原因：
在为“父”调用“DefaultRefreshEventListener.OnRefresh”时，在“父”和“子”之间发生“带连接加载”，首先加载“子”，然后再加载“父”，但此时暂时从会话中删除“父级”的那一刻，“子级”通过代理引用“父级”。尽管“parent1BeforeRefresh”和“parent1AfterRefresh”是不同的实例，但“parent1AfterRefresh”是指向“parent1BeforeRefresh”的代理。'child1BeforeRefresh' 和 'child1AfterRefresh' 中的问题更为严重，因为这些实例完全不相关，并且都在会话缓存中。
溶液 （NH-3253）：
如果NH-3253尚未被接受和修复，DefaultRefreshEventListener请自行替换：
2.1.x 版：
/// <summary>
/// Defines the default refresh event listener used by hibernate for refreshing entities
/// in response to generated refresh events.
/// </summary>
[Serializable]
public class DefaultRefreshEventListener : IRefreshEventListener
{
private static readonly ILog log = LogManager.GetLogger(typeof(DefaultRefreshEventListener));
public virtual void OnRefresh(RefreshEvent @event)
{
OnRefresh(@event, IdentityMap.Instantiate(10));
}
public virtual void OnRefresh(RefreshEvent @event, IDictionary refreshedAlready)
{
IEventSource source = @event.Session;
if (source.PersistenceContext.ReassociateIfUninitializedProxy(@event.Entity))
return;
object obj = source.PersistenceContext.UnproxyAndReassociate(@event.Entity);
if (refreshedAlready.Contains(obj))
{
log.Debug("already refreshed");
return;
}
EntityEntry e = source.PersistenceContext.GetEntry(obj);
IEntityPersister persister;
object id;
if (e == null)
{
persister = source.GetEntityPersister(null, obj); //refresh() does not pass an entityName
id = persister.GetIdentifier(obj, source.EntityMode);
if (log.IsDebugEnabled)
{
log.Debug("refreshing transient " + MessageHelper.InfoString(persister, id, source.Factory));
}
EntityKey key = new EntityKey(id, persister, source.EntityMode);
if (source.PersistenceContext.GetEntry(key) != null)
{
throw new PersistentObjectException("attempted to refresh transient instance when persistent instance was already associated with the Session: " +
MessageHelper.InfoString(persister, id, source.Factory));
}
}
else
{
if (log.IsDebugEnabled)
{
log.Debug("refreshing " + MessageHelper.InfoString(e.Persister, e.Id, source.Factory));
}
if (!e.ExistsInDatabase)
{
throw new HibernateException("this instance does not yet exist as a row in the database");
}
persister = e.Persister;
id = e.Id;
}
// cascade the refresh prior to refreshing this entity
refreshedAlready[obj] = obj;
new Cascade(CascadingAction.Refresh, CascadePoint.BeforeRefresh, source).CascadeOn(persister, obj, refreshedAlready);
if (e != null)
{
EntityKey key = new EntityKey(id, persister, source.EntityMode);
source.PersistenceContext.RemoveEntity(key);
if (persister.HasCollections)
new EvictVisitor(source).Process(obj, persister);
}
if (persister.HasCache)
{
CacheKey ck = new CacheKey(id, persister.IdentifierType, persister.RootEntityName, source.EntityMode, source.Factory);
persister.Cache.Remove(ck);
}
EvictCachedCollections(persister, id, source.Factory);
// NH Different behavior : NH-1601
// At this point the entity need the real refresh, all elementes of collections are Refreshed,
// the collection state was evicted, but the PersistentCollection (in the entity state)
// is associated with a possible previous session.
new WrapVisitor(source).Process(obj, persister);
// NH-3253: Forcing simple load to prevent the redundante instance
//on session:
//Ocurre when:
// -there is a 'one-to-many' 'Parent-Child' relationship;
// -AND the 'Parent' 'many-to-one' association is ' fetch="select" ';
// -AND 'Child' is using a 'composite-id' and 'key-many-to-one' to the
//'Parent'.
object result;
if (this.IsReferencedByCompositeId(persister))
result = persister.Load(id, obj, @event.LockMode, source);
string previousFetchProfile = source.FetchProfile;
source.FetchProfile = "refresh";
result = persister.Load(id, obj, @event.LockMode, source);
source.FetchProfile = previousFetchProfile;
// NH Different behavior : we are ignoring transient entities without throw any kind of exception
// because a transient entity is "self refreshed"
if (!ForeignKeys.IsTransient(persister.EntityName, obj, result == null, @event.Session))
UnresolvableObjectException.ThrowIfNull(result, id, persister.EntityName);
}
private Dictionary<EntityMetamodel, bool> IsReferencedByCompositeIdCache = new Dictionary<EntityMetamodel, bool>();
/// <summary>
/// Returns <c>true</c> if the entity in <paramref name="persister"/>
/// ('root') has a direct or indirect association with another
/// entity that is associated back to 'root' through a 'composit-id' and
/// 'key-many-to-one'.
/// </summary>
/// <param name="persister"></param>
/// <returns></returns>
private bool IsReferencedByCompositeId(IEntityPersister persister)
{
try
{
bool result = false;
if (IsReferencedByCompositeIdCache.ContainsKey(persister.EntityMetamodel))
{
result = this.IsReferencedByCompositeIdCache[persister.EntityMetamodel];
}
else
{
EntityMetamodel em =
this.GetReferrerByCompositeId(
persister.EntityMetamodel,
persister.EntityMetamodel,
false,
new Iesi.Collections.Generic.HashedSet<EntityMetamodel>());
if (em == null)
result = false;
else
result = true;
lock (this)
{
this.IsReferencedByCompositeIdCache[persister.EntityMetamodel] = result;
}
}
return result;
}
catch (Exception ex)
{
log.Error("Unespected ERROR!", ex);
throw;
}
}
/// <summary>
/// Recursive Helper for <see cref="IsReferencedByCompositeId(IEntityPersister)"/>.
/// </summary>
/// <param name="rootEM"></param>
/// <param name="nestedEM"></param>
/// <param name="neestedIsCompositeId"></param>
/// <param name="visitedList"></param>
/// <returns></returns>
private EntityMetamodel GetReferrerByCompositeId(
EntityMetamodel rootEM,
EntityMetamodel nestedEM,
bool neestedIsCompositeId,
ICollection<EntityMetamodel> visitedList)
{
EntityMetamodel emResult = null;
if (visitedList.Contains(nestedEM))
{
return emResult;
}
else
{
visitedList.Add(nestedEM);
ISessionFactoryImplementor sessionImplementor = rootEM.SessionFactory;
if (nestedEM.IdentifierProperty.Type is IAbstractComponentType)
{
IAbstractComponentType componentType = (IAbstractComponentType)nestedEM.IdentifierProperty.Type;
for (int i = 0; i < componentType.Subtypes.Length; i++)
{
IType subType = componentType.Subtypes[i];
if (!subType.IsAnyType
&& subType.IsAssociationType
&& subType is IAssociationType)
{
IAssociationType associationType = (IAssociationType)subType;
string associatedEntityName = null;
try
{
//for 'Collection Types', sometimes 'Element Type' is not an 'Entity Type'
associatedEntityName = associationType.GetAssociatedEntityName(sessionImplementor);
}
catch (MappingException me)
{
//I think it will never happen because a
//"Composit Id" can not have a property that
//uses 'NHibernate.Type.CollectionType'.
//But just in case ...
if (log.IsDebugEnabled)
log.Debug("Can not perform 'GetAssociatedEntityName'. " +
"Considering it is not an entity type: '" +
nestedEM.IdentifierProperty.Name + "." +
componentType.PropertyNames[i] + "'"
, me);
}
if (associatedEntityName != null)
{
IEntityPersister persisterNextNested = sessionImplementor.GetEntityPersister(associatedEntityName);
if (rootEM == persisterNextNested.EntityMetamodel)
{
emResult = nestedEM;
return emResult;
}
else
{
emResult = this.GetReferrerByCompositeId(
rootEM,
persisterNextNested.EntityMetamodel,
true,
visitedList);
if (emResult != null)
return emResult;
}
}
}
}
}
for (int i = 0; i < nestedEM.Properties.Length; i++)
{
StandardProperty property = nestedEM.Properties[i];
if (!property.Type.IsAnyType
&& property.Type.IsAssociationType
&& property.Type is IAssociationType)
{
IAssociationType associationType = (IAssociationType)property.Type;
string associatedEntityName = null;
try
{
//for 'Collection Types', sometimes 'Element Type' is not an 'Entity Type'
associatedEntityName = associationType.GetAssociatedEntityName(sessionImplementor);
}
catch (MappingException me)
{
if (log.IsDebugEnabled)
log.Debug("Can not perform 'GetAssociatedEntityName'. " +
"Considering it is not an entity type: '" +
nestedEM.EntityType.Name + "." +
nestedEM.PropertyNames[i] + "'",
me);
}
if (associatedEntityName != null)
{
IEntityPersister persisterNextNested = sessionImplementor.GetEntityPersister(associatedEntityName);
emResult = this.GetReferrerByCompositeId(
rootEM,
persisterNextNested.EntityMetamodel,
false,
visitedList);
if (emResult != null)
return emResult;
}
}
}
}
return null;
}
// Evict collections from the factory-level cache
private void EvictCachedCollections(IEntityPersister persister, object id, ISessionFactoryImplementor factory)
{
EvictCachedCollections(persister.PropertyTypes, id, factory);
}
private void EvictCachedCollections(IType[] types, object id, ISessionFactoryImplementor factory)
{
for (int i = 0; i < types.Length; i++)
{
if (types[i].IsCollectionType)
{
factory.EvictCollection(((CollectionType)types[i]).Role, id);
}
else if (types[i].IsComponentType)
{
IAbstractComponentType actype = (IAbstractComponentType)types[i];
EvictCachedCollections(actype.Subtypes, id, factory);
}
}
}
}
3.3.x 版：
/// <summary>
/// Defines the default refresh event listener used by hibernate for refreshing entities
/// in response to generated refresh events.
/// </summary>
[Serializable]
public class DefaultRefreshEventListener : IRefreshEventListener
{
private static readonly IInternalLogger log = LoggerProvider.LoggerFor(typeof(DefaultRefreshEventListener));
public virtual void OnRefresh(RefreshEvent @event)
{
OnRefresh(@event, IdentityMap.Instantiate(10));
}
public virtual void OnRefresh(RefreshEvent @event, IDictionary refreshedAlready)
{
IEventSource source = @event.Session;
bool isTransient = !source.Contains(@event.Entity);
if (source.PersistenceContext.ReassociateIfUninitializedProxy(@event.Entity))
{
if (isTransient)
source.SetReadOnly(@event.Entity, source.DefaultReadOnly);
return;
}
object obj = source.PersistenceContext.UnproxyAndReassociate(@event.Entity);
if (refreshedAlready.Contains(obj))
{
log.Debug("already refreshed");
return;
}
EntityEntry e = source.PersistenceContext.GetEntry(obj);
IEntityPersister persister;
object id;
if (e == null)
{
persister = source.GetEntityPersister(null, obj); //refresh() does not pass an entityName
id = persister.GetIdentifier(obj, source.EntityMode);
if (log.IsDebugEnabled)
{
log.Debug("refreshing transient " + MessageHelper.InfoString(persister, id, source.Factory));
}
EntityKey key = new EntityKey(id, persister, source.EntityMode);
if (source.PersistenceContext.GetEntry(key) != null)
{
throw new PersistentObjectException("attempted to refresh transient instance when persistent instance was already associated with the Session: " +
MessageHelper.InfoString(persister, id, source.Factory));
}
}
else
{
if (log.IsDebugEnabled)
{
log.Debug("refreshing " + MessageHelper.InfoString(e.Persister, e.Id, source.Factory));
}
if (!e.ExistsInDatabase)
{
throw new HibernateException("this instance does not yet exist as a row in the database");
}
persister = e.Persister;
id = e.Id;
}
// cascade the refresh prior to refreshing this entity
refreshedAlready[obj] = obj;
new Cascade(CascadingAction.Refresh, CascadePoint.BeforeRefresh, source).CascadeOn(persister, obj, refreshedAlready);
if (e != null)
{
EntityKey key = new EntityKey(id, persister, source.EntityMode);
source.PersistenceContext.RemoveEntity(key);
if (persister.HasCollections)
new EvictVisitor(source).Process(obj, persister);
}
if (persister.HasCache)
{
CacheKey ck = new CacheKey(id, persister.IdentifierType, persister.RootEntityName, source.EntityMode, source.Factory);
persister.Cache.Remove(ck);
}
EvictCachedCollections(persister, id, source.Factory);
// NH Different behavior : NH-1601
// At this point the entity need the real refresh, all elementes of collections are Refreshed,
// the collection state was evicted, but the PersistentCollection (in the entity state)
// is associated with a possible previous session.
new WrapVisitor(source).Process(obj, persister);
// NH-3253: Forcing simple load to prevent the redundante instance
//on session:
//Ocurre when:
// -there is a 'one-to-many' 'Parent-Child' relationship;
// -AND the 'Parent' 'many-to-one' association is ' fetch="select" ';
// -AND 'Child' is using a 'composite-id' and 'key-many-to-one' to the
//'Parent'.
object result;
if (this.IsReferencedByCompositeId(persister))
result = persister.Load(id, obj, @event.LockMode, source);
string previousFetchProfile = source.FetchProfile;
source.FetchProfile = "refresh";
result = persister.Load(id, obj, @event.LockMode, source);
if (result != null)
if (!persister.IsMutable)
source.SetReadOnly(result, true);
else
source.SetReadOnly(result, (e == null ? source.DefaultReadOnly : e.IsReadOnly));
source.FetchProfile = previousFetchProfile;
// NH Different behavior : we are ignoring transient entities without throw any kind of exception
// because a transient entity is "self refreshed"
if (!ForeignKeys.IsTransient(persister.EntityName, obj, result == null, @event.Session))
UnresolvableObjectException.ThrowIfNull(result, id, persister.EntityName);
}
private Dictionary<EntityMetamodel, bool> IsReferencedByCompositeIdCache = new Dictionary<EntityMetamodel, bool>();
/// <summary>
/// Returns <c>true</c> if the entity in <paramref name="persister"/>
/// ('root') has a direct or indirect association with another
/// entity that is associated back to 'root' through a 'composit-id' and
/// 'key-many-to-one'.
/// </summary>
/// <param name="persister"></param>
/// <returns></returns>
private bool IsReferencedByCompositeId(IEntityPersister persister)
{
try
{
bool result = false;
if (IsReferencedByCompositeIdCache.ContainsKey(persister.EntityMetamodel))
{
result = this.IsReferencedByCompositeIdCache[persister.EntityMetamodel];
}
else
{
EntityMetamodel em =
this.GetReferrerByCompositeId(
persister.EntityMetamodel,
persister.EntityMetamodel,
false,
new Iesi.Collections.Generic.HashedSet<EntityMetamodel>());
if (em == null)
result = false;
else
result = true;
lock (this)
{
this.IsReferencedByCompositeIdCache[persister.EntityMetamodel] = result;
}
}
return result;
}
catch (Exception ex)
{
log.Error("Unespected ERROR!", ex);
throw;
}
}
/// <summary>
/// Recursive Helper for <see cref="IsReferencedByCompositeId(IEntityPersister)"/>.
/// </summary>
/// <param name="rootEM"></param>
/// <param name="nestedEM"></param>
/// <param name="neestedIsCompositeId"></param>
/// <param name="visitedList"></param>
/// <returns></returns>
private EntityMetamodel GetReferrerByCompositeId(
EntityMetamodel rootEM,
EntityMetamodel nestedEM,
bool neestedIsCompositeId,
ICollection<EntityMetamodel> visitedList)
{
EntityMetamodel emResult = null;
if (visitedList.Contains(nestedEM))
{
return emResult;
}
else
{
visitedList.Add(nestedEM);
ISessionFactoryImplementor sessionImplementor = rootEM.SessionFactory;
if (nestedEM.IdentifierProperty.Type is IAbstractComponentType)
{
IAbstractComponentType componentType = (IAbstractComponentType)nestedEM.IdentifierProperty.Type;
for (int i = 0; i < componentType.Subtypes.Length; i++)
{
IType subType = componentType.Subtypes[i];
if (!subType.IsAnyType
&& subType.IsAssociationType
&& subType is IAssociationType)
{
IAssociationType associationType = (IAssociationType)subType;
string associatedEntityName = null;
try
{
//for 'Collection Types', sometimes 'Element Type' is not an 'Entity Type'
associatedEntityName = associationType.GetAssociatedEntityName(sessionImplementor);
}
catch (MappingException me)
{
//I think it will never happen because a
//"Composit Id" can not have a property that
//uses 'NHibernate.Type.CollectionType'.
//But just in case ...
if (log.IsDebugEnabled)
log.Debug("Can not perform 'GetAssociatedEntityName'. " +
"Considering it is not an entity type: '" +
nestedEM.IdentifierProperty.Name + "." +
componentType.PropertyNames[i] + "'"
, me);
}
if (associatedEntityName != null)
{
IEntityPersister persisterNextNested = sessionImplementor.GetEntityPersister(associatedEntityName);
if (rootEM == persisterNextNested.EntityMetamodel)
{
emResult = nestedEM;
return emResult;
}
else
{
emResult = this.GetReferrerByCompositeId(
rootEM,
persisterNextNested.EntityMetamodel,
true,
visitedList);
if (emResult != null)
return emResult;
}
}
}
}
}
for (int i = 0; i < nestedEM.Properties.Length; i++)
{
StandardProperty property = nestedEM.Properties[i];
if (!property.Type.IsAnyType
&& property.Type.IsAssociationType
&& property.Type is IAssociationType)
{
IAssociationType associationType = (IAssociationType)property.Type;
string associatedEntityName = null;
try
{
//for 'Collection Types', sometimes 'Element Type' is not an 'Entity Type'
associatedEntityName = associationType.GetAssociatedEntityName(sessionImplementor);
}
catch (MappingException me)
{
if (log.IsDebugEnabled)
log.Debug("Can not perform 'GetAssociatedEntityName'. " +
"Considering it is not an entity type: '" +
nestedEM.EntityType.Name + "." +
nestedEM.PropertyNames[i] + "'",
me);
}
if (associatedEntityName != null)
{
IEntityPersister persisterNextNested = sessionImplementor.GetEntityPersister(associatedEntityName);
emResult = this.GetReferrerByCompositeId(
rootEM,
persisterNextNested.EntityMetamodel,
false,
visitedList);
if (emResult != null)
return emResult;
}
}
}
}
return null;
}
// Evict collections from the factory-level cache
private void EvictCachedCollections(IEntityPersister persister, object id, ISessionFactoryImplementor factory)
{
EvictCachedCollections(persister.PropertyTypes, id, factory);
}
private void EvictCachedCollections(IType[] types, object id, ISessionFactoryImplementor factory)
{
for (int i = 0; i < types.Length; i++)
{
if (types[i].IsCollectionType)
{
factory.EvictCollection(((CollectionType)types[i]).Role, id);
}
else if (types[i].IsComponentType)
{
IAbstractComponentType actype = (IAbstractComponentType)types[i];
EvictCachedCollections(actype.Subtypes, id, factory);
}
}
}
}