我遇到了使用ManyToOne双向关系保存实体的问题，这里是：
警告：HHH000437：尝试保存一个或多个与未保存的临时实体具有非可空关联的实体。在保存这些依赖实体之前，必须将未保存的瞬态实体保存在操作中。 未保存的瞬态实体：（[com.epam.apartmentsbooking.model.City＃912]） 依赖实体：（[[com.epam.apartmentsbooking.model.Apartment＃640]]） 不可空的关联：（[com.epam.apartmentsbooking.model.Apartment.city]）
org.hibernate.TransientPropertyValueException：非null属性引用瞬态值 - 必须在当前操作之前保存瞬态实例：com.epam.apartmentsbooking.model.Apartment.city - ＆gt; com.epam.apartmentsbooking.model.City
这似乎很常见，但我无法保存引用数据库中现有城市的实体。
这是我的代码
Apartment.java：
package com.epam.apartmentsbooking.model;
import java.io.Serializable;
/**
* <p>
* Class describes the apartment entity
*/
public class Apartment implements Serializable {
private Long id;
private String name;
private String accommodationType;
private Byte numberOfGuests;
private Byte numberOfBedrooms;
private Byte numberOfBathrooms;
private Float pricePerDay;
private Float square;
private Short floor;
private String description;
private City city;
/**
* Default constructor of the class
* Should be used only when properties will be set later
*/
public Apartment() {
id = -1L;
name = "Default name";
accommodationType = null;
numberOfGuests = 0;
numberOfBedrooms = 0;
numberOfBathrooms = 0;
pricePerDay = 0F;
square = 0F;
floor = 0;
description = "Default description";
city = new City();
}
/**
* Counstructor that fully makes the object, should be used in most cases
*
* @param id ID of the apartment
* @param name Name of the apartment
* @param accommodationType Accommodation type (House, Apartment, Studio Apartment)
* @param numberOfGuests Maximum number of guests that host can place in the apartment
* @param numberOfBedrooms Number of bedrooms in the apartment
* @param numberOfBathrooms Number of bathrooms in the apartment
* @param pricePerDay Price per day for the apartment
* @param square Square of the apartment (in sq. m.)
* @param floor Floor on which apartment is located
* @param description Description of the apartment
* @param city City where apartment is located
*/
public Apartment(Long id, String name, String accommodationType, Byte numberOfGuests, //NOSONAR
Byte numberOfBedrooms, Byte numberOfBathrooms, Float pricePerDay, Float square, Short floor,
String description, City city) {
this.id = id;
this.name = name;
this.accommodationType = accommodationType;
this.numberOfGuests = numberOfGuests;
this.numberOfBedrooms = numberOfBedrooms;
this.numberOfBathrooms = numberOfBathrooms;
this.pricePerDay = pricePerDay;
this.square = square;
this.floor = floor;
this.description = description;
this.city = city;
}
/**
* @return the id of the apartment
*/
public Long getId() {
return id;
}
/**
* @param id id of the apartment to be set
*/
public void setId(Long id) {
this.id = id;
}
/**
* @return the name of the apartment
*/
public String getName() {
return name;
}
/**
* @param name the name to be set
*/
public void setName(String name) {
this.name = name;
}
/**
* @return Accommodation type of the apartment
*/
public String getAccommodationType() {
return accommodationType;
}
/**
* @param accomodationType accommodationType to be set
*/
public void setAccommodationType(String accomodationType) {
this.accommodationType = accomodationType;
}
/**
* @return the maximum number of guest that may be placed in the apartment
*/
public Byte getNumberOfGuests() {
return numberOfGuests;
}
/**
* @param numberOfGuests number of guests to be set
*/
public void setNumberOfGuests(Byte numberOfGuests) {
this.numberOfGuests = numberOfGuests;
}
/**
* @return the number of bedrooms
*/
public Byte getNumberOfBedrooms() {
return numberOfBedrooms;
}
/**
* @param numberOfBedrooms the number of bedrooms to be set
*/
public void setNumberOfBedrooms(Byte numberOfBedrooms) {
this.numberOfBedrooms = numberOfBedrooms;
}
/**
* @return the number of bathrooms
*/
public Byte getNumberOfBathrooms() {
return numberOfBathrooms;
}
/**
* @param numberOfBathrooms the number of bathrooms to be set
*/
public void setNumberOfBathrooms(Byte numberOfBathrooms) {
this.numberOfBathrooms = numberOfBathrooms;
}
/**
* @return the price of stay per day
*/
public Float getPricePerDay() {
return pricePerDay;
}
/**
* @param pricePerDay the price to be set
*/
public void setPricePerDay(Float pricePerDay) {
this.pricePerDay = pricePerDay;
}
/**
* @return the square of the apartment in square meters
*/
public Float getSquare() {
return square;
}
/**
* @param square square of the apartment to be set
*/
public void setSquare(Float square) {
this.square = square;
}
/**
* @return floor number of the apartment
*/
public Short getFloor() {
return floor;
}
/**
* @param floor number of floor to be set
*/
public void setFloor(Short floor) {
this.floor = floor;
}
/**
* @return the description of the apartment
*/
public String getDescription() {
return description;
}
/**
* @param description description to be set
*/
public void setDescription(String description) {
this.description = description;
}
/**
* @return the city of the apartment
*/
public City getCity() {
return city;
}
/**
* @param city city to be set
*/
public void setCity(City city) {
this.city = city;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Apartment apartment = (Apartment) o;
if (!id.equals(apartment.id)) return false;
if (!name.equals(apartment.name)) return false;
if (accommodationType.equals(apartment.accommodationType)) return false;
if (!numberOfGuests.equals(apartment.numberOfGuests)) return false;
if (!numberOfBedrooms.equals(apartment.numberOfBedrooms)) return false;
if (!numberOfBathrooms.equals(apartment.numberOfBathrooms)) return false;
if (!pricePerDay.equals(apartment.pricePerDay)) return false;
if (!square.equals(apartment.square)) return false;
if (!floor.equals(apartment.floor)) return false;
if (!description.equals(apartment.description)) return false;
return city.equals(apartment.city);
}
@Override
public int hashCode() {
int result = id.hashCode();
result = 31 * result + name.hashCode();
result = 31 * result + accommodationType.hashCode();
result = 31 * result + numberOfGuests.hashCode();
result = 31 * result + numberOfBedrooms.hashCode();
result = 31 * result + numberOfBathrooms.hashCode();
result = 31 * result + pricePerDay.hashCode();
result = 31 * result + square.hashCode();
result = 31 * result + floor.hashCode();
result = 31 * result + description.hashCode();
result = 31 * result + city.hashCode();
return result;
}
@Override
public String toString() {
return "Apartment{" +
"id=" + id +
", name='" + name + '\'' +
", accomodationType=" + accommodationType +
", numberOfGuests=" + numberOfGuests +
", numberOfBedrooms=" + numberOfBedrooms +
", numberOfBathrooms=" + numberOfBathrooms +
", pricePerDay=" + pricePerDay +
", square=" + square +
", floor=" + floor +
", description='" + description + '\'' +
", city=" + city +
'}';
}
}
City.java：
package com.epam.apartmentsbooking.model;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
/**
* <p>
* Class describes city entity
*/
public class City implements Serializable {
private Long id;
private String name;
private Country country;
private Set<Apartment> apartments = new HashSet<>();
/**
* Default constructor
* Preferable not to use
*/
public City() {
id = 912L;
name = "Minsk";
country = new Country();
}
/**
* Creates new city object
* Should be used in most cases
*
* @param id Id of the city
* @param name Name of the city
* @param country ISO Code of the country
*/
public City(Long id, String name, Country country) {
this.id = id;
this.name = name;
this.country = country;
}
/**
* @return the name of the city
*/
public String getName() {
return name;
}
/**
* @param name The name of the city to be set
*/
public void setName(String name) {
this.name = name;
}
/**
* @return Country object which the city is references on
*/
public Country getCountry() {
return country;
}
/**
* @param country Country object to set
*/
public void setCountry(Country country) {
this.country = country;
}
/**
* @return id of the city
*/
public Long getId() {
return id;
}
/**
* @param id id to be set
*/
public void setId(Long id) {
this.id = id;
}
public Set<Apartment> getApartments() {
return apartments;
}
public void setApartments(Set<Apartment> apartments) {
this.apartments = apartments;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
City city = (City) o;
if (id != null ? !id.equals(city.id) : city.id != null) return false;
if (name != null ? !name.equals(city.name) : city.name != null) return false;
if (country != null ? !country.equals(city.country) : city.country != null) return false;
return apartments != null ? apartments.equals(city.apartments) : city.apartments == null;
}
@Override
public int hashCode() {
int result = id != null ? id.hashCode() : 0;
result = 31 * result + (name != null ? name.hashCode() : 0);
result = 31 * result + (country != null ? country.hashCode() : 0);
result = 31 * result + (apartments != null ? apartments.hashCode() : 0);
return result;
}
@Override
public String toString() {
return "City{" +
"id=" + id +
", name='" + name + '\'' +
", country=" + country +
", apartments=" + apartments +
'}';
}
}
ApartmentDaoImpl.java：
package com.epam.apartmentsbooking.dao.impl.hibernate;
import com.epam.apartmentsbooking.dao.ApartmentDao;
import com.epam.apartmentsbooking.model.Apartment;
import com.epam.apartmentsbooking.model.City;
import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.criterion.Restrictions;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;
import java.util.Collection;
/**
*
* Apartment DAO Implementation
*
* @see com.epam.apartmentsbooking.dao.ApartmentDao
*/
@Repository("apartmentDaoHibernate")
@Transactional
public class ApartmentDaoImpl extends GenericDaoImpl<Apartment, Long> implements ApartmentDao {
@Autowired
@Qualifier("sessionFactory")
private SessionFactory sessionFactory;
@Override
public Long create(Apartment newInstance) {
return (Long) sessionFactory.getCurrentSession().save(newInstance);
}
@Override
public Apartment getByName(String name) {
Query query = sessionFactory.getCurrentSession().createQuery("from Apartment where name=:name");
query.setParameter("name", name);
return (Apartment) query.uniqueResult();
}
@Override
public Collection<Apartment> getAll() {
return sessionFactory.getCurrentSession().createCriteria(Apartment.class).list();
}
@Override
public Collection<Apartment> filter(String name, String accommodationType, Byte numberOfGuests,
Byte numberOfBedrooms, Byte numberOfBathrooms, Float pricePerDay,
Long cityId) {
Criteria criteria = sessionFactory.getCurrentSession().createCriteria(Apartment.class);
criteria.add(Restrictions.ilike("name", name + "%"));
criteria.add(Restrictions.ilike("accommodationType", accommodationType + "%"));
criteria.add(Restrictions.ge("numberOfGuests", numberOfGuests));
criteria.add(Restrictions.ge("numberOfBedrooms", numberOfBedrooms));
criteria.add(Restrictions.ge("numberOfBathrooms", numberOfBathrooms));
criteria.add(Restrictions.le("pricePerDay", pricePerDay));
criteria.add(Restrictions.eq("city.id", cityId));
return criteria.list();
}
}
测试用例
@Test
@ExpectedDatabase("/apartments-test-create.xml")
public void testCreate() {
Apartment newApartment = new Apartment(null, "Test Apartment#4", "STUDIO", (byte) 3, (byte) 3, (byte) 3,
400F, 78F, (short) 4, "EPAM Studio #2", new City());
apartmentDao.create(newApartment);
}
答案 0 :(得分：0)
在你的Apartment类中，你必须告诉hibernate也可以将提交级联到'City'对象。您可以通过将@Cascade注释添加到City对象来执行此操作，如下所示：
@Cascade({ org.hibernate.annotations.CascadeType.ALL })
private City city;
现在当你坚持公寓的时候，这也将同时坚持城市。
或者，首先保留“城市”对象，然后使用持久化城市对象构建“公寓”对象。