带有映射的Jackson和Hibernate异常

Question

我对Hibernate Spring MVC有几个问题。这是我从控制器调用数据库实体的示例：

控制器

@Override
    @RequestMapping(value = { "/cars/{idFleet}"}, method = RequestMethod.GET)
    public @ResponseBody Response<List<Car>> getCars(@PathVariable int idFleet) throws QueryException{  
        return fleetAndCarService.findCarsByIdFleet(idFleet);
    }

服务

    @Override
//  @Transactional
    public Response<List<Car>> findCarsByIdFleet(int idFleet) throws QueryException {
        try{
            return new Response<List<Car>>(HttpStatus.OK.value(),databaseFleetsAndCarsServices.findCarsByIdFleet(idFleet));
        } catch (Exception e) {
            throw new QueryException(e);
        }
    }

数据库服务

@Override
    public List<Car> findCarsByIdFleet(int idFleet) {
        return carServices.findByFleetIdFleet(idFleet);
    }

带有命名查询的car服务

@Override
@Transactional
public List<Car> findByFleetIdFleet(int idFleet) {
    return carRepository.findByFleetIdFleet(idFleet);
}

汽车储存库

public interface CarRepository extends JpaRepository<Car, Integer> {

    //Query method of spring, I put findBy and then the key of research 
    List<Car> findByFleetIdFleet(int idFleet);

}

汽车实体

@Entity

@Table(name = "car "，catalog = "ATS ")公共类car实现java.io.Serializable {

/**
 * 
 */
private static final long serialVersionUID = 1L;
private Integer idCar;
private CarType carType;
private Fleet fleet;
private String id;
private int initialKm;
private String carChassis;
private String note;
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;
    }
}

车型（外键链接，一对多关系）

/**
 * CarType generated by hbm2java
 */
@Entity
@Table(name = "carType", catalog = "ATS")
public class CarType implements java.io.Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private String idCarType;
    private String note;
    private Set<Car> cars = new HashSet<Car>(0);

    public CarType() {
    }

    public CarType(String idCarType) {
        this.idCarType = idCarType;
    }

    public CarType(String idCarType, String note, Set<Car> cars) {
        this.idCarType = idCarType;
        this.note = note;
        this.cars = cars;
    }

    @Id

    @Column(name = "id_carType", unique = true, nullable = false, length = 5)
    public String getIdCarType() {
        return this.idCarType;
    }

    public void setIdCarType(String idCarType) {
        this.idCarType = idCarType;
    }

    @Column(name = "note", length = 100)
    public String getNote() {
        return this.note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "carType")
    public Set<Car> getCars() {
        return this.cars;
    }

    public void setCars(Set<Car> cars) {
        this.cars = cars;
    }

}

车队实体

@Entity
@Table(name = "fleet", catalog = "ATS")
public class Fleet implements java.io.Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Integer idFleet;
    private Ecu ecu;
    private String application;
    private String cubic;
    private int power;
    private String euroClass;
    private String engineType;
    private String traction;
    private String transmission;
    private String note;
    private Set<Car> cars = new HashSet<Car>(0);

收购实体

@Entity
@Table(name = "acquisition", catalog = "ATS")
public class Acquisition implements java.io.Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Integer idAcquisition;
    private Car car;
    private DpfWeighting dpfWeighting;
    private MissionProfile missionProfile;
    private OilSample oilSample;
    private Shift shift;
    private SwVersion swVersion;
    private Date date;
    private float sessionDuration;
    private int beginKm;
    private int endKm;
    private String driverName;
    private String dataset;
    private String drChannelsConf;
    private String excelRow;
    private Set<Rdi> rdis = new HashSet<Rdi>(0);
    private Set<SelfLearning> selfLearnings = new HashSet<SelfLearning>(0);
    private Set<Iupr> iuprs = new HashSet<Iupr>(0);

我正在使用maven和4.2.1.RELEASE 4.3.11最终版

当我调用控制器时，我收到一个异常:

com.fasterxml.jackson.databind。JsonMappingException：找不到类org.hibernate.proxy.pojo.javassist的序列化程序。JavassistLazyInitializer和未发现用于创建BeanSerializer的属性（为了避免异常，请禁用SerializationFeature.FAIL_ON_EMPTY_BEANS）（通过引用链：com.model.Response[“body”]-

我想知道我是否必须从实体中删除集合变量，以及如何解决映射中的异常。感谢我在每个实体上使用@ JsonIgnoreProperties({ " hibernateLazyInitializer "，" handler"})，但它是正确的吗？此外，我对实体查询进行了循环(hibernate工具写所有实体有可能出错，或者我选择了错误的方式来生成实体？)

当我使用存储库方法时，例如

@Override
@Transactional
public List<Fleet> getFleets() {
    return fleetRepository.findAll();
}

没问题，很好用

更新：我在@OneToMore变量上添加了@JsonManagedIndex，在@ManyToOne变量上添加了@JsonBackReference，它似乎可以工作，但现在在汽车上，我只能看到Acquiption，而不是Fleet和CarType（所以有JsonBackReference的注释），而不是查询，我收到了所有对象，但carType和Fleet为空，我需要相反的，所以我需要车队和carType，而不是收购。这是我找到它的链接，带有Jackson JSON和Hibernate JPA问题的无限递归

Answer 1

尝试将@ManyToOne（fetch=FetchType.EAGER）添加到您的汽车entity-attribute（或method） Car实体应具有实体对象而不是代理对象。

从应用程序返回实体不是好的做法，因为您无法控制将返回哪些关系和数据。相反，您应该返回VO（值对象）。使用VO是安全的，您可以控制从应用程序返回的内容。对于从实体到VO对象（包括关系）的映射，您可以使用一些映射器，例如Orika。