CODEWITHSUNDEEP
springdomain-driven-designdesign-patternspojo
Jany
Jany

Reputation: 73

Domain Driven Programming Using Spring

I have a question on DDD & Spring. I always design my application around anemic domain model and service taking care of business logic/persistence.

Assume you have a spring managed persistence/respository service for a Domain object e.g. Book. If I have to expose a save() method on book then i will need repository bean inside my domain or i will have to look up the context for the repository bean. Which is exactly opposite of Dependency Injection.

Now, If I have repository id injected into domain and domain object is cached ( clustered cache) and then on deserialization it will not have the injected repository service as spring containers will be different.

I might be wrong but if someone can explain me how this scenario will work, it would be of great help

Upvotes: 1

Views: 481

Answers (2)

Mr.Eddart
Mr.Eddart

Reputation: 10273

I think that the "facade" of your application should use a Repository (or other infrastructure service) to save the "book". The book should not save it-self, this is responsibility of the Repository.

If you need to make any infrastructure operation (for example, search the database) from a Domain Entity, then you should gain access to this Repository by looking up the context (and getting coupled to Spring as a result) or injecting the Repository through Dependency Injection in the Entity.

The problem is that the "instantiation" of the Entity is not responsibility of Spring but of the Persistence Provider, so Spring cannot handle this injection. What to do?

Well, there are several ways (none of them very "beautyful") to do this:

  • Through AOP: you can instrument the code with Aspect Oriented Framework (like AspectJ) configuring the system to inject whatever dependency in the Entity in the instantiation moment.
  • Through a Hibernate interceptor: if your Persistence Provider is Hibernate, it offers you a hook to place interceptors in certain points of the life cycle of the Entities. You can configure an interceptor that looks-up the spring context to inject dependencies in the instantiation of every Entity.
  • Maybe the easiest way is to implement a little and static "serviceLocator" coupled with spring that looks-up services asked by the Entities when they need them. This service locator is just a layer to avoid your entities to get coupled to Spring.

Upvotes: 2

agranjo
agranjo

Reputation: 1374

I think that a "save" method (save in a DB, in example) doesn't belong to the domain object... Does the book "save" itself? Or is the repository saving it?...

Upvotes: 1

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