Spring.Net HibernateTemplate.Execute Clarification - nhibernate

Question

I am taking over a project that was written by third party consultants who have already left.
I come from EF backgournd. One of the DAO class has the following which I find very hard to get my head around on details of what is exactly happening step by step. If anyone could kindly help me to understand this code section will be much appreciated.
return HibernateTemplate.Execute(
delegate(ISession hbSession) // <<--What is this code actually trying to do?
{
string queryText = "from {0} x where x.Code = :Code";
queryText = string.Format(queryText, typeof(Product));
IQuery query = hbSession.CreateQuery(queryText);
query.SetParameter("Code", productCode);
query.SetCacheable(true);
query.SetCacheRegion(CoreCacheConstants.ProductQueryCacheRegion); // <-- What is this code trying to do.
var fund = query.UniqueResult(); // <-- Is this similar to DISTINCT keyword in LINQ?
if (fund == null)
throw new ArgumentException(String.Format("No product found with productcode: {0}", productCode: ));
NHibernateUtil.Initialize(((Product)Product).Details); // <--What is this code trying to do. And where is the execute method for above queries.
return fund;
}
) as Product
Basically I am confused with delegate part and why delegate is being used instead of simple query to database. And what is the benefit of above approach.
Also I cant see any nHibernate ORM mapping xml. Does Spring.NET requires mapping files in order to pass data from/to data source?In order words how does ISession knows which database to connect to and which table to use etc

Answer 1

This is what in the spring documents is referred to as Classic Hibernate Usage. It is not the currently recommended approach to work with NHibernate, which is described in the chapter on object relational mappers.
The "convenient" usage of delegates here is basically done to provide the HibernateTemplate the means to manage a session and hand this managed session over to other custom methods (in this particular case an anonymous method). (I think it's an implementation of the visitor pattern, btw).
Using this approach, the classic HibernateTemplate can provide functionality to methods it doesn't "know of", such as opening and closing sessions correctly and participating in transactions.
The query is actually being executed by HibernateTemplate.Execute(myMethod); I imagine it creates and initializes a session for you, does transaction management, executes your method with the managed session and cleans everything up.
I've never used HibernateTemplate, but I'm sure it would require mapping files and a SessionFactory, so if this code is hit during execution and doesn't throw any exceptions, the configuration for those has to be there somewhere!
With respect to the questions (besides the delegate part) within your posted code: the use of NHibernateTemplate hasn't really got anything to do with it: you can just as well run this code in any piece of code where you've got hold of a valid ISession instance:
the session executes a HQL query; this query is added to the query cache. I've never used SetCacheRegion myself, but apparently it gives you "fine-grained control over query cache expiration policies".
query.UniqueResult
NHibernateUtil.Initialize