java - JPA2 : ElementCollection of Enum combined with AttributeConverter

Question

我试图结合两个概念:

• 存储枚举，它们是实体的一对多关系(使用 @ElementCollection、@CollectionTable)
• 不是通过字符串或序号来保存枚举，而是通过唯一 ID(使用 @AttributeConverter)来保存

它们单独应该工作正常(根据文档判断)，但是当我将它们组合起来时，我在构建过程中遇到错误。

这是实体:

@Entity
@Table(name = "push_tokens")
public class PushTokenDAO implements Serializable {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long idx;

    @ElementCollection(targetClass = NotificationType.class, fetch = FetchType.EAGER)
    @Convert(converter = NotificationTypeConverter.class)
    @CollectionTable(
            name = "notificationtypes_of_tokens",
            joinColumns = @JoinColumn(name = "fk_tokenIdx")
    )
    @Column(name = "notificationType")
    private List<NotificationType> notificationTypes;

    /* ... */

}

这是枚举:

public enum NotificationType {
    NEW_TRANSFER(10),
    DELIVERY_REPORT(20),
    UPLOAD_CONFIRMATION(30),
    EXPIRY_WARNING(40);

    private final int code;

    NotificationType(int code) {
        this.code = code;
    }

    public static NotificationType parse(int code) {
        for (NotificationType t : NotificationType.values()) {
            if (t.code == code) {
                return t;
            }
        }
        throw new IllegalArgumentException("No such NotificationType");
    }

    public int getCode() {
        return code;
    }
}

转换器:

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

@Converter(autoApply = true)
public class NotificationTypeConverter implements AttributeConverter<NotificationType, Integer> {

    @Override
    public Integer convertToDatabaseColumn(NotificationType x) {
        return x.getCode();
    }

    @Override
    public NotificationType convertToEntityAttribute(Integer y) {
        return NotificationType.parse(y);
    }

}

集合表notificationtypes_of_tokens中只有两个数字列:

CREATE TABLE `notificationtypes_of_tokens` (
  `fk_tokenIdx` bigint(11) unsigned NOT NULL,
  `notificationType` int(11) unsigned NOT NULL,
  PRIMARY KEY (`fk_tokenIdx`,`notificationType`),
  KEY `fk_tokenIdx` (`fk_tokenIdx`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

问题发生在 EclipseLink 静态编织期间，这是构建过程的一部分:

Failed to execute goal de.empulse.eclipselink:staticweave-maven-plugin:1.0.0:weave (default) 
on project skp-server: Execution default of goal de.empulse.eclipselink:staticweave-maven-plugin:1.0.0:weave 
failed: Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.6.0.v20150309-bf26070):
    org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [skp-server-PU] failed.
Internal Exception: Exception [EclipseLink-7351] (Eclipse Persistence Services - 2.6.0.v20150309-bf26070):
    org.eclipse.persistence.exceptions.ValidationException
Exception Description: The converter class [com.skalio.skaliopush.db.NotificationTypeConverter] 
    specified on the mapping attribute [notificationTypes] from the class 
    [com.skalio.skaliopush.db.entity.PushTokenDAO] was not found. Please ensure the converter 
    class name is correct and exists with the persistence unit definition.

如果我没有在实体中专门引用转换器(省略@Convert)，则转换不会完成；枚举被映射到它的序数。这不是我想要的。

仅供引用:代码运行在 Java SE VM 上，而不是应用程序服务器或其他东西上。我必须在 persistence.xml 中指定每个实体类。

Answer 1

该解决方案与@ElementCollection、Enums或与@AttributeConverter的组合无关。

相反，答案就在问题 what has to be specified in persistence.xml when running on Java SE 中。 。错误消息也以这种方式暗示(“未找到转换器...”)。

在 persistence.xml 中指定转换器类后，编织工作正常，代码构建并按预期运行。总之:组合@ElementCollection、Enum和@AttributeConverter效果很好，如上面的代码所示。