The entities and mappings I'm talking about in this question can be found here :)
Here is the context:
I have a parent view-model which helps to manage some entities, and which has its own session.
From this VM, I open another view-model (with its own session too), do some changements to the entity (add and/or remove children), and when I validate the changements, I commit the session and warns the first view-model to refresh the display:
public void Validate()
{
using (var tx = Session.BeginTransaction())
{
try
{
SelectedTeam.ClearRoster();
foreach (var teamPlayer in TeamPlayers)
SelectedTeam.AddPlayer(teamPlayer);
teamsRepository.SaveOrUpdate(SelectedTeam);
tx.Commit();
}
catch (Exception ex)
{
tx.Rollback();
}
finally
{
if (tx.WasCommitted)
ServiceLocator.Current.GetInstance<Mediator>().NotifyColleagues(MediatorMessages.DisplayEntityInfos, SelectedTeam.Id);
}
}
}
Here is the faulted method of the parent VM:
public void RefreshEntitiesListAndDisplayEntityInfos(int selectedEntityId)
{
TEntity entity = entitiesRepository.Load(selectedEntityId);
Session.Refresh(entity);
//...
}
The exception is thrown at the Refresh line:
NHibernate.UnresolvableObjectException
And the message is:
No row with the given identifier exists[Emidee.CommonEntities.PlayerInTeam#3
I can open and change the entity multiple times, but it seems that the exception is thrown when I delete a children, then add another one, and finally delete another one.
After some readings on the web, it seems that's because when I refresh the entity, and because I changed the HasMany relationship (because I have deleted a player for example), NH tries to reload the deleted row.
I've tried to add a NotFound.Ignore statement on the HasMany in my mappings, I've tried to force a new query to the DB instead of a Load, but I still get this exception.
Does someone know how I could fix that?
Thanks in advance
Mike
This is a known behavior when refreshing objects with modified collections.
To force reload, change your method to do session.Evict with the entity as a parameter. This is the code we use in our base model class:
public T ReGet<T>(T entity) where T : IEntity
{
var id = entity.Id;
Session.Evict(entity);
return Session.Get<T>(id);
}
Well, I've just spotted the problem.
To update the players list of the team, I used to clear the list, and add the new players, before updating the entity.
Now, I update the list by removing and adding only the players who have been moved by the user, and I don't have any problems at all now.
That's weird. I don't know what was wrong before, but as least that works now.
Related
I'm trying to implement custom cloning in my solution, i followed the instructions as in the documentation, and i encountered a roadblock in the form of this exception : The entity was never added to this ScoreDirector. Maybe that specific instance is not in the return values of the PlanningSolution's entity members. I know that this is not true because before the custom cloning, this exception wasn't thrown.
My planningClone method is setup like this :
#Override
public Solution planningClone() {
Solution clonedSolution = new Solution();
clonedSolution.id = id;
clonedSolution.code = code;
clonedSolution.score = score;
clonedSolution.field1 = field1;
clonedSolution.field2 = field2;
...............
clonedSolution.fieldN = fieldN;
List<PlanningEntity1> clonedPlanningEntity1List= new ArrayList<PlanningEntity1>(planningEntity1List.size());
List<PlanningEntity2> clonedPlanningEntity2List= new ArrayList<PlanningEntity2>(planningEntity1List.size());
for (PlanningEntity1 planningEntity: planningEntity1List) {
clonedPlanningEntity1List.add(planningEntity.clone());
}
for (PlanningEntity2 planningEntity: planningEntity2List) {
clonedPlanningEntity1List.add(planningEntity.clone());
}
clonedSolution.planningEntity1List = clonedPlanningEntity1List;
clonedSolution.planningEntity2List = clonedPlanningEntity2List;
return clonedSolution;
{
The clone method for my planning entities is implemented through the Java interface Cloneable:
protected PlanningEntity clone() {
try {
return (PlanningEntity) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return null;
}
Just to be sure, i checked every entity instance and their collections to make sure my cloning was working correctly, and it in fact is.
What step am i missing here?
If there is one planning entity pointing to another planning entity from a different class or maybe pointing to a list, than the cloning process needs to take care of the references for those planning entities so they point to the cloned objects.This is something that the default cloning process is doing without a problem, and thus leaving the solution in a consistent state. It even updates the Lists of planning entity instances in the parent planning entities correctly (covered by the method "cloneCollectionsElementIfNeeded" from the class "FieldAccessingSolutionCloner" from the OptaPlanner core).
So for example if we have the next two planning entity classes
#PlanningEntity
public class ParentPlanningEntityClass{
List<ChildPlanningEntityClass> childPlanningEntityClassList;
}
#PlanningEntity
public class ChildPlanningEntityClass{
ParentPlanningEntityClass parentPlanningEntityClass;
}
The "parentPlanningEntityClass" variable needs to be set to point to the cloned object. When it comes to the list "childPlanningEntityClassList" it first needs to be created from scratch with "new ArrayList();" so that both the working and new best solution (the one that is currently getting cloned) don't point to the same list. At the end the newly created list needs to be filled with the cloned objects.
My ASP.NET MVC 4 project is using NHibernate (behind repositories) and Castle Windsor, using the AutoTx and NHibernate Facilities. I've followed the guide written by haf and my I can create and read objects.
My PersistenceInstaller looks like this
public class PersistenceInstaller : IWindsorInstaller
{
public void Install(Castle.Windsor.IWindsorContainer container, Castle.MicroKernel.SubSystems.Configuration.IConfigurationStore store)
{
container.AddFacility<AutoTxFacility>();
container.Register(Component.For<INHibernateInstaller>().ImplementedBy<NHibernateInstaller>().LifeStyle.Singleton);
container.AddFacility<NHibernateFacility>(
f => f.DefaultLifeStyle = DefaultSessionLifeStyleOption.SessionPerWebRequest);
}
}
The NHibernateInstaller is straight from the NHib Facility Quickstart.
I am using ISessionManager in my base repository...
protected ISession Session
{
get
{
return _sessionManager.OpenSession();
}
}
public virtual T Commit(T entity)
{
Session.SaveOrUpdate(entity);
return entity;
}
Finally, my application code which is causing the problem:
[HttpPost]
[ValidateAntiForgeryToken]
[Transaction]
public ActionResult Maintain(PrescriberMaintainViewModel viewModel)
{
if (ModelState.IsValid)
{
var prescriber = UserRepository.GetPrescriber(User.Identity.Name);
//var prescriber = new Prescriber { DateJoined = DateTime.Today, Username = "Test" };
prescriber.SecurityQuestion = viewModel.SecurityQuestion;
prescriber.SecurityAnswer = viewModel.SecurityAnswer;
prescriber.EmailAddress = viewModel.Email;
prescriber.FirstName = viewModel.FirstName;
prescriber.LastName = viewModel.LastName;
prescriber.Address = new Address
{
Address1 = viewModel.AddressLine1,
Address2 = viewModel.AddressLine2,
Address3 = viewModel.AddressLine3,
Suburb = viewModel.Suburb,
State = viewModel.State,
Postcode = viewModel.Postcode,
Country = string.Empty
};
prescriber.MobileNumber = viewModel.MobileNumber;
prescriber.PhoneNumber = viewModel.PhoneNumber;
prescriber.DateOfBirth = viewModel.DateOfBirth;
prescriber.AHPRANumber = viewModel.AhpraNumber;
prescriber.ClinicName = viewModel.ClinicName;
prescriber.ClinicWebUrl = viewModel.ClinicWebUrl;
prescriber.Qualifications = viewModel.Qualifications;
prescriber.JobTitle = viewModel.JobTitle;
UserRepository.Commit(prescriber);
}
return View(viewModel);
}
The above code will save a new prescriber (tested by uncommenting out the commented out line etc).
I am using NHProf and have confirmed that no sql is sent to the database for the Update. I can see the read being performed but that's it.
It seems to me that NHibernate doesn't recognise the entity as being changed and therefore does not generate the sql. Or possibly the transaction isn't being committed?
I've been scouring the webs for a few hours now trying to work this one out and as a last act of desperation have posted on SO. Any ideas? :)
Oh and in NHProf I see three Sessions (1 for the GetPrescriber call from the repo, one I assume for the update (with no sql) - and one for some action in my actionfilter on the base class). I also get an alert about the use of implicit transactions. This confuses me because I thought I was doing everything I needed to get an transaction - using AutoTx and the Transaction attribute. I also expected there to be only 1 session per webrequest, as per my Windsor config.
UPDATE: It seems, after spending the day reading through the source for NHibernateFacility and AutoTx Facility for automatic transactions, that AutoTx is not setting the Interceptors on my implementation of INHibernateInstaller. It seems this means whenever SessionManager calls OpenSession it is calling the default version with no parameter, rather than the one that accepts an Interceptor. Internally AutoTxFacility registers TransactionInterceptor with windsor, so that it can be added the Interceptor on my INHibernateInstaller concrete, by windsor making use of the AutoTx's TransactionalComponentInspector
AutoTxFacility source on github
To me it looks like creating sessions for every call to the repository. A session should span the whole business operation. It should be opened at the beginning and committed and disposed at the end.
There are other strange things in this code.
Commit is a completely different concept than SaveOrUpdate.
And you don't need to tell NH to store changes anyway. You don't need to call session.Save for objects that are already in the session. They are stored anyway. You only need to call session.Save when you add new objects.
Make sure that you use a transaction for the whole business operation.
There is one most likely "unintended" part in the code snippet above. And proven by observation made by NHProf
Oh and in NHProf I see three Sessions (1 for the GetPrescriber call
from the repo, one I assume for the update (with no sql) - and one for
some action in my actionfilter on the base class).
Calling the OpenSession() is triggering creation of a new session instances.
protected ISession Session
{
get { return _sessionManager.OpenSession(); }
}
So, whenever the code is accessing the Session property, behind is new session instance created (again and again). One session for get, one for udpate, one for filter...
As we can see here, the session returned by SessionManager.OpenSession() must be used for the whole scope (Unit of work, web request...)
http://docs.castleproject.org/Windsor.NHibernate-Facility.ashx
The syntaxh which we need, si to create one session (when firstly accessed) and reuse it until enf of scope (then later correctly close it, commit or rollback transaction...). Anyhow, first thing right now is to change the Session property this way:
ISession _session;
protected ISession Session
{
get
{
if (_session == null)
{
_session = sessionFactory.OpenSession();
}
return _session;
}
}
After spending a full day yesterday searching through the AutoTx and NHibernate facilities on github and getting nowhere, I started a clean project in an attempt to replicate the problem. Unfortunately for the replication, everything worked! I ran Update-Package on my source and brought down new version of Castle.Transactions and I was running correctly. I did make a small adjustment to my own code. That was to remove the UserRepository.Commit line.
I did not need to modify how I opened sessions. That was taken care of by the SessionManager instance. With the update to Castle.Transactions, the Transaction attribute is being recognised and a transaction is being created (as evidenced by no more alert in NHProf).
With RavenDB, creating an IDocumentSession upon app start-up (and never closing it until the app is closed), allows me to use optimistic concurrency by doing this:
public class GenericData : DataAccessLayerBase, IGenericData
{
public void Save<T>(T objectToSave)
{
Guid eTag = (Guid)Session.Advanced.GetEtagFor(objectToSave);
Session.Store(objectToSave, eTag);
Session.SaveChanges();
}
}
If another user has changed that object, then the save will correctly fail.
But what I can't do, when using one session for the lifetime of an app, is seeing changes, made by other instances of the app (say, Joe, five cubicles away), to documents. When I do this, I don't see Joe's changes:
public class CustomVariableGroupData : DataAccessLayerBase, ICustomVariableGroupData
{
public IEnumerable<CustomVariableGroup> GetAll()
{
return Session.Query<CustomVariableGroup>();
}
}
Note: I've also tried this, but it didn't display Joe's changes either:
return Session.Query<CustomVariableGroup>().Customize(x => x.WaitForNonStaleResults());
Now, if I go the other way, and create an IDocumentSession within every method that accesses the database, then I have the opposite problem. Because I have a new session, I can see Joe's changes. Buuuuuuut... then I lose optimistic concurrency. When I create a new session before saving, this line produces an empty GUID, and therefore fails:
Guid eTag = (Guid)Session.Advanced.GetEtagFor(objectToSave);
What am I missing? If a Session shouldn't be created within each method, nor at the app level, then what is the correct scope? How can I get the benefits of optimistic concurrency and the ability to see others' changes when doing a Session.Query()?
You won't see the changes, because you use the same session. See my others replies for more details
Disclaimer: I know this can't be the long-term approach, and therefore won't be an accepted answer here. However, I simply need to get something working now, and I can refactor later. I also know some folks will be disgusted with this approach, lol, but so be it. It seems to be working. I get new data with every query (new session), and I get optimistic concurrency working as well.
The bottom line is that I went back to one session per data access method. And whenever a data access method does some type of get/load/query, I store the eTags in a static dictionary:
public IEnumerable<CustomVariableGroup> GetAll()
{
using (IDocumentSession session = Database.OpenSession())
{
IEnumerable<CustomVariableGroup> groups = session.Query<CustomVariableGroup>();
CacheEtags(groups, session);
return groups;
}
}
Then, when I'm saving data, I grab the eTag from the cache. This causes a concurrency exception if another instance has modified the data, which is what I want.
public void Save(EntityBase objectToSave)
{
if (objectToSave == null) { throw new ArgumentNullException("objectToSave"); }
Guid eTag = Guid.Empty;
if (objectToSave.Id != null)
{
eTag = RetrieveEtagFromCache(objectToSave);
}
using (IDocumentSession session = Database.OpenSession())
{
session.Advanced.UseOptimisticConcurrency = true;
session.Store(objectToSave, eTag);
session.SaveChanges();
CacheEtag(objectToSave, session); // We have a new eTag after saving.
}
}
I absolutely want to do this the right way in the long run, but I don't know what that way is yet.
Edit: I'm going to make this the accepted answer until I find a better way.
Bob, why don't you just open up a new Session every time you want to refresh your data?
It has many trade-offs to open new sessions for every request, and your solution to optimistic concurrency (managing tags within your own singleton dictionary) shows that it was never intended to be used that way.
You said you have a WPF application. Alright, open a new Session on startup. Load and query whatever you want but don't close the Session until you want to refresh your data (e.g. a list of order, customers, i don't know...). Then, when you want to refresh it (after a user clicks on a button, a timer event is fired or whatever) dispose the session and open a new one. Does that work for you?
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();
}
}
In the dbml designer I've set Update Check to Never on all properties. But i still get an exception when doing Attach: "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." This approach seems to have worked for others on here, but there must be something I've missed.
using(TheDataContext dc = new TheDataContext())
{
test = dc.Members.FirstOrDefault(m => m.fltId == 1);
}
test.Name = "test2";
using(TheDataContext dc = new TheDataContext())
{
dc.Members.Attach(test, true);
dc.SubmitChanges();
}
The error message says exactly what is going wrong: You are trying to attach an object that has been loaded from another DataContext, in your case from another instance of the DataContext. Dont dispose your DataContext (at the end of the using statement it gets disposed) before you change values and submit the changes. This should work (all in one using statement). I just saw you want to attach the object again to the members collection, but it is already in there. No need to do that, this should work just as well:
using(TheDataContext dc = new TheDataContext())
{
var test = dc.Members.FirstOrDefault(m => m.fltId == 1);
test.Name = "test2";
dc.SubmitChanges();
}
Just change the value and submit the changes.
Latest Update:
(Removed all previous 3 updates)
My previous solution (removed it again from this post), found here is dangerous. I just read this on a MSDN article:
"Only call the Attach methods on new
or deserialized entities. The only way
for an entity to be detached from its
original data context is for it to be
serialized. If you try to attach an
undetached entity to a new data
context, and that entity still has
deferred loaders from its previous
data context, LINQ to SQL will thrown
an exception. An entity with deferred
loaders from two different data
contexts could cause unwanted results
when you perform insert, update, and
delete operations on that entity. For
more information about deferred
loaders, see Deferred versus Immediate
Loading (LINQ to SQL)."
Use this instead:
// Get the object the first time by some id
using(TheDataContext dc = new TheDataContext())
{
test = dc.Members.FirstOrDefault(m => m.fltId == 1);
}
// Somewhere else in the program
test.Name = "test2";
// Again somewhere else
using(TheDataContext dc = new TheDataContext())
{
// Get the db row with the id of the 'test' object
Member modifiedMember = new Member()
{
Id = test.Id,
Name = test.Name,
Field2 = test.Field2,
Field3 = test.Field3,
Field4 = test.Field4
};
dc.Members.Attach(modifiedMember, true);
dc.SubmitChanges();
}
After having copied the object, all references are detached, and all event handlers (deferred loading from db) are not connected to the new object. Just the value fields are copied to the new object, that can now be savely attached to the members table. Additionally you do not have to query the db for a second time with this solution.
It is possible to attach entities from another datacontext.
The only thing that needs to be added to code in the first post is this:
dc.DeferredLoadingEnabled = false
But this is a drawback since deferred loading is very useful. I read somewhere on this page that another solution would be to set the Update Check on all properties to Never. This text says the same: http://complexitykills.blogspot.com/2008/03/disconnected-linq-to-sql-tips-part-1.html
But I can't get it to work even after setting the Update Check to Never.
This is a function in my Repository class which I use to update entities
protected void Attach(TEntity entity)
{
try
{
_dataContext.GetTable<TEntity>().Attach(entity);
_dataContext.Refresh(RefreshMode.KeepCurrentValues, entity);
}
catch (DuplicateKeyException ex) //Data context knows about this entity so just update values
{
_dataContext.Refresh(RefreshMode.KeepCurrentValues, entity);
}
}
Where TEntity is your DB Class and depending on you setup you might just want to do
_dataContext.Attach(entity);