java - 删除包含 @ManyToOne 的实体时出现 JPA 错误

Question

所以我正在使用以下两个类:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING, length = 1)
@Table(name = "calibracao", catalog = "aquitel", schema = "")
@XmlRootElement
public abstract class Calibracao implements Serializable {    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "idCalibracao")
    private Long idCalibracao;

    @Basic(optional = false)
    @Column(name = "type")
    private String type;

    @Basic(optional = false)
    @Column(name = "adc")
    private int adc;

    @Basic(optional = false)
    @Column(name = "voltagem")
    private float voltagem;

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "calibracao")
    private CalibracaoPoco calibracaoPoco;

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "calibracao")
    private CalibracaoRepetidor calibracaoRepetidor;

    @JoinColumn(name = "parametroStatus", referencedColumnName = "idParametro_Status")
    @ManyToOne(optional = false)
    private ParametroStatus parametroStatus;

    //Getters and setters        

}

和

@Entity
@Table(name = "parametro_status", catalog = "aquitel", schema = "")
@XmlRootElement
public class ParametroStatus implements Serializable {        
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "idParametro_Status")
    private Integer idParametroStatus;

    @Basic(optional = false)
    @Column(name = "nome")
    private String nome;

    @Column(name = "unidadeMedida")
    private String unidadeMedida;    

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "parametro")
    private List<Status> statusList;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "parametroStatus")
    private List<Calibracao> calibracaoList;    

    //Getters and setters

}

使用以下代码实例化实体对象:

public class AdcCalibratior extends javax.swing.JFrame {

    List<Calibracao> points;

    public AdcCalibrator(){
        //Unrelated code ...
        points = getCalibration(selectedNode, selectedParameter);
    }

    //Unrelated code ...

    private List<Calibracao> getCalibration(Object node, ParametroStatus parameter) {
        if (node instanceof Poco) {
            TypedQuery query = em.createNamedQuery("CalibracaoPoco.findByParametro", CalibracaoPoco.class);
            query.setParameter("poco", (Poco) node);
            query.setParameter("parametro", parameter);
            return query.getResultList();
        } else {
            TypedQuery query = em.createNamedQuery("CalibracaoRepetidor.findByParametro", CalibracaoRepetidor.class);
            query.setParameter("repetidor", (Repetidor) node);
            query.setParameter("parametro", parameter);
            return query.getResultList();
        }
    }

//More unrelated code ...

}

当我尝试使用 EntityManager.remove(calibracao) 删除 Calibraao 实例时，出现以下错误:

[EL Warning]: 2014-02-15 22:49:43.27--UnitOfWork(2118956727)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'parametroStatus' cannot be null
Error Code: 1048
Call: UPDATE aquitel.calibracao SET parametroStatus = ? WHERE (idCalibracao = ?)
        bind => [2 parameters bound]
Query: DeleteObjectQuery(unesp.lebac.aquitel.dataLink.enitity.CalibracaoPoco[ idCalibracao=6 ])

有谁知道为什么会发生这种情况吗？

Answer 1

考虑这样做:

1. 在 Calibracao 实体中将 ParametroStatus 属性设置为 null。
2. 尝试对 Calibracao 实体执行 em.remove() 操作。

将引用设置为 null 可以解决问题，唯一觉得奇怪的是当您尝试删除实体时出现的更新语句。