域表获取错误“对象引用了一个未保存的瞬态实例-在刷新之前保存瞬态实例”

Question

当我开始使用JPA时，我已经看到错误“org.hibernate.transientPropertyValueException：object references an unsaved transient instance-在刷新之前保存transient instance”。我知道general上的这个错误可以通过添加cascade=CascadeType.all来解决，但在本例中，这个错误出现在域表中，这意味着，在本例中添加CascadeType没有任何意义，因为这个实体在数据库中已经有了Id。

我的代码的相关部分是（还有另一个字段、getters、setters等）：

RAC类：

@Entity
@Table(name = "RAC", schema = "SchRAC")
public class Rac {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "RacCod")
private Long idRac;

//anoter fields (...)

@OneToMany(fetch = FetchType.LAZY, mappedBy = "rac", cascade = {CascadeType.ALL})
@JsonManagedReference 
private List<RacProvidencia> racProvidencias;

Racprovidencia类：

@Entity
@Table(name = "RACPRO", schema = "SchRAC")
public class RacProvidencia implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    @Column(name = "RacProCod")
    private Long idRacProvidencia;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "RacCod")
    @JsonBackReference //coloquei para evitar a recursao infinita de JSON
    private Rac rac;

    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
    @JoinColumn(name = "ProCod")
    private Providencia providencia;

    @NotNull
    @Column(name = "RacProNum", length = 100)
    private String numero;

    @Column(name = "RacProDat")
    private Date dataProvidencia;

@Entity
@Table(name = "PRO", schema = "SchRAC")
public class Providencia {

    @Id
    @Column(name = "ProCod")
    private Integer idProvidencia;

    @Column(name = "ProDes", length = 50)
    private String descricao;

public RacProvidencia adicionarProvidenciaRac(Long codigo, @Valid RacProvidencia racProvidencia) {
    Rac rac = this.racRepository.findById(codigo).get();
    racProvidencia.setRac(rac);
    return racProvidenciaRepository.save(racProvidencia);
}

Answer 1

你有一个双向的关系，但你只设置了关系的一方。

public RacProvidencia adicionarProvidenciaRac(Long codigo, @Valid RacProvidencia racProvidencia) {
    Rac rac = this.racRepository.findById(codigo).get();
    racProvidencia.setRac(rac);

    rac.getRacProvidencias().add(racProvidencia);  // <-- This

    return racProvidenciaRepository.save(racProvidencia);
}

您的持久性提供者需要这两个方面。