Nrthugu

Sometimes Spring components may look like this:

@Service

public final class SomeService {

    @Autowired

    private SomeService2 someService2;

    @Autowired

    private SomeService3 someService3;

    @Autowired

    private SomeService4 someService4;

    // … and many other services

    @Autowired

    private SomeDao someDao;

    @Autowired

    private SomeDao2 someDao2;

    @Autowired

    private SomeDao3 someDao3;

    // … and many other DAOs



}

In other words Spring components have plenty services and DAOs that are mostly repeated in other Spring components. IMHO it has the following drawbacks:

• Unnecessary (boilerplate) code for autowiring most of the same components


• Sometimes Spring context loading error may occur due to circular references between components

What about to use all-in-one component that combine, say, all services or all DAOs. It will contain only links to Spring components with no any bussiness logic inside:

@Service

public final class AllServices {

    @Autowired

    private SomeService2 someService2;

    @Autowired

    private SomeService3 someService3;

    @Autowired

    private SomeService4 someService4;

    // … and many other services



    // get methods to get some service

    public someService getSomeService(){};

and inject it into other components:

@Service

public final class SomeService {

    @Autowired

    private AllServices serv;

    @Autowired

    private AllDaos daos;

    @Autowired

    private Environment env;



// inside some code

…

serv.getSomeService().processData();

IMHO it will look more succinct without circular references issues…

What pros and cons of this approach?

The second approach might look appealing, a well-known facade pattern comes to mind at first, so I can totally understand this.

However, I think the first pattern will work better in fact and here is why:

1. 
   

   You say that the "all-mighty" service can solve circular dependencies

   
   
   

   Well, circular dependencies usually point on a wrong / bad design and are code smell by there own, so hiding it behind a facade won't improve the system, resolving the circular dependencies will. In addition if from the actual services, called by "AllServices" you'll want to invoke additional service (again, bad design is preserved) then the code will probably pass through AllServices again, and hence the circular dependency is still there.

   
   



2. Using the second design assumes that this "AllServices" class will be used by all the components of the system, but in this case it becomes a "one-central-point" and refactoring in this class can turn to a madness - all the components / their tests might be affected




3. Initialization of this service can become a mess by itself, since you probably won't want to maintain a constructor that has 20-30 input parameters you'll resort to field injection (like in the example) which is bad by its own because if you want to initialize it somehow, probably from test, or something you want know what should be mocked and what not, in which order, and so forth.

Second approach may look cleaner, but it will be difficult to know which service is connected to service/DAO and therefore it will be hard to refactor or do/decide on which regression any change will cause. Meaning it effect software flexibility

This is the important difference which make the difference to choose first option IMHO