Suggestions on how to map from Domain (ORM) objects to Data Transfer Objects (DTO)
- by FryHard
The current system that I am working on makes use of Castle Activerecord to provide ORM (Object Relational Mapping) between the Domain objects and the database. This is all well and good and at most times actually works well!
The problem comes about with Castle Activerecords support for asynchronous execution, well, more specifically the SessionScope that manages the session that objects belong to. Long story short, bad stuff happens!
We are therefore looking for a way to easily convert (think automagically) from the Domain objects (who know that a DB exists and care) to the DTO object (who know nothing about the DB and care not for sessions, mapping attributes or all thing ORM).
Does anyone have suggestions on doing this. For the start I am looking for a basic One to One mapping of object. Domain object Person will be mapped to say PersonDTO. I do not want to do this manually since it is a waste.
Obviously reflection comes to mind, but I am hoping with some of the better IT knowledge floating around this site that "cooler" will be suggested.
Oh, I am working in C#, the ORM objects as said before a mapped with Castle ActiveRecord.
Example code:
By @ajmastrean's request I have linked to an example that I have (badly) mocked together. The example has a capture form, capture form controller, domain objects, activerecord repository and an async helper. It is slightly big (3MB) because I included the ActiveRecored dll's needed to get it running. You will need to create a database called ActiveRecordAsync on your local machine or just change the .config file.
Basic details of example:
The Capture Form
The capture form has a reference to the contoller
private CompanyCaptureController MyController { get; set; }
On initialise of the form it calls MyController.Load()
private void InitForm ()
{
MyController = new CompanyCaptureController(this);
MyController.Load();
}
This will return back to a method called LoadComplete()
public void LoadCompleted (Company loadCompany)
{
_context.Post(delegate
{
CurrentItem = loadCompany;
bindingSource.DataSource = CurrentItem;
bindingSource.ResetCurrentItem();
//TOTO: This line will thow the exception since the session scope used to fetch loadCompany is now gone.
grdEmployees.DataSource = loadCompany.Employees;
}, null);
}
}
this is where the "bad stuff" occurs, since we are using the child list of Company that is set as Lazy load.
The Controller
The controller has a Load method that was called from the form, it then calls the Asyc helper to asynchronously call the LoadCompany method and then return to the Capture form's LoadComplete method.
public void Load ()
{
new AsyncListLoad<Company>().BeginLoad(LoadCompany, Form.LoadCompleted);
}
The LoadCompany() method simply makes use of the Repository to find a know company.
public Company LoadCompany()
{
return ActiveRecordRepository<Company>.Find(Setup.company.Identifier);
}
The rest of the example is rather generic, it has two domain classes which inherit from a base class, a setup file to instert some data and the repository to provide the ActiveRecordMediator abilities.
