType.ALL)
    @JoinTable(name = "booking_customer", joinColumns = {@JoinColumn(name = "booking_id")}, inverseJoinColumns = {@JoinColumn(name = "customer_id")})
    private Customer customer;

    @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.PERSIST)
    @JoinTable(name = "booking_employee", joinColumns = {@JoinColumn(name = "booking_id")}, inverseJoinColumns = {@JoinColumn(name = "employee_id")})
    private Employee employee;

    @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.PERSIST)
    @JoinTable(name = "booking_address", joinColumns = {@JoinColumn(name = "booking_id")}, inverseJoinColumns = {@JoinColumn(name = "address_id")})
    private Address address;
}

这里是客户实体：

@Entity
@Table(name = "customers")
@EntityListeners(AuditingEntityListener.class)
public class Customer
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "customer_id")
    private Long id;

    @NotBlank(message = "firstName is mandatory")
    @Column(name = "first_name")
    private String firstName;

    @NotBlank(message = "lastName is mandatory")
    @Column(name = "last_name")
    private String lastName;

    @NotBlank(message = "email is mandatory")
    @Column(name = "email_address")
    private String email;

    @NotBlank(message = "phoneNumber is mandatory")
    @Column(name = "phone_number")
    private String phoneNumber;

    @Column(name = "created_at")
    @CreationTimestamp
    private LocalDateTime createdAt;

    @Column(name = "updated_at")
    @UpdateTimestamp
    private LocalDateTime updatedAt;

    @OneToMany(mappedBy = "customer", cascade=CascadeType.ALL, fetch = FetchType.EAGER)
    private List<Booking> bookings;
 }

这里是雇员实体：

@Entity
@Table(name = "employees")
@EntityListeners(AuditingEntityListener.class)
public class Employee
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "employee_id")
    private Long id;

    @NotBlank(message = "firstName is mandatory")
    @Column(name = "first_name")
    private String firstName;

    @NotBlank(message = "lastName is mandatory")
    @Column(name = "last_name")
    private String lastName;

    @Column(name = "email_address")
    private String email;

    @NotBlank(message = "phoneNumber is mandatory")
    @Column(name = "phone_number")
    private String phoneNumber;

    @Column(name = "created_at")
    @CreationTimestamp
    private LocalDateTime createdAt;

    @Column(name = "updated_at")
    @UpdateTimestamp
    private LocalDateTime updatedAt;

    @OneToMany(mappedBy = "employee", cascade=CascadeType.ALL, fetch = FetchType.EAGER)
    private List<Booking> bookings;

}

为了清晰起见，我去掉了getter和setter。

我想能够坚持与客户和员工通过邮递员这样的预订

{
    "title": "Haircut & Beards with Aymen",
    "description": "I would like to clean shave my head",
    "service": "COUPE-12 Haircut",
    "status": "PENDING",
    "scheduledAt": "2021-08-10T15:50:05.609",
    "customer": {
        "firstName": "Raz",
        "lastName": "ari",
        "email": "[e-mail]",
        "phoneNumber": "5149455541"
    },
    "employee": {
        "firstName": "Garcon",
        "lastName": "Mansur",
        "email": "[e-mail]",
        "phoneNumber": "541659898"
    },
    "address": {
        "location": "10424 rue du loili, Montreal, H9P1Z5"
    }
}

大多数时候，预订中的员工实体将是数据库中已经存在的员工，但是现在每次我发布这个JSON时，它都会在数据库中创建一个新的员工记录。

Answer 1

我建议你提供一个实体的id字段，Hibernate会自动检查和设置。如果没有，它会创建新的记录。但是如果不可能的话，就像@YoManToMero提到的那样手动检查它