Gustavo Ringel

Moving the blog

noreply@blogger.com (Gustavo Ringel) — Fri, 12 Jul 2013 11:57:00 +0000

I'm in the process of moving this blog to and to start blogging again after some busy time... It will take me a few days more to complete moving everything and start publishing there...but i'll remove this blog when I complete the work...

Problem debugging with multiple processes

noreply@blogger.com (Gustavo Ringel) — Tue, 15 Jun 2010 13:37:00 +0000

For some reasons when debugging applications using multiple threads i had an awkward behavior with Visual Studio 2008 SP1, where the debugger will skip some steps or act as I pressed F5.

After looking for a while in the web I arrived to a hotfix that solves this problem and it applies only for VS 2008 SP1.

http://support.microsoft.com/?scid=kb;en-us;957912&x=9&y=14

I hope this is useful for other people suffering the same issues.

Is NHibernate difficult or why people do not read documentation

noreply@blogger.com (Gustavo Ringel) — Sat, 13 Feb 2010 12:15:00 +0000

I found this post in google alert today

http://mattthr.blogspot.com/2010/02/quey-across-join-in-nhibernate.html

He claims this SQL is easy to write and he says that he has to work a lot with the highly “undocumented?” stupid framework called NH to make it work

SELECT * from product p
inner join sku s on s.id = p.id
WHERE p.Name like '%widget%'
OR s.SkuCode like '%wd_%'

If i write it as i write every query like this, the corresponding HQL will be something like:

SELECT p from product p
join p.SKU s
WHERE p.Name like '%widget%'
OR s.SkuCode like '%wd_%'

I mean is it easier in NH or what? And this feature is much documented…there is a trend of users trying to use criteria as the default…which i don’t think is right at all…criteria has its place and it will be overridden by a good implementation of Linq2NH but if all what you want is some translation of your SQL world to NH then you should use HQL.

Extending ICriterion to use a sql LIKE for a numeric field

noreply@blogger.com (Gustavo Ringel) — Fri, 20 Nov 2009 09:22:00 +0000

I’m almost sure it is not ANSI-SQL but, in SQL Server you can do a Like query for an int field.

Using the Like Restriction in NHibernate won’t send a like for an int field, because it is not supported for every DB. I’m migrating an application which uses like for integer fields to find domain objects which some codes starts with a known prefix.

Considering that I’m working now with SQL Server and i don’t think about migrating the app to another database i decided to extend ICriterion to get this using a StartsWith restriction

The work is very easy, basically when i create the expression i convert it in a LikeExpression, and convert the value toString, in SQL if you send a string to a like for a numeric value it will return an empty result set which for me is good enough:

public class StartsWithExpression : AbstractCriterion
    {
        private readonly ICriterion realCriterion;
        
        /// <summary>
        /// Initialize a new instance of the <see cref="EqOrNullExpression" /> class for a named
        /// Property and its value.
        /// </summary>
        /// <param name="propertyName">The name of the Property in the class.</param>
        /// <param name="value">The value for the Property.</param>
        public StartsWithExpression(string propertyName, object value)
        {
            realCriterion= new LikeExpression(propertyName, value.ToString(), MatchMode.Start);
        }

        public override string ToString()
        {
            return realCriterion.ToString();
        }

        public override TypedValue[] GetTypedValues(ICriteria criteria, ICriteriaQuery criteriaQuery)
        {
            return realCriterion.GetTypedValues(criteria, criteriaQuery);
        }

        public override IProjection[] GetProjections()
        {
            return realCriterion.GetProjections();
        }

        public override SqlString ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery,
                                              IDictionary<string, IFilter> enabledFilters)
        {
            return realCriterion.ToSqlString(criteria, criteriaQuery, enabledFilters);
        }
    }

The code is ready in the uNhAddins source.

Next thing i want to do is use this in an Example query and get the EnableLike to work with it, but currently i didn’t find out how to extend Example for this.

uNHAddins MultiSessionFactory and Conversation

noreply@blogger.com (Gustavo Ringel) — Thu, 19 Nov 2009 12:43:00 +0000

I have been asked sometimes in the Blog comments, without time to answer, how to configure the conversation to use a MultiSessionFactoryProvider instead of the regular SessionFactoryProvider we use in most of the examples.

The real place to start this is Fabio’s Blog where he talks about the SessionFactory providers.

I took the ideas from there, configured the conversation and made a simple test that has a CrudModel for an animal and a person and shows them in a ConsoleApplication.

You can find the example in the uNHAddins source

For sure it is not the best example you will see, but you can see how easily you can configure your repositories / daos to access one factory or other using uNHAddins

Asserting an event was raised

noreply@blogger.com (Gustavo Ringel) — Tue, 07 Jul 2009 06:12:00 +0000

I found the answer to this in some posts in the net. But i always forgot it and find my self looking for it again, so i will post the solution Im using here for future reference.

[Test]
public void during_single_load_getting_two_barcode_raises_event_with_them()
{
  var eventRaised = false;

dispenserProcessManager = CreateStubbedDispenserManager();

  var barcodes = new[] { "4444455555", "4444455556" };

  busterManager.Stub(bm => bm.GetSingleLoadBarcodes(Context.TelephoneType)).Return(barcodes);

dispenserProcessManager.BarcodesRead += (sender, collection) =>
{
collection.Elements.Count().Should().Be.EqualTo(2);
collection.Elements.Should().Contain(barcodes[0]);
collection.Elements.Should().Contain(barcodes[1]);
eventRaised = true;
};

dispenserProcessManager.SingleLoad();

eventRaised.Should().Be.True();
}

Inside the event i’m checking that the event was raised with the right data, and i set the eventraised variable to true. At the end i check that i really hit that line.

The Should() syntax is a handy way of asserting (at least for me) using NunitEx

Rhino Mocks Constraints for Generic List

noreply@blogger.com (Gustavo Ringel) — Fri, 29 May 2009 20:26:00 +0000

Today i was doing some tests that check that user input in a windows forms is ok and sends a notification to the user.

The notification is a list of Errors, each error has the control which has a problem and the message to show to the user, all of this to set the ErrorProvider.

Well i really want to test I’m sending the right things, but i don’t care if the error provider works fine, so i obviously decided to mock the view…

I’m not so acquainted with Rhino Mocks but find very nice the way to set the expectation for the list of errors that should be passed to the view.

view.Expect(v => v.NotifyErrors(null).Constraints(
               List.Count(Is.Equal(1)) &&
               Is.TypeOf<IEnumerable<Error>>() &&
               List.Element(0, new PropertyIs("Message", Messages.ToDateCannotBeLessThanFromDate)));

The only thing i would like to improve is the string in the PropertyIs, i maybe missing some option to do e => e.Message == Messages.ToDateCannotBeLessThanFromDate

Using KnownType for NullObject

noreply@blogger.com (Gustavo Ringel) — Fri, 22 May 2009 20:13:00 +0000

I’m a little fan of NullObject pattern. It is very handy for several use cases.

I was moving my application to WCF and defined my User as a [DataContract] and my NullUser as a [DataContract]. The login service will return a User if it exists or a NullUser if it doesn’t exist.

Well I was naively thinking it will work as is…but instead of that i got an exception it could not Serialize because NullUser was not expected as a contract…

The solution is very easy, putting the KnownType(typeof(NullUser)) as an attribute on top of the User class…then i can keep playing with my null objects.

Using the tag in NHibernate

noreply@blogger.com (Gustavo Ringel) — Sun, 26 Apr 2009 10:19:00 +0000

In NHibernate we usually use a surrogate key to represent an Id for our class. However our entities always have some natural business key like Order + OrderLine.

The problem is that there was no way to create this unique constraint for composed natural keys without using <database-object> which is not the best solution.

Since the introduction of Alpha1 we have a solution for this using the tag <natural-id> you put every property composing the Natural key inside the mapping and NH will generate the necessary unique key and nullability constraints

So if you have this mapping

<class name="Warehouse" table="Warehouses">
   <id name="Id" type="Int32">
       <generator class="hilo" />
   </id>

   <many-to-one name="ServiceCenter" column="ServiceCenterId" />
   <property name="Code" not-null="true" length="16" />

   <property name="Description" length="128" />
</class>

NH will generate:

CREATE TABLE StockManagement.dbo.Warehouses (
Id INT not null,
ServiceCenterId INT null,
Code NVARCHAR(16) not null,
Description NVARCHAR(128) null,
primary key (Id)
)

and if now you add it the <natural-id> tag

<class name="Warehouse" table="Warehouses">
   <id name="Id" type="Int32">
       <generator class="hilo" />
   </id>

   <natural-id>
       <many-to-one name="ServiceCenter" column="ServiceCenterId" />
       <property name="Code" not-null="true" length="16" />
   </natural-id>

   <property name="Description" length="128" />
</class>

you will get the DDL (i underline the addition):

CREATE TABLE StockManagement.dbo.Warehouses (
Id INT not null,
ServiceCenterId INT null,
Code NVARCHAR(16) not null,
Description NVARCHAR(128) null,
primary key (Id),
unique (ServiceCenterId, Code)
)

This way your mapping can be more self documenting. For sure it will help also for tests instead of adding manually these constraints.

Using the NHibernate Validator with a Custom Attribute

noreply@blogger.com (Gustavo Ringel) — Sat, 25 Apr 2009 19:59:00 +0000

The NHibernate Validator has an XML Configuration that covers every standard validator attribute that can be defined.

It is nice because you can change validations without changing code, etc, etc.

One question that arises several times is how to use XML when defining a new Attribute + Validator like those in the Country Specifics Validators.

The <rule> tag takes care of this. If you define a custom attribute then you give the full class name of the attribute and the parameters in the xml file like this.

<rule attribute="AttributeFullClassName">
  <param name="Value1" value="A string value"/>
  <param name="Value2" value="123"/>
  <param name ="Message" value="custom message"/>
</rule>

So you can keep using XML even for your custom validators.

format_sql property in NHibernate

noreply@blogger.com (Gustavo Ringel) — Mon, 20 Apr 2009 20:40:00 +0000

Talking with Fabio the last days I found out that the format_sql property which implementation was missing in NHibernate was added for NH Alpha3. The JIRA issue is the following:

http://nhjira.koah.net/browse/NH-1745

This means that instead of getting a loooooong line for NHibernate.Tool.hbm2ddl.SchemaExport and NHibernate.SQL queries we are getting nicest things in the log like:

INSERT
INTO
StockManagement.dbo.Locations
(Code, Id)
VALUES
(@p0, @p1);
@p0 = 1, @p1 = 32768

instead of previous:

INSERT INTO StockManagement.dbo.Locations (Code, Id) VALUES (@p0, @p1);@p0 = 1, @p1 = 32768

For sure i could have take a bigger query, but i think this is enough to show the case.

I think this is a very nice feature to have when looking for problems.

Using an external C++ DLL

noreply@blogger.com (Gustavo Ringel) — Sun, 05 Apr 2009 09:30:00 +0000

Today I had again to call a legacy DLL and again I was in trouble until I found the project where I worked on this in the past…so I decided to put me a reminder in the blog…hoping for it to be easier to find. We have a lot of dll’s for several machines written in Borland C++ and I don’t think they are going to be rewritten in something else for long.

So let’s say i need to call a method GetStatus exported by machine.dll

1) I put the dll in the path of my binaries, 2) I declare a class importing several methods like this one:

[DllImport("machine.dll", EntryPoint = "GetStatus", CallingConvention = CallingConvention.StdCall)]   
public static extern int GetStatus(StringBuilder builder);

The calling convention is dependent on the way the dll is compiled and I found that for every dll in my company StdCall is OK.

Regarding the StringBuilder it is a way to get a char* in C++ without having to take care of the \0 and other beauties…

In my case this is it because there is some abstractions there in our library i only pass a char* with an expected format and get back an integer representing the status…most of the call work this way.

So it will be easy for me to find what i need here and i hope someone finds this useful also.

uNHAddins TestUtils, Spying your log

noreply@blogger.com (Gustavo Ringel) — Sun, 22 Mar 2009 22:21:00 +0000

Not a long time ago Fabio started his uNHAddins TestUtils project…it is not finished yet, he left it a little to run for NUnitEx. But there are already some useful things there, part of it will change for sure after using it for a little while, but there are things that i think are highly stable and will be very useful.

One of them is something i always see myself copying from project to project, a LogSpy…this is something i always put in my test.commons.dll, copying from the uNHAddins or NH implementations but now it is part of uNHAddins.TestUtils, which is handy because I’m already using it.

In the uNHAddins SessionManagement Example I’m testing that I’m logging that conversation was ended after persisting the modification of an order. The idea there was testing that i can catch the event after the conversation ended, so i can publish some event, or do something…for the sake of the test i only logged and Spyed using uNHAddins syntax as shown.

[Test]
public void persisting_an_order_should_log_message()
{
  var purchaseOrder = new PurchaseOrder
 {
   Date = DateTime.Now,
   Number = "N1"
 };

 Assert.That(Spying.Logger(typeof MyConversationCreationInterceptor<>))
   .Execute(() => modifyOrderModel.Persist(purchaseOrder))
   .MessageSequence,
   Is.EqualTo(new[] { "My conversation ended" }));
}

There are some uses a bit more complex in the uNHAddins test, but that is it…in a simple way we can spay the log.

uNHAddins SessionWrapper and performance optimization

noreply@blogger.com (Gustavo Ringel) — Wed, 11 Mar 2009 20:02:00 +0000

Rub posted in Fabio’s blog and mine he was having some problems with performance using uNHAddins conversation.

I’m using the conversation for a while and i know there is no issue using it, so we asked Rub to send a test showing what he was doing to test. His test was comparing a direct call to a Dao method with a call through the Model. The time difference was being of… seconds!

The first thing i did to check what’s going on was calling again the model function after the first call…from 1 second and something we moved to…a few milliseconds…so, the problem was with something occurring in the startup.

Debugging a little, i found the problem was in the SessionWrapper with a call to a castle function CreateInterfaceProxyWithTarget. It was taking almost a second to generate the proxy to a session the first time.

For sure we should review what is happening there so we can find or ask for a solution, if possible, so Castle lovers can keep using the DynamicProxy2, but for the ones worried about the slow initialization there is a very simple solution! using the uNHAddins.LinfuAdapters.SessionWrapper instead of the uNHAddins.CastleAdapters.SessionWrapper, so the proxy is given by LinFu there…guess what…now the initialization is way faster, without changing code…

So in resume, you can keep trusting on uNHAddins conversation and you’re still invited to create tests and send to the uNHaddins forum if you find something that is suspicious in the current implementation…a better follow up of this solution can be found in the forum also.

Creating a DTO in NHibernate + HQL using PositionalToBeanResultTransformer

noreply@blogger.com (Gustavo Ringel) — Wed, 25 Feb 2009 21:55:00 +0000

The most common way to create a DTO in NHibernate (for me at least) is having a public constrctor…let’s say we have class product

public class Product
{
public virtual string Id { get; set; }
public virtual string Code { get; set; }
public virtual string Description { get; set; }
public virtual double Price { get; set; }
}

and we want to create a ProductDTO then for the classical solution we will need also a specific constructor in the ProductDTO

public class ProductDTO
{
public ProductDTO(int code, string description)
{
  Code = code
  Description = description
}
public virtual string Code { get; set; }
public virtual double Description { get; set; }
}

in the mapping class you will need to add an import of the DTO class and the named HQL something like:

<import class="NH.Domain.DTOs.ProductDTO, NH.Domain" />
... (class mapping)
<query name="GetProductDTOClassical">
  select new ProductDTO(product.Code, product.Description)
  from Product product
</query>

Finally you write the query:

var productDTO = 
  session.GetNamedQuery("GetProductDTOClassical")
  .UniqueResult<ProductDTO>();

Well this works well, a lot of people is using it…so, why may we want an alternative for this? Well in my case i don’t like so much to be forced to have the constructor + the import + the new ProductDTO…that’s a lot of info i have to give in the mapping simply to get a DTO…

Using the uNHAddins PositionalToBeanResultTransformer you can avoid the constructor and the import. What you still need is a query for sure. But instead of telling you are returning a new ProductDTO, you return the product.Code and product.Description…then you let the Transformer to do all the work for you.

So the definition of the Product DTO and the query are now:

public class ProductDTO
{
  public virtual string Code { get; set; }
  public virtual double Description { get; set; }
}

<query name="GetProductDTOCPositional">  
  select product.Code, product.Description  
  from Product product
</query>

Now you only need to instantiate an instance of PositionalToBeanTransformer telling it the type of the DTO as you would do with every transformer, but aditionally you tell it the name of the DTO properties that you are going to fill (static reflection will help here to avoid the strings) and you are done.

var transformer = 
new PositionalToBeanResultTransformer(typeof (ProductDTO), new[] {"Code", "Description"});
var productDTO = 
  session.GetNamedQuery("GetProductDTOPositional")
  .SetResultTransformer(transformer)
  .UniqueResult<ProductDTO>();

well this is less code, so for sure is a good alternative i feel some people may be against having properties and prefer readonly + constructor…well for this you should continue using the classical solution…but for those of us not concerned on this…this is a nice solution…

ToUpper and Trim string IUserTypes

noreply@blogger.com (Gustavo Ringel) — Fri, 20 Feb 2009 21:34:00 +0000

There are a lot of usable feature in uNHAddins…there is some people that i know that are using them. I think that it is a pity if people doesn’t get acquainted of this and implement it their selves once and once again…so i’m trying to post as much as i can about them…

In a previous post i introduced the EncryptedString IUserType and how to use it including some typedef variations.

There are two more user types there that you can use in some applications, or you can get ideas from them for some special cases.

One of them is called UpperString and what it does in short is converting the string to upper case…so if you need to send this to the application to avoid case sensitivity or whatever…you may use it, if it is not a domain concern (it is almost never a domain concern)

The second IUserType is called TrimString…it solves a problem i found mostly working with legacy databases where you have a CHAR(N) field, and you get for example “100 “ instead of “100” from the database. So if you suffer from this, then this is the IUserType for you…

We are thinking on adding some parameters to this to decide if doing Right Trim, Left Trim, trimming some special character not only spaces…but i’m not sure if it worth, even if it is very simple to do it…if someone needs this i can add it for sure…

uNHAddins conversation additions

noreply@blogger.com (Gustavo Ringel) — Fri, 20 Feb 2009 09:42:00 +0000

Well Fabio and i discussed some ideas…as always i only started thinking about how to implement them and he already had a complete solution for the things being discussed.

At least to feel I collaborate I will resume some of the things Fabio had been working on.

I added the new features to my sample project which was previously described here so i could play a little with tests. I also did it only looking at the code and svn log to feel how descriptive it was by itself.

Well, there are some things very new and some things that where missing an implementation...

First of all the MethodsIncludeMode property for the PersistenceConversational attribute is working, you can set it to Implicit or Explicit. Implicit will asume every public virtual method is part of a persistence conversation and will use the defaults if you don’t mark it as PersistenceConversation with your own properties. Explicit will consider only methods marked by you as part of the conversation.

Next we had a DefaultEndMode which was there but was not plugged in, now you can use it so every conversation will use as the default, if you want to do crazy things like set every method with EndMode.End, well, it is easy to do it even if not so right :)

Last but not least we can now set a ConversationConfigurationInterceptor either explicitly or injecting it using meantime the CastleAdapter. This means for example I can subscribe to every event of the conversation and explicitly do something if needed without doing a lot of work like i did in this post

The way to set an explicit Interceptor is having a class that inherits from IConversationCreationInterceptor which will have to implement the Configure method which receives a conversation, there you attach your events to the conversation and it is done. In the [PersistenceConversational] attribute you just set ConversationCreationInterceptor = typeof(MyInterceptor)

The DI way is creating a generic interceptor class that inherits from IConversationCreationInterceptorConvention<T> where T : class, the implementation is the same and it can be associated to a model implementing a generic class which receives a model and implements the interface. This will work if the property UseConversationCreationInterceptorConvention of PersistenceConversational is set to true (which is the default).

Well you can look at the code to see it working.

Encrypting password (or other strings) in NHibernate

noreply@blogger.com (Gustavo Ringel) — Thu, 19 Feb 2009 07:21:00 +0000

As you can read in every forum the solution to encrypting/decrypting a password is using an IUserType. Implementing an IUserType in NH is somewhat easy, so we added to uNHAddins a user type which will do the encryption.

The source code can be grabbed from uNHAddins trunk.

If you use it “as is” you will get an encryption using the symmetric algorithm DESCryptoServiceProvider. There is no special decision for this but to have some default option to do the job.

There are several ways to use the user type, the most common but less recommended (unless you are using it only once):

<property name="Password" type="uNHAddIns.UserTypes.EncryptedString, uNHAddins" />

The preferred way will be using <typedef> to define the user type as in the following:

<typedef class="uNHAddIns.UserTypes.EncryptedString, uNHAddIns" name="Encrypted">
  <param name="encryptor">uNhAddIns.UserTypes.uNHAddinsEncryptor, uNhAddIns</param>
  <param name="encryptionKey">myRGBKey</param>
</typedef>

The parameters are optional but give you an easy option to extend the user type to use your own algorithm.

The encryptor paramater expects an implementation of IEncryptor, if you don’t set it you get the uNHAddinsEncryptor implementation. Implementing the interface is very easy you just need to say how you encrypt and decrypt and if you want to use an external key set in the typedef parameters then you can get this using the EncryptionKey property.

public interface IEncryptor
{
  string Encrypt(string password);
  string Decrypt(string encryptedPassword);
  string EncryptionKey { get; set; }
}

Using it now in your code is as easy as:

<property name="Password" type="Encrypted" />

The Password property keeps being implemented as a string, so you don’t touch your existing code.

Changing a log entry using svn

noreply@blogger.com (Gustavo Ringel) — Mon, 16 Feb 2009 09:50:00 +0000

Warn: This is more a personal reminder, than a post…but someone may find it useful

Today i was working in two solutions at the same time, and committed one of them thinking I’m committing the other one…dumb of me.

So, i thought ok, big deal, went to the tortoise log and changed the log message, when I tried to change it, received this nice message box:

Ok, first i found a template at the hooks directory of the repository called pre-revprop-change.tmpl which i can use to explicitly say that an specific revision was changed. This is the best solution as far as i read because every notification, etc will work as usual. But i did want to continue working and solve this error fast, and for now i’m not concerned in bypassing this for a while.

So i found this line i can execute in svn to bypass the hooks:

svnadmin setlog --bypass-hooks REPOS_PATH -r N

Where REPOS_PATH is the local path for a subversion repository (i executed this in the server) and N is the number of the revision…

I almost never had to do this, but i put me a reminder if a i need it in the future.

Why I like to work with NHibernate trunk…

noreply@blogger.com (Gustavo Ringel) — Sat, 14 Feb 2009 21:30:00 +0000

Last days i was using for several times the syntax SetParameter<T>(string, object). The code for this is a shortcut to SetParameter(string, object, IType).

Using it in code in the first option looks like SetParameter<Entity>(“param”, value)

The second syntax will be SetParameter(“param”, value, NHibernateUtil.Entity(tyepof(Entity))

I’m almost sure for every one the first syntax will be prettier than the second one, I need to know and remember that NHibernateUtil also…

I can download de trunk and run the tests…so i know that mostly every thing that worked will still work. I get the syntactic sugar and new fuctionalty for my current code…good enough.

The only drawback…when i have to maintain code not using the trunk i suffer a little more.

Changing the default conversation factory for uNHAddins

noreply@blogger.com (Gustavo Ringel) — Thu, 12 Feb 2009 23:06:00 +0000

Before i started using the uNHAddins conversation i was using Castle ATM + NHibernate Integration. In some cases i did have to execute an action immediately after the transaction is committed. I did this enlisting an ISynchronize object to the ITransactionManager and then Castle handled this call.

Now i was in the need of doing the same thing using uNHAddins. I chatted a little bit with Fabio, and at the end we found that it is very easy to extend uNHAddins to have this behavior. All i had to do was implementing my own ConversationFactory, i decided to call it NotifiableConversationFactory.

My implementation is:

public class NotifiableConversationFactory : IConversationFactory
 {
  private readonly ISessionFactoryProvider factoriesProvider;
  private readonly ISessionWrapper wrapper;
  public NotifiableConversationFactory(ISessionFactoryProvider factoriesProvider, ISessionWrapper wrapper)
  {
   this.factoriesProvider = factoriesProvider;
   this.wrapper = wrapper;
  }
  public IConversation CreateConversation()
  {
   return new NhConversation(factoriesProvider, wrapper);
  }
  public IConversation CreateConversation(string conversationId)
  {
   var result = new NhConversation(factoriesProvider, wrapper, conversationId);
   if (conversationId.StartsWith("Notify"))
   {
    result.Ended += EventSource.Conversation_Ended;
   }
   return result;
  }
 }

I’m not so happy about the string “Notify” there but this is more a proof of concept than a real implementation.

What i’m checking there is if i’m called by a conversation with IdPrefix = “Notify”. IdPrefix is a handy property of PersistenceConversational which permits adding a prefix to the conversation id so i can detect if this conversation is some type of conversation i prefix this way.

So in the class you want to register the events you must have:

[PersistenceConversational(IdPrefix = "Notify")]

An example as always can be find in the sessionManagement example at uNHAddins. The IModifyOrderModel is notifying (log) about the end of the conversation.

uNHAddins Persistence Conversation – Part 2: Configuring the conversation

noreply@blogger.com (Gustavo Ringel) — Sun, 08 Feb 2009 20:56:00 +0000

In the first post I showed how to configure the uNHAddins conversation. Now I will show how to use the PersistenceConversation aspects to manage a uNHAddins conversation.

A class which will rule a conversation should be marked as [PersistenceConversational] every public method that is part of a conversation should be marked as [PersistenceConversation].

In the example code we have the interface

public interface IModifyOrderModel
{
  PurchaseOrder FindOrderOrCreateNew(string number, DateTime dateTime);
  void Persist(PurchaseOrder order);
  void AbortConversation();
}

which is implemented by the ModifyOrderModel class:

[PersistenceConversational]
public class ModifyOrderModel : IModifyOrderModel
{
private readonly IOrderRepository orderRepository;
public ModifyOrderModel(IOrderRepository orderRepository)
{
  this.orderRepository = orderRepository;
}
[PersistenceConversation(ConversationEndMode = EndMode.Abort)]
public void AbortConversation()
{  // Rollback the use case }
[PersistenceConversation]
public PurchaseOrder FindOrderOrCreateNew(string number, DateTime dateTime)
{
  var order = orderRepository.GetOrderByNumberAndDate(number, dateTime.Date);
  if (order == null)
  { order = new PurchaseOrder { Date = dateTime, Number = number }; }
  return order;
}
   [PersistenceConversation(ConversationEndMode = EndMode.End)]
   public void Persist(PurchaseOrder order)
   {
   orderRepository.MakePersistent(order);
   }
}

This class manages the order modification conversation. As you see we don’t have references to NHibernate at this point. We do have an IOrderRepository which is going to provide the data we need for the conversation.

The implementation of the repository in the example is very simple, one important thing to notice is that we are injecting an ISessionFactory:

public class OrderRepository : Repository<PurchaseOrder>, IOrderRepository
{
public OrderRepository(ISessionFactory sessionFactory) : base(sessionFactory) { }
public PurchaseOrder GetOrderByNumberAndDate(string number, DateTime dateTime)
{
 var query = Session.GetNamedQuery("GetOrderByNumberAndDate").SetParameter("number", number).SetParameter("dateTime", dateTime); 
 return query.UniqueResult<PurchaseOrder>();
}
}

The Repository<T> is a very thin class which gives minimum CRUD implementations using NH. The interesting part is how we are getting a session:

protected ISession Session
{
  get { return factory.GetCurrentSession(); }
}

From the doc: GetCurrentSession() Obtains the current session. The definition of what exactly "current" means controlled by the CurrentSessionContext impl configured for use

In our case if you remember from the first post we are using the uNHAddins ThreadLocalConversationalSessionContext, which in general is good enough for a Windows Forms Application.

You may have noticed a property ConversationalEndMode in the PersistenceConversation attribute, for now there are three options:

EndMode.Continue: Can start a conversation and lives it alive.

EndMode.End: Flushes the session and commits current transactions, then it disposes the session

EndMode.Abort: Disposes the session (without accepting the changes)

Basically this is it. In the example code you can find an application using MVP with this ideas. Feel free to comment / ask in the uNHAddins forum about it.

uNHaddins Persistence Conversation – Part 1: Configuration

noreply@blogger.com (Gustavo Ringel) — Fri, 06 Feb 2009 16:53:00 +0000

uNHAddins Conversation and motivations where widely presented on Fabio’s blog here.

The focus of this series of posts is configuring the Persistence Conversation aspect using uNHAddins and CastleAdapter targeting a Windows Forms Application (some of the concepts are easily movable to a Web application, but there are much more frameworks and examples matching this)

A working example can be found in the examples folder of uNHAddins trunk, here.

The following assumptions are made about your repositories/Dao’s for this to work.

1) You are injecting the ISessionFactory in the repositories and not an ISession.

2) You are using GetCurrentSession() instead of OpenSession() to get the active session inside the repositories / dao’s.

3) You are able to use Castle for Dependency Injection, i hope more adapters will come in the future, but this is one that it is implemented and it is enough popular.

First thing we should do is to decide the conversation context strategy and set it in the hibernate cfg. For this example it is:

<property name="current_session_context_class"> 
uNhAddIns.SessionEasier.Conversations.ThreadLocalConversationalSessionContext, uNhAddIns 
</property>

Next thing is configuring castle to accept the PersistenceConversationalFacility, which will bring AOP in a similar manner to the TransactionalFacility from castle, and all the factories and services that compose a conversation.

The configuration for the facilities and default uNHAddins components for Castle can be found here . There are some cases when you will want to play with the factories, this will be the reason for another post.

Finally you set the way you are going to create sessions in your application (sessionFactory provider is the id to an implementation of ISessionFactoryProvider)

<component id="uNhAddIns.sessionFactory"
      type="NHibernate.ISessionFactory, NHibernate"
      factoryId="sessionFactoryProvider"
      factoryCreate="GetFactory">
      <parameters>
        <factoryId>uNhAddIns</factoryId>
      </parameters>
</component>

This is all the magic we need to set it up all. The following post will be about using it in our application.

If you want to see it working follow the link to the source at the beginning of the post.