Organization of services in service layer?
I have a Java server application with a ton of different entities. So far, each entity top开发者_高级运维 level entity has its own CRUD service. By top level, I mean the root of a tree of entities that can stand alone.
Now I am getting into the heart of my Flex client and find I am needing/writing many different queries. But where best to put these queries?
Say for example, I have a query to find all "foos" based on their associate with a certain "bar". Currently that query is on the "foo" service (findAllByBar), but I am finding that it would be very convenient to have it (also?) in the "bar" service (findFoos). On the other hand, I could also create a query service and lump all the queries in there.
Whats a good practice to do here?
Try to layer your application in these perspectives:
Domain: design your class as entities like "Customer", value objects like "Address" or "Color", and aggregate roots (like "Order" which includes a list of "LineItem")
Repositories: these are the data access for the entities, create a repository for each aggregat root (CustomerRepository, OrderRepository, ...)
Services: create a coarse grained services spitted by logical business abstractions or bounded context not by entities, it is not logical to create a service for order and a service for items and a service for customers when all these entities are representing one atomic business value of order processing, then your service will use all required repositories to handle the data access.
example:
public class OrderRepository {
public Foo getById(int id) {
//
}
public Foo getByCustomer(Customer customer) {
//
}
}
public class CustomerRepository {
public Foo getById(int id) {
//
}
public Foo getByUserName(string userName) {
//
}
}
public class TradingService {
private OrderRepository _orderRepository;
private CustomerRepository _customerRepository;
public TradingService(OrderRepositoryInterface orderRep, CustomerRepositoryInterface cusRep) {
_orderRepository = orderRep;
_customerRepository = custRep;
}
public void placeOrder(string customerUserName, Order order) {
Customer customer = _customerRepository.getByUserName(customerUserName);
order.setCustomer(customer);
_orderRepository.add(order);
// ....
}
}
I would put queries in their respective classes instead of creating one (bloatable)query service
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