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我在我的web应用程序中有几个领域模型类与他们自己有层次关系。一个例子是用于分类用户发布的分层结构类别结构。EclipseLink @MappedSuperclass和泛型
有一些常见的与这些类的层次性有关的逻辑。所以我试图将逻辑移入一个通用的@MappedSuperclass注解的超类。
喜欢的东西：
@MappedSuperclass
public abstract class HierarchicalBaseEntity<N extends HierarchicalBaseEntity<N>> extends BaseEntity {
@ManyToOne(optional=true)
@JoinColumn(name="parent")
private N parent;
private int depth;
public N getParent() { ...
public void setParent(N newParent) { ...
public boolean isRoot() { ...
public int getDepth() { ...
public boolean isDescendantOf(N ancestor) { ...
public static <N extends HierarchicalBaseEntity<N>> N getCommonAncestor(N a, N b) { ...
public static <N extends HierarchicalBaseEntity<N>> Collection<N> reduceToCommonAncestors(Collection<N> entities) { ...
}
子类，然后扩展HierarchicalBaseEntity给自己的泛型类型N：
@Entity
public class CategoryBean extends HierarchicalBaseEntity<CategoryBean> {
在Java这一切工作了相当干净。但不幸的是EclipseLink的似乎并不像一般的“父”字段：
private N parent;
它提供了以下异常：
Caused by: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.1.0.v20100614-r7608): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class net.timp.yaase.core.model.HierarchicalBaseEntity] uses a non-entity [class java.lang.String] as target entity in the relationship attribute [field parent].
at org.eclipse.persistence.exceptions.ValidationException.nonEntityTargetInRelationship(ValidationException.java:1341)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.RelationshipAccessor.getReferenceDescriptor(RelationshipAccessor.java:416)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ObjectAccessor.processOneToOneForeignKeyRelationship(ObjectAccessor.java:609)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ObjectAccessor.processOwningMappingKeys(ObjectAccessor.java:678)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ManyToOneAccessor.process(ManyToOneAccessor.java:107)
为什么抱怨非实体的字符串？
作为测试我试图消除仿制药，只是有父字段定义为：
private HierarchicalBaseEntity parent;
没有泛型，的EclipseLink给这个例外：
Caused by: Exception [EclipseLink-7250] (Eclipse Persistence Services - 2.1.0.v20100614-r7608): org.eclipse.persistence.exceptions.ValidationException
Exception Description: [class net.timp.yaase.core.model.OnymBean] uses a non-entity [class net.timp.yaase.core.model.HierarchicalBaseEntity] as target entity in the relationship attribute [field parent].
at org.eclipse.persistence.exceptions.ValidationException.nonEntityTargetInRelationship(ValidationException.java:1341)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.RelationshipAccessor.getReferenceDescriptor(RelationshipAccessor.java:416)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ObjectAccessor.processOneToOneForeignKeyRelationship(ObjectAccessor.java:609)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ObjectAccessor.processOwningMappingKeys(ObjectAccessor.java:678)
at org.eclipse.persistence.internal.jpa.metadata.accessors.mappings.ManyToOneAccessor.process(ManyToOneAccessor.java:107)
真HierarchicalBaseEntity它不是一个在任何情况下，实体是一个@MappedSuperclass ..但有没有办法用泛型或其他方式做到这一点？看起来您的@MappedSuperclass中没有引用其子类的字段。
这看起来与http://forums.sun.com/thread.jspa?threadID=5268944相似*，但相关问题已修复。你可以尝试与另一个提供商？ – 2010-08-08 22:52:24