Question

我在hibernate项目上工作，在Car和CarDriver之间有@ManyToMany关系。问题是这种关系也有属性，因此我使用了一个连接到Car和CarDriver的独立实体，这个实体叫做CarUsage。

我的问题是，当我坚持使用CarUsage对象时，Car和CarDriver中的CarUsage列表并没有填充这个新对象。

这是我的实体：

汽车：

@Entity
@Table(name = "car")
@Inheritance(strategy = InheritanceType.JOINED)
public class Car extends BaseEntity {

@Column(name = "registration_plate")
private String registrationPlate;

@OneToMany(mappedBy="car")
private List<CarUsage> carUsages;

public String getRegistrationPlate() {
    return registrationPlate;
}

public void setRegistrationPlate(String registrationPlate) {
    this.registrationPlate = registrationPlate;
}

public List<CarUsage> getCarUsages() {
    return carUsages;
}

public void setCarUsages(List<CarUsage> carUsages) {
    this.carUsages = carUsages;
}
}

CarDriver

@Entity
@Table(name="car_driver")
public class CarDriver extends BaseEntity {

@OneToMany(mappedBy="carDriver")
private List<CarUsage> carUsages;

public List<CarUsage> getCarUsages() {
    return carUsages;
}

public void setCarUsages(List<CarUsage> carUsages) {
    this.carUsages = carUsages;
}
}

我的JoinTable CarUsage：

@Entity
@Table(name = "car_usage")
public class CarUsage extends BaseEntity {

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "car_id")
private Car car;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "car_driver_id")
private CarDriver carDriver;
@Column(name = "start_date")
private Date startDate;
@Column(name = "end_date")
private Date endDate;
@Column(name = "active", nullable = false)
private boolean active;

public Car getCar() {
    return car;
}

public void setCar(Car car) {
    this.car = car;
}

public CarDriver getCarDriver() {
    return carDriver;
}

public void setCarDriver(CarDriver carDriver) {
    this.carDriver = carDriver;
}

public Date getStartDate() {
    return startDate;
}

public void setStartDate(Date startDate) {
    this.startDate = startDate;
}

public Date getEndDate() {
    return endDate;
}

public void setEndDate(Date endDate) {
    this.endDate = endDate;
}

public boolean isActive() {
    return active;
}

public void setActive(boolean active) {
    this.active = active;
}
}

当我坚持使用新的CarUsage时，Car和CarDriver中的列表不会更新。

CarUsage carUsage = carUsageCreator.makeCarUsage(companyCar, carDriver, new Date(), new Date(), true);
    carUsageDao.persist(carUsage);

有谁知道我做错了什么？

Answer 1

尝试使用JPA / Hibernate Cascading：

选择关系的所有者方

汽车＆gt; CarUsage＆gt; CarDriver或CarDriver＆gt; CarUsage＆gt;汽车。

如果CarDriver是所有者方，则映射应为

@OneToMany(mappedBy="carDriver",cascade = CascadeType.ALL, orphanRemoval = true)
private List<CarUsage> carUsages;

要创建新的carUsage关系，您可以创建如下方法：

public void driveCar(CarDriver carDriver, Car car){
    CarUsage carUsage = new CarUsage(carDriver, car, Date()....)
    carDriver.getCarUsages().add(carUsage);
    car.getCarUsages().add(carUsage);// Just to maintain coherence for the rest of the current transaction
      ...
}

如果您在交易中，此代码将自动保留carUsage实例。（不再需要carUsageDao.persist（carUsage））..

为什么在持久化JoinTable对象时我的OneToMany列表没有填充？

1 个答案: