Java JPA:EntityGraph和map

我使用EclipseLink 2.6.3作为JPA提供者。我有两个实体：

@Entity
public class ClassA{

    @Id
    private String uuid;

    private String comment;

    @OneToMany(fetch = FetchType.EAGER,cascade = CascadeType.ALL,mappedBy = "classA",orphanRemoval = false)
    @MapKey(name="code")
    private Map<String,ClassB> texts;
    //+ getters and setters
}

@Entity
public class ClassB {

    @Id
    private String uuid;

    private String code;

    private String name;

     @ManyToOne
    @JoinColumn(name = "comeColname")
    private ClassA classA;

   //+getters and setters
}

---

如何修复它？这是一个bug还是我做错了什么？

免责声明-我不是EclipseLink开发人员，我可能是错的

我发现问题在于，在EntityGraph中，Map不被视为集合。因此，我在org.eclipse.persistence.internal.sessions.AbstractSession中添加了一些代码，作为解决问题的临时解决方法：

public void load(Object objectOrCollection, AttributeGroup group, ClassDescriptor referenceDescriptor, boolean fromFetchGroup) {
  if (objectOrCollection == null || group == null) {
       return;
   }       
   if (objectOrCollection instanceof Collection) {
       Iterator iterator = ((Collection)objectOrCollection).iterator();
       while (iterator.hasNext()) {
           load(iterator.next(), group, referenceDescriptor, fromFetchGroup);
       }
   }//MY CODE STARTS 
    else if(objectOrCollection instanceof Map){
        Map<Object, Object> map = (Map)objectOrCollection;
        Iterator<Map.Entry<Object, Object>> it = map.entrySet().iterator();
        while (it.hasNext()) {
          Map.Entry<Object, Object> entry = it.next();
          load(entry.getValue(), group, referenceDescriptor, fromFetchGroup);
        }
   }//MY CODE ENDS
   else {
       ClassDescriptor concreteDescriptor = referenceDescriptor;
       if (concreteDescriptor.hasInheritance() && !objectOrCollection.getClass().equals(concreteDescriptor.getJavaClass())){
           concreteDescriptor = concreteDescriptor.getInheritancePolicy().getDescriptor(objectOrCollection.getClass());
       }
       AttributeGroup concreteGroup = group.findGroup(concreteDescriptor);
       concreteDescriptor.getObjectBuilder().load(objectOrCollection, concreteGroup, this, fromFetchGroup);
   }

公共无效加载（对象objectOrCollection、AttributeGroup组、ClassDescriptor referenceDescriptor、boolean fromFetchGroup）{
if（objectOrCollection==null | | group==null）{
返回；
}       
if（对象或集合实例集合）{
迭代器迭代器=（（集合）objectOrCollection.Iterator（）；
while（iterator.hasNext（））{
加载（iterator.next（），group，referenceDescriptor，fromFetchGroup）；
}
}//我的代码开始了
else if（对象或集合实例映射）{
Map Map=（Map）objectOrCollection；
迭代器it=map.entrySet（）.Iterator（）；
while（it.hasNext（））{
Map.Entry=it.next（）；
加载（entry.getValue（），group，referenceDescriptor，fromFetchGroup）；
}
}//我的代码结束了
否则{
ClassDescriptor concreteDescriptor=referenceDescriptor；
if（concreteDescriptor.hasInheritation（）&&！objectOrCollection.getClass（）.equals（concreteDescriptor.getJavaClass（）））{
concreteDescriptor=concreteDescriptor.getInheritancePolicy（）.getDescriptor（objectOrCollection.getClass（））；
}
AttributeGroup concreteGroup=group.findGroup（concreteDescriptor）；
加载（objectOrCollection，concreteGroup，this，fromFetchGroup）；
}

---

}

JPA合同规定javax.persistence.Query.getResultList（）不允许抛出ClassCastException，因此您可以断定这是一个bug，应该向您的JPA提供者报告。在Hibernate 5.0.9.Final中，它似乎工作得很好。@Nicholas据我所知，Hibernate完全忽略了fetch graph。请看我的问题-在我的测试中，我从hibernate中得到了两个完全不同的查询，一个是上面的查询字符串，另一个是上面的整个代码段。实体图似乎比查询字符串优化得多。这里的问题是一样的：自2016年以来已经存在错误，尚未解决->

[EL Warning]: 2016-06-10 13:40:20.093--ServerSession(1266534280)--java.lang.ClassCastException: 
    java.util.Hashtable cannot be cast to org.eclipse.persistence.queries.FetchGroupTracker
    at org.eclipse.persistence.descriptors.FetchGroupManager.getObjectFetchGroup(FetchGroupManager.java:695)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.load(ObjectBuilder.java:778)
    at org.eclipse.persistence.internal.sessions.AbstractSession.load(AbstractSession.java:5189)
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:1192)
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:904)
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:1134)
    at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:460)
    at org.eclipse.persistence.internal.sessions.AbstractSession.internalExecuteQuery(AbstractSession.java:3271)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1857)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1839)
    at org.eclipse.persistence.internal.indirection.NoIndirectionPolicy.valueFromQuery(NoIndirectionPolicy.java:326)
    at org.eclipse.persistence.mappings.ForeignReferenceMapping.valueFromRowInternal(ForeignReferenceMapping.java:2334)
    at org.eclipse.persistence.mappings.ForeignReferenceMapping.valueFromRow(ForeignReferenceMapping.java:2178)
    at org.eclipse.persistence.mappings.ForeignReferenceMapping.readFromRowIntoObject(ForeignReferenceMapping.java:1505)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildAttributesIntoObject(ObjectBuilder.java:462)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:1005)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildWorkingCopyCloneNormally(ObjectBuilder.java:899)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObjectInUnitOfWork(ObjectBuilder.java:852)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:735)
    at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject(ObjectBuilder.java:689)
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.buildObject(ObjectLevelReadQuery.java:805)
    at org.eclipse.persistence.queries.ReadObjectQuery.registerResultInUnitOfWork(ReadObjectQuery.java:895)
    at org.eclipse.persistence.queries.ReadObjectQuery.executeObjectLevelReadQuery(ReadObjectQuery.java:562)
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery(ObjectLevelReadQuery.java:1175)
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:904)
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:1134)
    at org.eclipse.persistence.queries.ReadObjectQuery.execute(ReadObjectQuery.java:441)
    at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1222)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2896)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1857)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1839)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1804)
    at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery(QueryImpl.java:258)
    at org.eclipse.persistence.internal.jpa.QueryImpl.getResultList(QueryImpl.java:465)

public void load(Object objectOrCollection, AttributeGroup group, ClassDescriptor referenceDescriptor, boolean fromFetchGroup) {
  if (objectOrCollection == null || group == null) {
       return;
   }       
   if (objectOrCollection instanceof Collection) {
       Iterator iterator = ((Collection)objectOrCollection).iterator();
       while (iterator.hasNext()) {
           load(iterator.next(), group, referenceDescriptor, fromFetchGroup);
       }
   }//MY CODE STARTS 
    else if(objectOrCollection instanceof Map){
        Map<Object, Object> map = (Map)objectOrCollection;
        Iterator<Map.Entry<Object, Object>> it = map.entrySet().iterator();
        while (it.hasNext()) {
          Map.Entry<Object, Object> entry = it.next();
          load(entry.getValue(), group, referenceDescriptor, fromFetchGroup);
        }
   }//MY CODE ENDS
   else {
       ClassDescriptor concreteDescriptor = referenceDescriptor;
       if (concreteDescriptor.hasInheritance() && !objectOrCollection.getClass().equals(concreteDescriptor.getJavaClass())){
           concreteDescriptor = concreteDescriptor.getInheritancePolicy().getDescriptor(objectOrCollection.getClass());
       }
       AttributeGroup concreteGroup = group.findGroup(concreteDescriptor);
       concreteDescriptor.getObjectBuilder().load(objectOrCollection, concreteGroup, this, fromFetchGroup);
   }