I need to write some business logic rigt before flush against all changed entities. One of the solution I've tried is IPreUpdateEventListener. But this event listener already have object denormalized to key-value. I need something before denormalization and even before flush.
So the questions is how to get list of changed (diry) entities.
My code to detect dirty entities
var dirtyObjects = new List<object>();
var sessionImpl = hsession.GetSessionImplementation();
foreach (NHibernate.Engine.EntityEntry entityEntry in sessionImpl.PersistenceContext.EntityEntries.Values)
{
var loadedState = entityEntry.LoadedState;
var o = sessionImpl.PersistenceContext.GetEntity(entityEntry.EntityKey);
var currentState = entityEntry.Persister.GetPropertyValues(o, sessionImpl.EntityMode);
if (entityEntry.Persister.FindDirty(currentState, loadedState, o, sessionImpl) != null)
{
dirtyObjects.Add(entityEntry);
}
}
You might look at the Flush event. But what are you trying to accomplish, exactly?
Well, best solution I've found is using PersistenceContext.
foreach (var entity in eventSource.PersistenceContext.EntityEntries.Keys)
{
// entity is entity to update...
}
Not sure if this is right solution, however.
Related
This question is largely based on the article NHibernate – Automatic change tracking for aggregate roots in DDD scenarios
Although the logic in the article seems sound I have yet to find an implementation solution that will cover all use cases.
The problem seems to be related to the following paragraph from the article
There is a slight problem here that we may generate several updates per transaction here, but I am not worried about that overly much, it is fairly simple to resolve (by keeping track of the entity and not updating if we already updated in the current transaction), so I’ll leave it up to you.
Following the article we simply force a version update whenever we update a related entity within the aggregate root. However in cases where both aggregate root and related entity are 'dirty' this will cause a double update on the aggregate root. This causes nhibernate to fall over as the second version update triggered by default from the dirty aggregate root expects the version to be the same as what was loaded from the db.
I've attempted to put a check into the 'PreInsertEventListener' and 'PreUpdateEventListener' checking if the aggregate root is dirty when updating a related entity. If this is the case then ignore the forced update of version.
public bool OnPreUpdate(PreUpdateEvent updateEvent)
{
var rootFinder = updateEvent.Entity as ICanFindMyAggregateRoot;
if (rootFinder == null)
return false;
if (!updateEvent.Session.IsAggregateRootDirty(rootFinder.MyRoot))
{
updateEvent.Session.Lock(rootFinder.MyRoot, LockMode.Force);
}
return false;
}
public static class SessionExtensions
{
public static bool IsAggregateRootDirty(this ISession session, IAggregateRoot entity)
{
ISessionImplementor sessionImplementation = session.GetSessionImplementation();
IPersistenceContext persistenceContext = sessionImplementation.PersistenceContext;
IEntityPersister entityPersister = sessionImplementation.GetEntityPersister(null, entity);
EntityEntry entityEntry = persistenceContext.GetEntry(entity);
if ((entityEntry == null) && (entity is INHibernateProxy))
{
INHibernateProxy proxy = entity as INHibernateProxy;
object obj = sessionImplementation.PersistenceContext.Unproxy(proxy);
entityEntry = sessionImplementation.PersistenceContext.GetEntry(obj);
}
object[] oldState = entityEntry.LoadedState;
object[] currentState = entityPersister.GetPropertyValues(entity, sessionImplementation.EntityMode);
int[] findDirty = entityEntry.Persister.FindDirty(currentState, oldState, entity, sessionImplementation);
var hasDirtyCollection = currentState.OfType<IPersistentCollection>().Any(x => x.IsDirty);
return (findDirty != null) || hasDirtyCollection;
}
}
This solution does seem to work albeit I still need to test it with few more use cases. However I feel as if this solution is a bit heavy handed and was hoping for a solution more along what was outlined in the article.
Is there a way to detect weather the version has already been updated in the same transaction or will be, or a simple way to keep track of entities within the transaction set have its version updated.
Thanks.
We have a number of cache regions set up in our nHibernate implementation. In order to avoid trouble with load balanced web servers, I want to effectively disable the caching on the pages that edit the cached data. I can write a method that clears out all my query caches, my class caches and my entity caches easily enough.
But what I really want is to clear the cache by region. sessionFactory.EvictQueries() will take a region parameter, but Evict() and EvictCollection() does not. I don't really want to throw away the whole cache here, nor do I want to maintain some sort of clumsy dictionary associating types with their cache regions. Does nHibernate have a way to ask an entity or collection what its caching settings are?
thanks
I've just done the same thing. For everyone's benefit, here is the method I constructed:
public void ClearCache(string regionName)
{
// Use your favourite IOC to get to the session factory
var sessionFactory = ObjectFactory.GetInstance<ISessionFactory>();
sessionFactory.EvictQueries(regionName);
foreach (var collectionMetaData in sessionFactory.GetAllCollectionMetadata().Values)
{
var collectionPersister = collectionMetaData as NHibernate.Persister.Collection.ICollectionPersister;
if (collectionPersister != null)
{
if ((collectionPersister.Cache != null) && (collectionPersister.Cache.RegionName == regionName))
{
sessionFactory.EvictCollection(collectionPersister.Role);
}
}
}
foreach (var classMetaData in sessionFactory.GetAllClassMetadata().Values)
{
var entityPersister = classMetaData as NHibernate.Persister.Entity.IEntityPersister;
if (entityPersister != null)
{
if ((entityPersister.Cache != null) && (entityPersister.Cache.RegionName == regionName))
{
sessionFactory.EvictEntity(entityPersister.EntityName);
}
}
}
}
OK, looks like i've answered my own question. The default interface that's returned when you pull out the nHibernate metadata doesn't provide information on caching, however if you dig around in the implementations of it, it does. A bit clumsy, but it does the job.
I am trying to find the perfect way to handle this exception and force client changes to overwrite any other changes that caused the conflict. The approach that I came up with is to wrap the call to Session.Transaction.Commit() in a loop, inside the loop I would do a try-catch block and handle each stale object individually by copying its properties, except row-version property then refreshing the object to get latest DB data then recopying original values to the refreshed object and then doing a merge. Once I loop I will commit and if any other StaleObjectStateException take place then the same applies. The loop keeps looping until all conflicts are resolved.
This method is part of a UnitOfWork class. To make it clearer I'll post my code:
// 'Client-wins' rules, any conflicts found will always cause client changes to
// overwrite anything else.
public void CommitAndRefresh() {
bool saveFailed;
do {
try {
_session.Transaction.Commit();
_session.BeginTransaction();
saveFailed = false;
} catch (StaleObjectStateException ex) {
saveFailed = true;
// Get the staled object with client changes
var staleObject = _session.Get(ex.EntityName, ex.Identifier);
// Extract the row-version property name
IClassMetadata meta = _sessionFactory.GetClassMetadata(ex.EntityName);
string rowVersionPropertyName = meta.PropertyNames[meta.VersionProperty] as string;
// Store all property values from client changes
var propertyValues = new Dictionary<string, object>();
var publicProperties = staleObject.GetType().GetProperties();
foreach (var p in publicProperties) {
if (p.Name != rowVersionPropertyName) {
propertyValues.Add(p.Name, p.GetValue(staleObject, null));
}
}
// Get latest data for staled object from the database
_session.Refresh(staleObject);
// Update the data with the original client changes except for row-version
foreach (var p in publicProperties) {
if (p.Name != rowVersionPropertyName) {
p.SetValue(staleObject, propertyValues[p.Name], null);
}
}
// Merge
_session.Merge(staleObject);
}
} while (saveFailed);
}
The above code works fine and handle concurrency with the client-wins rule. However, I was wondering if there is any built-in capabilities in NHibernate to do this for me or if there is a better way to handle this.
Thanks in advance,
What you're describing is a lack of concurrency checking. If you don't use a concurrency strategy (optimistic-lock, version or pessimistic), StaleStateObjectException will not be thrown and the update will be issued.
Okay, now I understand your use case. One important point is that the ISession should be discarded after an exception is thrown. You can use ISession.Merge to merge changes between a detached a persistent object rather than doing it yourself. Unfortunately, Merge does not cascade to child objects so you still need to walk the object graph yourself. So the implementation would look something like:
catch (StaleObjectStateException ex)
{
if (isPowerUser)
{
var newSession = GetSession();
// Merge will automatically get first
newSession.Merge(staleObject);
newSession.Flush();
}
}
Given 1000 documents with a complex data structure. for e.g. a Car class that has three properties, Make and Model and one Id property.
What is the most efficient way in C# to push these documents to raven db (preferably in a batch) without having to query the raven collection individually to find which to update and which to insert. At the moment I have to going like so. Which is totally inefficient.
note : _session is a wrapper on the IDocumentSession where Commit calls SaveChanges and Add calls Store.
private void PublishSalesToRaven(IEnumerable<Sale> sales)
{
var page = 0;
const int total = 30;
do
{
var paged = sales.Skip(page*total).Take(total);
if (!paged.Any()) return;
foreach (var sale in paged)
{
var current = sale;
var existing = _session.Query<Sale>().FirstOrDefault(s => s.Id == current.Id);
if (existing != null)
existing = current;
else
_session.Add(current);
}
_session.Commit();
page++;
} while (true);
}
Your session code doesn't seem to track with the RavenDB api (we don't have Add or Commit).
Here is how you do this in RavenDB
private void PublishSalesToRaven(IEnumerable<Sale> sales)
{
sales.ForEach(session.Store);
session.SaveChanges();
}
Your code sample doesn't work at all. The main problem is that you cannot just switch out the references and expect RavenDB to recognize that:
if (existing != null)
existing = current;
Instead you have to update each property one-by-one:
existing.Model = current.Model;
existing.Make = current.Model;
This is the way you can facilitate change-tracking in RavenDB and many other frameworks (e.g. NHibernate). If you want to avoid writing this uinteresting piece of code I recommend to use AutoMapper:
existing = Mapper.Map<Sale>(current, existing);
Another problem with your code is that you use Session.Query where you should use Session.Load. Remember: If you query for a document by its id, you will always want to use Load!
The main difference is that one uses the local cache and the other not (the same applies to the equivalent NHibernate methods).
Ok, so now I can answer your question:
If I understand you correctly you want to save a bunch of Sale-instances to your database while they should either be added if they didn't exist or updated if they existed. Right?
One way is to correct your sample code with the hints above and let it work. However that will issue one unnecessary request (Session.Load(existingId)) for each iteration. You can easily avoid that if you setup an index that selects all the Ids of all documents inside your Sales-collection. Before you then loop through your items you can load all the existing Ids.
However, I would like to know what you actually want to do. What is your domain/use-case?
This is what works for me right now. Note: The InjectFrom method comes from Omu.ValueInjecter (nuget package)
private void PublishSalesToRaven(IEnumerable<Sale> sales)
{
var ids = sales.Select(i => i.Id);
var existingSales = _ravenSession.Load<Sale>(ids);
existingSales.ForEach(s => s.InjectFrom(sales.Single(i => i.Id == s.Id)));
var existingIds = existingSales.Select(i => i.Id);
var nonExistingSales = sales.Where(i => !existingIds.Any(x => x == i.Id));
nonExistingSales.ForEach(i => _ravenSession.Store(i));
_ravenSession.SaveChanges();
}
I'm importing data that may or may not exist already in my database. I'd like NHibernate to associate any entities with the existing db one if it exists (probably just setting the primary key/id), or create a new one if it doesn't. I'm using S#arp architecture for my framework (MVC 2, NHibernate, Fluent).
I've added the [HasUniqueDomainSignature] attribute to the class, and a [DomainSignature] attribute to the properties I want to use for comparison. The only way I can think to do it (which is not an acceptable solution and may not even work) is the following (psuedo C#):
foreach (Book importedBook in importedBooks){
foreach (Author author in importedBook.Authors){
if (!author.IsValid()){ // NHibernate Validator will check DomainSignatures
author = _authorRepository.GetByExample(author); // This would be to get the db object with the same signature,
//but I don't think I could even update this as I iterate through it.
}
}
}
As you can see, this is both messy, and non-sensical. Add to that the fact that I've got a half dozen associations on the Book (subject, format, etc), and it doesn't make any sense. There's got to be an easy way to do this that I'm missing. I'm not a novice with NHibernate, but I'm definitely not an expert.
I might not be understanding the problem, but how can the data "may or may not exist in the database"? For example, if a Book has 2 Authors, how is the relationship stored at the database level if the Author doesn't exist?
It seems as if you're trying to use NHibernate to import your data (or create an entity if it doesn't exist) which doesn't seem correct.
Most database implementations support a conditional UPDATE-or-INSERT syntax. Oracle, for example, has a MERGE command. In combination with a Hibernate <sql-insert> block in your mapping you should be able to work something out. I don't know Fluent but I assume it supports this too.
Just realize I never gave an answer or approved another's answer. I ended up just writing a new SaveOrUpdate which takes a parameter to check for existing before persisting. I also added an attribute to my domain models to overwrite when saving/updating (although in retrospect it's only on updating that it'd be overwriting).
Here's the code if it can help anyone else in this dilemma:
public TEntity SaveOrUpdate<TEntity>(TEntity entity, bool checkForExistingEntity)
{
IRepository<TEntity> repository = new Repository<TEntity>();
if (checkForExistingEntity) {
if (entity is Entity) {
IEnumerable<PropertyInfo> props = (entity as Entity).GetSignatureProperties();
Dictionary<string, object> parameters =
props.ToDictionary(propertyInfo => propertyInfo.Name, propertyInfo => propertyInfo.GetValue(entity, null));
TEntity duplicateEntity = repository.FindOne(parameters);
if (duplicateEntity != null) {
// Update any properties with the OverwriteOnSaveUpdate attribute
foreach (var property in RepositoryHelper.GetUpdatableProperties(typeof(TEntity)))
{
object initialValue = property.GetValue(entity, null);
property.SetValue(duplicateEntity, initialValue, null);
}
// Fill in any blank properties on db version
foreach (var property in typeof(TEntity).GetProperties())
{
if (property.GetValue(duplicateEntity, null) == null) {
object initialValue = property.GetValue(entity, null);
property.SetValue(duplicateEntity, initialValue, null);
}
}
return duplicateEntity;
}
}
}
return SaveOrUpdate(entity);
}