Toluu : The NHibernate FAQ

The NHibernate FAQ

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Type analyzer - Interesting findingsDecember 1 2008

When reading this post from Ayende I was getting curious what this site would tell about my blogging style here. The result is amusing me a lot.

INTJ - The Scientists

The long-range thinking and individualistic type. They are especially good at looking at almost anything and figuring out a way of improving it - often with a highly creative and imaginative touch. They are intellectually curious and daring, but might be physically hesitant to try new things.
The Scientists enjoy theoretical work that allows them to use their strong minds and bold creativity. Since they tend to be so abstract and theoretical in their communication they often have a problem communicating their visions to other people and need to learn patience and use concrete examples. Since they are extremely good at concentrating they often have no trouble working alone.

I would be very pleased if you could provide some feedback about what you are thinking of this findings... Especially interesting is the question whether

I am too abstract or theoretical
I can communicate my visions to you
My examples are concrete enough

Linq to NHibernateNovember 26 2008

The popularity of NHibernate is steadily increasing. At the same time people get used to LINQ. Now there exists a LINQ to NHibernate provider since quite some time. It's not a complete implementation of a LINQ provider but it is still quite useful. Most of the day to day problems we face when developing typical business application can be solved by using this provider. And if there is a query that cannot be executed against the provider we still have the option to falling back to the hibernate query language (HQL).

In this post I'll give you an introduction on how you can use NHibernate in conjunction with LINQ. Let's start with the definition of a domain model we are going to use when querying the database by using LINQ expressions or LINQ query operators.

The domain model

I have the following simple domain model. A person can have a set of assigned tasks.

The entities

I want to keep the entities as simple as possible for this example. So their implementation is as follows

First and Second Level caching in NHibernateNovember 9 2008

I'll try to dive deep into the caching of NHibernate in this article. This post has been inspired by the talk given by Oren Eini (aka Ayende) at the Kaizen Conference in Austin TX.

Caching is a topic that is IMHO only superficially described so far especially regarding the second level cache. Most of the time one finds a lot of information about how to configure a specific cache provider for usage but the real usage (who and when) is not really described. I hope to be able to provide some of the missing pieces with this post.

The full source code used for this post can be found here.

First Level Cache

When using NHibernate the first level cache is automatically enabled as long as one uses the standard session object. We can avoid to use a cache at all when using the stateless session provided by NHibernate though. The stateless session is especially useful for reporting situations or for batch processing. When NHibernate is loading an entity by its unique id from the database then it is automatically put into the so called identity map. This identity map represents the first level cache.
The life-time of the first level cache is coupled to the current session. As soon as the current session is closed the content of the respective first level cache is cleared. Once an entity is in the

The Repository PatternOctober 8 2008

Introduction

When accessing data from a data source we have several well documented possibilities. Martin Fowler e.g. describes several of them in his PoEAA book.

Table data gateway
Row data gateway
Active record
Data mapper

When applying DDD (domain driven design) we often use the so called Repository Pattern to access the data needed by the domain model.

What is a Repository

Martin Fowler writes:

"A Repository mediates between the domain and data mapping layers, acting like an in-memory domain object collection. Client objects construct query specifications declaratively and submit them to Repository for satisfaction. Objects can be added to and removed from the Repository, as they can from a simple collection of objects, and the mapping code encapsulated by the Repository will carry out the appropriate operations behind the scenes. Conceptually, a Repository encapsulates the set of objects persisted in a data store and the operations performed over them, providing a more object-oriented view of the persistence layer. Repository also supports the objective of achieving a clean separation and one-way dependency between the domain and data mapping layers."

Implementation

In DDD we have the notion

A fluent interface to NHibernate - Part 4 - ConfigurationAugust 26 2008

This is the fourth post in a series of articles where I want to analyze and describe the new upcoming mapping interface providing a fluent interface to NHibernate for the mapping of a domain model to the underlying database. The previous post are

Configuration

In NHibernate we traditionally had several methods how we could configure the database relevant parameters. These are

defining all requested configuration parameters in code
include a special section in the app.config or web.config file
define a hibernate.cfg.xml file
define a custom XML file

With the new mapping framework we have one more possibility by using a fluent interface to configure NHibernate. We can define all parameters in our code using a fluent interface. Let's review the various methods to configure our ORM framework.

Toluu