Eclipselink :不支持的操作：[instantiateForUnitOfWorkValueHolder]

Question

当我试图访问实体中存在的方法中的Lazy @oneToMany关系属性时，会出现以下错误。

错误：

Caused by: Exception [EclipseLink-7097] (Eclipse Persistence Services - 2.6.3.v20160428-59c81c5): org.eclipse.persistence.exceptions.ValidationException
Exception Description: Operation not supported: [instantiateForUnitOfWorkValueHolder].
    at org.eclipse.persistence.exceptions.ValidationException.operationNotSupported(ValidationException.java:1496)
    at org.eclipse.persistence.internal.indirection.ProtectedValueHolder.instantiateForUnitOfWorkValueHolder(ProtectedValueHolder.java:61)
    at org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder.instantiateImpl(UnitOfWorkValueHolder.java:160)
    at org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder.instantiate(UnitOfWorkValueHolder.java:234)
    at org.eclipse.persistence.internal.indirection.DatabaseValueHolder.getValue(DatabaseValueHolder.java:89)
    at org.eclipse.persistence.indirection.IndirectList.buildDelegate(IndirectList.java:271)
    at org.eclipse.persistence.indirection.IndirectList.getDelegate(IndirectList.java:455)
    at org.eclipse.persistence.indirection.IndirectList$1.<init>(IndirectList.java:597)
    at org.eclipse.persistence.indirection.IndirectList.listIterator(IndirectList.java:596)
    at org.eclipse.persistence.indirection.IndirectList.iterator(IndirectList.java:555)
    at com.order.modelGroupBase.getStatus(GroupBase.java:205)

实体：

@Entity
@Table(name="GROUP")
@Customizer(GroupBaseCustomizer.class)
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@ClassExtractor(GroupClassExtractor.class)
@InstantiationCopyPolicy
@Cacheable
@Cache( alwaysRefresh=true,
refreshOnlyIfNewer=true,
expiry=300000,      
coordinationType = CacheCoordinationType.SEND_NEW_OBJECTS_WITH_CHANGES)
public class GroupBase {

@OneToMany(cascade=CascadeType.ALL, mappedBy="groupBase", targetEntity=Groups.class)
@PrivateOwned
private List groups = new ArrayList<>();

public OrderGroupStatus getStatus() {

//error is at this line when I try to iterate..
for (Iterator itr = getGroups().iterator(); itr.hasNext();) {
    Groups relationship = (Groups) itr.next();
    //some operation..

    }           


}

}

我在eclipselink论坛上看过，但是他们没有明确地解决这个问题，有些链接说它与我的应用程序中的weaving.But有关，我根本没有启用过编织，我也不打算这么做。

这段代码在没有JPA的Eclipselink 2.3.2上运行得很好。现在，我在JPA2.0和IBM 8.5.5.8中使用Eclipselink 2.6.3。

注意:我观察到，这个问题并非每次都会随机发生，而且当创建新对象时也是如此。

Answer 1

经过多次点击和跟踪，并纠正了我的延迟加载设置，我发现在其他实体中对同一个实体使用不同的fetchType会在SHARED_CACHE模式下导致这个问题。

@OneToMany(cascade=CascadeType.ALL, mappedBy="groupBase", targetEntity=Groups.class)
@PrivateOwned
private List groups = new ArrayList<>();

默认情况下，@OneToMany是延迟获取的，但是在另一个实体中，对于同一个实体“组”，我将fetchType配置为急切。

当我将两种提取类型都设置为惰性时，此错误将停止发生。