我正在使用Spring，hibernate和MySql，但是我对查询结果的分类有一些问题。 首先在我的实体中，我在Set结构（@OneToMany方面）上添加了@JsonManagedReference，在单个对象引用（@ManyToOne方面）上添加了@JsonBackReference，它可以工作，但我无法检索所有需要的信息（例如@ManyToOne引用） 。 所以我在设置结构上交换@JsonBackReference，在单个对象上交换@JsonManagedReference但我检索
No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.model.tablesField.TableUI["data"]->java.util.ArrayList[0]->com.domain.Car["carType"]->com.domain.CarType_$$_jvst744_f["handler"])
我也尝试使用@JsonIgnore设置结构，但它不适用于相同的问题。 这是我的弹簧配置
private Properties getHibernateProperties() {
Properties properties = new Properties();
properties.put(PROPERTY_NAME_HIBERNATE_DIALECT, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_DIALECT));
// properties.put(PROPERTY_NAME_HIBERNATE_SHOW_SQL, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_SHOW_SQL));
properties.put(PROPERTY_NAME_HIBERNATE_FORMAT_SQL, env.getRequiredProperty(PROPERTY_NAME_HIBERNATE_FORMAT_SQL));
properties.put("hibernate.enable_lazy_load_no_trans",true);
return properties;
这是我的几个实体之一：
/**
* Car generated by hbm2java
*/
@Entity
@Table(name = "car", catalog = "ATS")
public class Car implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer idCar;
@JsonManagedReference
private CarType carType;
@JsonManagedReference
private Fleet fleet;
private String id;
private int initialKm;
private String carChassis;
private String note;
@JsonBackReference
private Set<Acquisition> acquisitions = new HashSet<Acquisition>(0);
public Car() {
}
public Car(CarType carType, Fleet fleet, int initialKm, String carChassis) {
this.carType = carType;
this.fleet = fleet;
this.initialKm = initialKm;
this.carChassis = carChassis;
}
public Car(CarType carType, Fleet fleet, String id, int initialKm, String carChassis, String note,
Set<Acquisition> acquisitions) {
this.carType = carType;
this.fleet = fleet;
this.id = id;
this.initialKm = initialKm;
this.carChassis = carChassis;
this.note = note;
this.acquisitions = acquisitions;
}
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id_car", unique = true, nullable = false)
public Integer getIdCar() {
return this.idCar;
}
public void setIdCar(Integer idCar) {
this.idCar = idCar;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "id_carType", nullable = false)
public CarType getCarType() {
return this.carType;
}
public void setCarType(CarType carType) {
this.carType = carType;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "id_fleet", nullable = false)
public Fleet getFleet() {
return this.fleet;
}
public void setFleet(Fleet fleet) {
this.fleet = fleet;
}
@Column(name = "id", length = 5)
public String getId() {
return this.id;
}
public void setId(String id) {
this.id = id;
}
@Column(name = "initialKm", nullable = false)
public int getInitialKm() {
return this.initialKm;
}
public void setInitialKm(int initialKm) {
this.initialKm = initialKm;
}
@Column(name = "carChassis", nullable = false, length = 20)
public String getCarChassis() {
return this.carChassis;
}
public void setCarChassis(String carChassis) {
this.carChassis = carChassis;
}
@Column(name = "note", length = 100)
public String getNote() {
return this.note;
}
public void setNote(String note) {
this.note = note;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "car")
public Set<Acquisition> getAcquisitions() {
return this.acquisitions;
}
public void setAcquisitions(Set<Acquisition> acquisitions) {
this.acquisitions = acquisitions;
}
}
使用查询的一种方法：
@Override
@RequestMapping(value = { "/cars/{idFleet}"}, method = RequestMethod.GET)
public @ResponseBody TableUI getCars(@PathVariable int idFleet) {
TableUI ajaxCall=new TableUI();
try {
ajaxCall.setData(fleetAndCarService.findCarsByIdFleet(idFleet));
return ajaxCall;
} catch (QueryException e) {
ErrorResponse errorResponse= ErrorResponseBuilder.buildErrorResponse(e);
LOG.error("Threw exception in FleetAndCarControllerImpl::addCar :" + errorResponse.getStacktrace());
return ajaxCall;
}
}
查询的两个类：
public interface DefRdiRepository extends JpaRepository<DefRdi, Integer>{
//@Query("SELECT CASE WHEN COUNT(c) > 0 THEN true ELSE false END FROM DefRdi c WHERE c.parName = ?1 AND c.description= ?2")
//Boolean existsByParNameAndDescription(String parName, String description);
//Query method of spring, I put findBy and then the key of research
DefRdi findByParNameAndDescription(String parName, String description);
}
public interface CarRepository extends JpaRepository<Car, Integer>, CarRepositoryCustom {
//Query method of spring, I put findBy and then the key of research
List<Car> findByFleetIdFleet(int idFleet);
}
我的错误在哪里？我不想要Set对象，只需要单个引用。问题出在我序列化时。感谢
更新： 我在所有设置集合上使用@JSonIgnore而Eager而不是懒惰广告一切正常，但有没有办法只在我想要时检索所有信息，例如有两个不同的查询？ 所以它不起作用
@Override
@Transactional
public List<Car> findByFleetIdFleet(int idFleet) {
List<Car> carList= carRepository.findByFleetIdFleet(idFleet);
for (Car car:carList){
Hibernate.initialize(car.getCarType());
Hibernate.initialize(car.getFleet());
}
return carList;
// return carRepository.findByFleetIdFleet(idFleet);
}
答案 0 :(得分：0)
从数据库加载时，需要急切地获取所有集合，以便由Spring进行序列化。确保你急切地获取它们（例如FetchMode.JOIN）。您还可以将@JsonManagedReference从需要的字段与@JsonIgnore交换到黑名单字段，Spring会自动序列化每个没有注释的字段。
<强>更新：
将数据存储库更改为应该有效的方法，我不确定它是否可以编译，但我认为你会明白这一点：
@EntityGraph(value = "some.entity.graph", type = EntityGraph.EntityGraphType.FETCH)
@Query(
value = "SELECT c FROM Car c INNER JOIN FETCH c.acquisitions WHERE c.id = :idFleet"
)
public interface CarRepository extends JpaRepository<Car, Integer>, CarRepositoryCustom {
//Query method of spring, I put findBy and then the key of research
List<Car> findByFleetIdFleet(int idFleet);
}
有关详细信息，请查看this帖子并阅读official documentation。
解决方法：
似乎有一个workaround，但是如上所示渴望获取这些集合应该会产生积极的性能影响，因为之后不需要加载代理。此外，控制器级别也不需要打开事务。