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Calibracao删除EntityManager.remove(calibracao)的实例时，我收到以下错误：

[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 ])

有谁知道为什么会这样？

Answer 1

除非指定CascadeType，否则无法删除外键引用的实例。你可以做的是在ManyToOne关系的cascade属性上添加你想要的正确效果。

可能的值有：http://docs.oracle.com/javaee/6/api/javax/persistence/CascadeType.html

另外，请确保您的数据库表DDL（外键）允许删除。

Answer 2

考虑这样做：

在Calibracao实体中设置为null ParametroStatus属性。
尝试em.remove（）对那个Calibracao实体。

将引用设置为null可以解决问题，唯一的想法是当您尝试删除实体时出现的更新语句。

删除包含@ManyToOne的实体时出现JPA错误

2 个答案: