What is the difference between proxies, repositories and services in Doctrine 2?

Question

I am wondering what are the difference between those 3 patterns.

As far as I understand:

• Proxies are used only for lazy-load entities
• Repositories are used to add logic to your model (width some shortcut method for DQL statement)
• Services are used to rely models and controllers

For this last, services, I don't the point behind it with a Doctrine 2 project as repository are not aware of the persistent system behind, because it use the ORM with DBAL.

I read that proxies could be used to add logic to entities, so what's the difference with repositories?

By the way, should my Entities only contain public getter/setter to their attribute and only that? Is it correct?

I'm kind of lost here.

Do you have any concrete example?

Answer 1

A Proxy is a reference to something.

Suppose you are creating a User and one User has one Group attached. If you don't have Proxy support, you would need to do fetch on DB for the Group just to be able to use the Entity. Here is a possible code:

$group = $em->getRepository('Group')->findOneById(1);

With support to Proxies, you don't need to do the DB lookup. A Proxy is considered a reference to a DB thing, without actually fetching it. Your code:

$group = $em->getReference('Group', 1);

The benefit of having Proxy is simple... if you need to get (for example) the Group name, just do it normally: $group->getName(); And Proxy will initialize the Entity (DB fetch on-demand).

A Repository is a data manipulation thing. You use it to manage your Entities. So you can findById, findOneByEmail, etc. You can also extend its basic functionality and implement your own methods that manage your Entities, like: saveUser, retrieveMostActiveUsers.

A Service uses Repositories internally, but it contains more validation and may interact with > 1 Repository. For example, after you successfully save the user, you would like to send him a Congrat email. So inside your createUser method of UserService, you retrieve the NotificationService and dispatch the new registration email.

Is it clear for you now? =)

Cheers,