休眠中的一对多双映射

Question

我想使用一对多关系映射 2 个实体。

这两个实体是机场和flight_schedule。

一个机场可以有多个航班时刻表。

但是，一个航班时刻表可以有 2 个机场。出发机场和到达机场都是他们。

所以，我想使它们成为一对多关联两次。

我的意思是，机场和 flight_schedule 有两次相同的关系。

希望您能理解这种情况。

所以，我所做的是：

Airport.java

@Entity
@Table
public class Airport implements java.io.Serializable {

private Integer airportId;
private String name;
private String country;
private String city;
private Set<String> gateway = new HashSet<String>(0);
private Set<FlightSchedule> depFlightSchedule = new HashSet<FlightSchedule>(0);
private Set<FlightSchedule> arrFlightSchedule = new HashSet<FlightSchedule>(0);

public Airport() {
}

public Airport(String name, String country, String city) {
    this.name = name;
    this.country = country;
    this.city = city;
}

public Airport(String name, String country, String city, Set<String> gateway, Set<FlightSchedule> depFlightSchedule, Set<FlightSchedule> arrFlightSchedule) {
    this.name = name;
    this.country = country;
    this.city = city;
    this.gateway = gateway;
    this.depFlightSchedule = depFlightSchedule;
    this.arrFlightSchedule = arrFlightSchedule;
}

@Id
@GeneratedValue(strategy = IDENTITY)

@Column(name = "airport_id", unique = true, nullable = false)
public Integer getAirportId() {
    return this.airportId;
}

.... getters and setters .... 

@ElementCollection
@JoinTable(name = "gateway", joinColumns = @JoinColumn(name = "airport_id"))
@Column(name = "gateway_no") 
public Set<String> getGateway() {
    return this.gateway;
}

public void SetGateway(Set<String> gateway) {
    this.gateway = gateway;
}


@OneToMany(fetch = FetchType.LAZY, mappedBy = "depAirport")
public Set<FlightSchedule> getDepFlightSchedule() {
    return this.depFlightSchedule;
}

public void setDepFlightSchedule(Set<FlightSchedule> depFlightSchedule) {
    this.depFlightSchedule = depFlightSchedule;
}


@OneToMany(fetch = FetchType.LAZY, mappedBy = "arrAirport")
public Set<FlightSchedule> getArrFlightSchedule() {
    return this.arrFlightSchedule;
}

public void setArrFlightSchedule(Set<FlightSchedule> arrFlightSchedule) {
    this.arrFlightSchedule = arrFlightSchedule;
}

}

最后两个'@OneToMany'是机场和flight_schedule之间的关系。

此外，下面是FlightSchedule.java

@Entity
@Table
public class FlightSchedule implements java.io.Serializable {

private Integer flightscheduleId;
private Date depDay;
private Date depTime;
private Date arrDay;
private Date arrTime;
private Double flightTime;
private Set<BoardingPass> boardingPasses = new HashSet<BoardingPass>(0);
private Airplane airplane;
private Airport depAirport;
private Airport arrAirport;

public FlightSchedule() {
}

public FlightSchedule(Date depDay, Date depTime, Date arrDay, Date arrTime) {
    this.depDay = depDay;
    this.depTime = depTime;
    this.arrDay = arrDay;
    this.arrTime = arrTime;
}

public FlightSchedule(Date depDay, Date depTime, Date arrDay, Date arrTime, Double flightTime) {
    this.depDay = depDay;
    this.depTime = depTime;
    this.arrDay = arrDay;
    this.arrTime = arrTime;
    this.flightTime = flightTime;
}

public FlightSchedule(Date depDay, Date depTime, Date arrDay, Date arrTime, Double flightTime, 
        Set<BoardingPass> boardingPasses, Airplane airplane, Airport depAirport, Airport arrAirport) {
    this.depDay = depDay;
    this.depTime = depTime;
    this.arrDay = arrDay;
    this.arrTime = arrTime;
    this.flightTime = flightTime;
    this.boardingPasses = boardingPasses;
    this.airplane = airplane;
    this.depAirport = depAirport;
    this.arrAirport = arrAirport;
}

@Id
@GeneratedValue(strategy = IDENTITY)

@Column(name = "id", unique = true, nullable = false)
public Integer getFlightscheduleId() {
    return this.flightscheduleId;
}

public void setFlightscheduleId(Integer flightscheduleId) {
    this.flightscheduleId = flightscheduleId;
}

....getters and setters... 

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "airport_id", nullable = false)
public Airport getDepAirport() {
    return this.depAirport;
}

public void setDepAirport (Airport depAirport) {
    this.depAirport = depAirport;
}

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "airport_id", nullable = false)
public Airport getArrAirport() {
    return this.arrAirport;
}

public void setArrAirport (Airport arrAirport) {
    this.arrAirport = arrAirport;
}

}

如上，最后两个'@ManyToOne'就是airport和flight_schedule的关系。

通过这段代码，我得到了一个错误 'MappingException'。

上面写着 RootClass(PersistentClass).checkColumnDuplication(Set, Iterator)。

我如何确定这种关系？我该如何解决这个错误？

Answer 1

你说一个航班时刻表有两个不同的机场：

But, one flight schedule can have 2 airports. departure airport, and arrived airport are them.

但是，您试图将 depAirport 和 arrAirport 映射到同一列 airport_id。您应该针对 table 中的外键列分别更改它，例如 @JoinColumn(name="dep_airport_id") 和 @JoinColumn(name="arr_airport_id")。

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