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Archive for April, 2011

NHibernate working with Unsigned Value types like uint, sbyte, short etc.

April 30th, 2011 No comments

NHibernate working with Unsigned Value types like uint, sbyte, short etc.

We want to share one of the first experiences during developing with NHibernate. We immediately bumped in to serious problem with supporting unsigned Value types like

uint, ulong, sbyte

etc .  Natively those types are not fully supported by NHibernate.

You probably will ask “why we need those types?” Data that comes in some special formatting binary way form streaming where packet size is very important, so many optimizations are used. Our task was deserialize those compressed messages and at the end all data have to be stored in database tables. Additional that affected on our solution was demand to serialize data back to binary format from database tables.

The simplest and fast solutions were to duplicate properties int and uint but this was very ugly and not developer friendly proposal (from our point of view of cause). Additionally we have had plenty of such unsigned fields.

private uint m_value;

 

private int VlaueInt

{

get{ return (int)m_value;}

set { m_value = (uint)value; }

}

 

 

public uint ValueUint

{

get { return m_value; }

set { m_value = value; }

}

The second option were implementation of IUserType which means I have to create type that NHibernate can work with, but this solution wasn’t an option for us as well, because we didn’t wanted that our users that are going to use those Types will be aware of NHibernate existence. What will happen if we will choose to move all our data model to Entity framework for example.

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Categories: .Net, C#, NHibernate Tags:

Working with System.Timers.Timer causing memory leaks

April 21st, 2011 2 comments

Short preamble,

Recently we had very serious problem with our application written in C#.NET; sometimes it has been completely stuck. This wasn’t easy reproducible scenario. As we started investigate the issue and debugging, more and more interesting things came up (not all code was written by our team, so debugging was not very easy thing). Memory almost wasn’t affected, but there was another symptom: thread count was growing and growing.

Finally the problem was discovered as following:
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Categories: .Net, C# Tags: , , ,

How to find all types which derive from given type.

April 16th, 2011 No comments

Suppose you need to find all types in assembly, which derive from given type (using C#.NET). What we need is reflection, to collect all types in a given assembly, using “Assembly.GetTypes” and then to select the required types only.

1) As a first attempt, we will use a function “IsSubclassOf” for every type in assembly:

public IEnumerable<Type> GetAllTypesDerivedFrom(Type type)
{
        var types = Assembly.GetAssembly(type).GetTypes();
        return types.Where(curType => curType.IsSubclassOf(type));
}

This works good. So, why this attempt is not a solution? Because the function “IsSubclassOf” works with classes, but not with interfaces. It returns “false” for interface.
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Categories: .Net, C# Tags: ,

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April 14th, 2011 No comments

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Categories: General Tags:

How to do mapping of NCLOB into string in NHibernate

April 11th, 2011 2 comments

I want to describe some error, which is accepted, while mapping NCLOB in NHibernate.

Working with Oracle database, we use “NVARCHAR2” type for strings. But this type has a constrain: it could contain no more then 2000 characters. If one needs to store some long text in Oracle, he will use an NCLOB type.

But, while mapping this type, next error is accepted:
ORA-01461: can bind a LONG value only for insert into a LONG column“.

How can we avoid this error? Two ways are possible:

1) Setting coulumn’s type to “AnsiString”:

        <property name="Contents" column="CONTENTS" type="AnsiString"/> 

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Categories: .Net, NHibernate Tags: , , , , ,

A problem with using static member in a class C#.NET

April 9th, 2011 3 comments

Today, I would like to tell about some bug I had in my C#.NET code, and a simple way to fix it.

When needed a transform matrix 3 x 3, I wrote a simple class Matrix3X3; this class includes static feilds “Zero” and “Ones” for Zero-Matrix and Ones-Matrix appropriately.
Let’s take a brief look of the implementation:

class Matrix3X3
{
        public static Matrix3X3 Zero = new Matrix3X3(0);
        public static Matrix3X3 Ones = new Matrix3X3(1);

        // class members ...

        public Matrix3X3(double value)
        {
                // Fill the whole matrix with same value.
                // ...
        }

        // class methods ...
}

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Categories: .Net Tags: , , ,

EJB3 Asynchronous messaging with WebSphere7.0

April 2nd, 2011 9 comments

In enterprise applications when you have to delivery a message and even if the destination is down and you do not want to wait for a response in real time we better use JMS to work with asynchronous messaging. A Message Driven Bean is a stateless enterprise bean. A container typically manages a pool ed advanced lite set of such objects. As messages arrive, the container will take an MDB from the pool cytoxan and have it process a message. If the processing succeeds, the message is removed from the queue; otherwise

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it remains on the queue. Basically, we can create a JMS component using the annotation @ MessageDriven and also implementing the interface java.jms.MessageListener. In this article, we will create a simple example and then deploy it/test it on Websphere 7.0 with EJB3 Feature Pack.

Setting up the JMS Provider and the Destination

We will use WebSphere Application Server 7.0 JMS Provider. In my antabuse previous Asynchronous messaging using JMS on WebSphere 7.0 article I have demonstrated how to create an Integration Bus, JMS Provider, Connection Factory, Destination and Activation specifications in WebSphere 7.0 so I will assume that we are familiar with that. Read more…

Categories: Java Tags: , ,