mysql - 如何在 Java 中使用 hibernate 在 MySQL 数据库中创建连接表？

Question

我有两个名为预约和服务的实体表。一次预约可以提供多项服务。服务已经存储在数据库中。能新追加预约。添加新约会时，我们从下拉菜单中选择添加的服务。一次预约可以添加多项服务。我需要在约会表上存储新记录，并将相关的约会 ID 和服务 ID 存储在另一个连接表上。这里附上我的问题的图片。

我已经尝试了很多方法来做到这一点。下面是一种尝试。

这是预约类

@Entity
@Table(name="appointment")
public class Appointment extends AbstractPersistable<Long> implements Serializable {

    @OneToMany
    @JoinTable(name = "service_x_appointment", joinColumns = @JoinColumn(name = "appointment_id"),
            inverseJoinColumns = @JoinColumn(name = "beautyservice_id"))
    Set<BeautyService> beautyServices;

    private String type;
    private Date date;
    private String time;
    private String description;
    private int approval;

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

    //getter and setter

}

这是 BeautyService 类

@Entity
@Table(name="beauty_service")
public class BeautyService extends AbstractPersistable<Long>  {


    private String serviceName;
    private String timeDuration;
    private String amount;

    //getter and setter
}

这是约会 Controller 类代码，

@RequestMapping(value="/createAppointment",method = RequestMethod.POST)
    public String createAppointment(@RequestBody Appointment appointment){

        String response = null;
        response = appointmentService.save(appointment);
        return response;
    }

这里是预约服务类代码

public String save(Appointment appointment) {
        appoinmentRepository.save(appointment);
        return "Appointment added successfully";
    }

这是我的请求正文。

{   
    "type":"Type02",
    "date":null,
    "time":"20:56",
    "description":"Hellow World",
    "approval":0,
    "user":{
        "id":2,
        "name" : "Alex",
        "telephone" : "0774466886",
        "age":21,
        "email": null
    },

    "beautyServices" : [

        {   
            "id":1,
            "serviceName":"hair strate",
            "timeDuration" : "02 Hours",
            "amount" : 5000
        },
        {   
            "id":2,
            "serviceName":"Eye brows",
            "timeDuration" : "02 Hours",
            "amount" : 5000
        },
        {

            "id":3,
            "serviceName":"Near cutting",
            "timeDuration" : "02 Hours",
            "amount" : 5000
        }
        ]

}

为什么不记录在连接表中呢？只有约会表。

Answer 1

您可以通过多种方式进行。一个已经指定@Aritra Paul，它实际上是OneToMany 映射的Bidirectional 表示。我认为您想使用 UniDirectional 表示。在这种情况下，您不必使用 mappedBy。

只需像下面这样创建您的实体:

@Entity
@Table(name="appointment", schema="ADMIN")
public class Appointment implements Serializable {


     @OneToMany
     @JoinColumn(name = "appointment_id")
     @JoinTable(name = "service_appointment", joinColumns = @JoinColumn(name = "appointment_id"),
        inverseJoinColumns = @JoinColumn(name = "service_id"))
     Set<Service> services;
}


@Entity
public class Service {
       // Some Properties. No need to specify reference of Appointment here.

} 

如果你这样定义你的实体，你将有一个这样的连接表

+----------------+------------+------+-----+---------+-------+
| Field          | Type       | Null | Key | Default | Extra |
+----------------+------------+------+-----+---------+-------+
| appointment_id | bigint(20) | NO   | MUL | NULL    |       |
| service_id     | bigint(20) | NO   | PRI | NULL    |       |
+----------------+------------+------+-----+---------+-------+

希望这对您有所帮助!