Organizing Packages: Feature vs Layer

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41

package com.example.orders;

import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;
import org.springframework.data.jpa.repository.JpaRepository;
import jakarta.persistence.*;
import java.util.UUID;

// 1. Public HTTP Entry Point
@RestController
@RequestMapping("/api/orders")
class OrderController {
    private final OrderService service;
    OrderController(OrderService service) { this.service = service; }
    @GetMapping("/{id}")
    OrderResponse get(@PathVariable UUID id) { return service.find(id); }
}

// 2. Public Service Boundary
@Service
public class OrderService {
    private final OrderRepository repository;
    OrderService(OrderRepository repository) { this.repository = repository; }
    public OrderResponse find(UUID id) {
        return repository.findById(id)
            .map(e -> new OrderResponse(e.getId()))
            .orElseThrow();
    }
}

// 3. Package-Private Persistence (Hidden from other packages)
interface OrderRepository extends JpaRepository<OrderEntity, UUID> {}

@Entity
@Table(name = "orders")
class OrderEntity {
    @Id private UUID id;
    UUID getId() { return id; }
}

public record OrderResponse(UUID id) {}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

package com.example.architecture;

import com.tngtech.archunit.junit.AnalyzeClasses;
import com.tngtech.archunit.junit.ArchTest;
import com.tngtech.archunit.lang.ArchRule;
import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noClasses;

@AnalyzeClasses(packages = "com.example") 
public class ArchitectureTest {

    @ArchTest
    static final ArchRule controllersMustNotDependOnRepositories =
        noClasses().that().haveSimpleNameEndingWith("Controller")
            .should().dependOnClassesThat().haveSimpleNameEndingWith("Repository")
            .because("Controllers must delegate through Service facades.");
}