有人可以解释在JPA和Hibernate中映射的吗?
2022-08-31 06:06:08
						我是休眠的新手,需要使用一对多和多对一的关系。在我的对象中,这是一种双向关系,因此我可以从任何一个方向遍历。 是推荐的方式,但是,我无法理解它。有人可以解释一下:mappedBy
- 推荐的用法是什么?
 - 它解决了什么目的?
 
为了我的例子,这是我的带有注释的类:
- 
Airline拥有许多AirlineFlights - 
许多属于一个
AirlineFlightsAirline 
航空公司:
@Entity 
@Table(name="Airline")
public class Airline {
    private Integer idAirline;
    private String name;
    private String code;
    private String aliasName;
    private Set<AirlineFlight> airlineFlights = new HashSet<AirlineFlight>(0);
    public Airline(){}
    public Airline(String name, String code, String aliasName, Set<AirlineFlight> flights) {
        setName(name);
        setCode(code);
        setAliasName(aliasName);
        setAirlineFlights(flights);
    }
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="IDAIRLINE", nullable=false)
    public Integer getIdAirline() {
        return idAirline;
    }
    private void setIdAirline(Integer idAirline) {
        this.idAirline = idAirline;
    }
    @Column(name="NAME", nullable=false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = DAOUtil.convertToDBString(name);
    }
    @Column(name="CODE", nullable=false, length=3)
    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = DAOUtil.convertToDBString(code);
    }
    @Column(name="ALIAS", nullable=true)
    public String getAliasName() {
        return aliasName;
    }
    public void setAliasName(String aliasName) {
        if(aliasName != null)
            this.aliasName = DAOUtil.convertToDBString(aliasName);
    }
    @OneToMany(fetch=FetchType.LAZY, cascade = {CascadeType.ALL})
    @JoinColumn(name="IDAIRLINE")
    public Set<AirlineFlight> getAirlineFlights() {
        return airlineFlights;
    }
    public void setAirlineFlights(Set<AirlineFlight> flights) {
        this.airlineFlights = flights;
    }
}
航空公司航班:
@Entity
@Table(name="AirlineFlight")
public class AirlineFlight {
    private Integer idAirlineFlight;
    private Airline airline;
    private String flightNumber;
    public AirlineFlight(){}
    public AirlineFlight(Airline airline, String flightNumber) {
        setAirline(airline);
        setFlightNumber(flightNumber);
    }
    @Id
    @GeneratedValue(generator="identity")
    @GenericGenerator(name="identity", strategy="identity")
    @Column(name="IDAIRLINEFLIGHT", nullable=false)
    public Integer getIdAirlineFlight() {
        return idAirlineFlight;
    }
    private void setIdAirlineFlight(Integer idAirlineFlight) {
        this.idAirlineFlight = idAirlineFlight;
    }
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="IDAIRLINE", nullable=false)
    public Airline getAirline() {
        return airline;
    }
    public void setAirline(Airline airline) {
        this.airline = airline;
    }
    @Column(name="FLIGHTNUMBER", nullable=false)
    public String getFlightNumber() {
        return flightNumber;
    }
    public void setFlightNumber(String flightNumber) {
        this.flightNumber = DAOUtil.convertToDBString(flightNumber);
    }
}
编辑:
数据库架构:
AirlineFlights将idAirline作为外国钥匙,航空公司没有idAirlineFlights。这使得,航空公司航班作为所有者/识别实体?
从理论上讲,我希望航空公司成为航空公司航班的所有者。
