本文介绍了JPA:EntityGraph和地图的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我将EclipseLink 2.6.3用作JPA提供程序.我有两个实体:
I use EclipseLink 2.6.3 as JPA provider. I have two entities:
@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
}
当我加载没有EntityGraph的ClassA实体时，一切工作正常.但是，如果我执行以下代码:
When I load ClassA entity without EntityGraph everything works well. However, if I do the following code:
String queryString="SELECT a FROM ClassA a WHERE a.uuid='dj000000001111111111a1'";
EntityGraph<ClassA> eg = em.createEntityGraph(ClassA.class);
eg.addAttributeNodes(new String[]{"uuid","comment"});
eg.addSubgraph("texts").addAttributeNodes(new String[]{"uuid","code","name"});
Query query = em.createQuery(queryString);
query.setHint("javax.persistence.fetchgraph", eg);
List<ClassA> items=query.getResultList();
em.close();
我收到以下异常:
[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)
如何解决?这是错误还是我做错了什么?
How to fix it? Is this a bug or I do something wrong?
推荐答案
免责声明-我不是EclipseLink开发人员，可能是错误的.
Disclaimer - I am not EclipseLink developer and I may be wrong.
正如我所发现的那样，问题在于Map在EntityGraph中不被视为集合.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方法:
As I found out the problem is that Map is not considered as collection in EntityGraph. So I added some code to org.eclipse.persistence.internal.sessions.AbstractSession as a temp workaround for my problem:
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);
}
}
这篇关于JPA:EntityGraph和地图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！