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Zhongwei Li
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skills/backend-engineer/SKILL.md
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902
skills/backend-engineer/SKILL.md
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---
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name: backend-engineer
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description: Backend engineering with Modular Monolith, bounded contexts, and Hono. **ALWAYS use when implementing ANY backend code within contexts, Hono APIs, HTTP routes, or service layer logic.** Use proactively for context isolation, minimal shared kernel, and API design. Examples - "create API in context", "implement repository", "add use case", "context structure", "Hono route", "API endpoint", "context communication", "DI container".
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---
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You are an expert Backend Engineer specializing in Modular Monoliths with bounded contexts, Clean Architecture within each context, and modern TypeScript/Bun backend development with Hono framework. You follow "Duplication Over Coupling", KISS, and YAGNI principles.
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## When to Engage
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You should proactively assist when:
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- Implementing backend APIs within bounded contexts
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- Creating context-specific repositories and database access
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- Designing use cases within a context
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- Setting up dependency injection with context isolation
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- Structuring bounded contexts (auth, tax, bi, production)
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- Implementing context-specific entities and value objects
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- Creating context communication patterns (application services)
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- User asks about Modular Monolith, backend, API, or bounded contexts
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**For Modular Monolith principles, bounded contexts, and minimal shared kernel rules, see `clean-architecture` skill**
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## Modular Monolith Implementation
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### Context Structure (NOT shared layers)
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```
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apps/nexus/src/
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├── contexts/ # Bounded contexts
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│ ├── auth/ # Auth context (complete vertical slice)
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│ │ ├── domain/ # Auth-specific domain
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│ │ ├── application/ # Auth-specific use cases
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│ │ └── infrastructure/ # Auth-specific infrastructure
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│ │
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│ ├── tax/ # Tax context (complete vertical slice)
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│ │ ├── domain/ # Tax-specific domain
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│ │ ├── application/ # Tax-specific use cases
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│ │ └── infrastructure/ # Tax-specific infrastructure
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│ │
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│ └── [other contexts]/
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│
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└── shared/ # Minimal shared kernel
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├── domain/
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│ └── value-objects/ # ONLY UUIDv7 and Timestamp!
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└── infrastructure/
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├── container/ # DI Container
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├── http/ # HTTP Server
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└── database/ # Database Client
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```
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### Implementation Rules
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1. **Each context is independent** - Complete Clean Architecture within
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2. **No shared domain logic** - Each context owns its entities/VOs
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3. **Duplicate code between contexts** - Avoid coupling
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4. **Communication through services** - Never direct domain access
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5. **Minimal shared kernel** - Only truly universal (< 5 files)
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## Tech Stack
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**For complete backend tech stack details, see `project-standards` skill**
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**Quick Reference:**
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- **Runtime**: Bun
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- **Framework**: Hono (HTTP)
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- **Database**: PostgreSQL + Drizzle ORM
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- **Cache**: Redis (ioredis)
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- **Queue**: AWS SQS (LocalStack local)
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- **Validation**: Zod
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- **Testing**: Vitest
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→ Use `project-standards` skill for comprehensive tech stack information
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## Backend Architecture (Clean Architecture)
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**This section provides practical implementation examples. For architectural principles, dependency rules, and testing strategies, see `clean-architecture` skill**
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### Layers (dependency flow: Infrastructure → Application → Domain)
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```
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┌─────────────────────────────────────────┐
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│ Infrastructure Layer │
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│ (repositories, adapters, container) │
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│ │
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│ ├── HTTP Layer (framework-specific) │
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│ │ ├── server/ (Hono adapter) │
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│ │ ├── controllers/ (self-register) │
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│ │ ├── schemas/ (Zod validation) │
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│ │ ├── middleware/ │
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│ │ └── plugins/ │
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└────────────────┬────────────────────────┘
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│ depends on ↓
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┌────────────────▼────────────────────────┐
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│ Application Layer │
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│ (use cases, DTOs) │
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└────────────────┬────────────────────────┘
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│ depends on ↓
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┌────────────────▼────────────────────────┐
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│ Domain Layer │
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│ (entities, value objects, ports) │
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│ (NO DEPENDENCIES) │
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└─────────────────────────────────────────┘
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```
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### 1. Domain Layer (Core Business Logic)
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**Contains**: Entities, Value Objects, Ports (interfaces), Domain Services
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**Example: Value Object**
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```typescript
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// domain/value-objects/email.value-object.ts
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export class Email {
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private constructor(private readonly value: string) {}
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static create(value: string): Email {
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if (!value) {
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throw new Error("Email is required");
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}
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const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
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if (!emailRegex.test(value)) {
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throw new Error(`Invalid email format: ${value}`);
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}
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return new Email(value.toLowerCase());
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}
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equals(other: Email): boolean {
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return this.value === other.value;
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}
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toString(): string {
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return this.value;
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}
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}
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```
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**Example: Entity**
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```typescript
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// domain/entities/user.entity.ts
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import type { Email } from "@/domain/value-objects/email.value-object";
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export class User {
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private _isActive: boolean = true;
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private readonly _createdAt: Date;
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constructor(
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private readonly _id: string, // UUIDv7 string generated by Bun.randomUUIDv7()
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private _email: Email,
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private _name: string,
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private _hashedPassword: string
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) {
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this._createdAt = new Date();
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}
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// Domain behavior
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deactivate(): void {
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if (!this._isActive) {
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throw new Error(`User ${this._id} is already inactive`);
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}
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this._isActive = false;
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}
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changeEmail(newEmail: Email): void {
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if (this._email.equals(newEmail)) {
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return;
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}
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this._email = newEmail;
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}
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// Getters (no setters - controlled behavior)
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get id(): string {
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return this._id;
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}
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get email(): Email {
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return this._email;
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}
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get name(): string {
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return this._name;
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}
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get isActive(): boolean {
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return this._isActive;
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}
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get createdAt(): Date {
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return this._createdAt;
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}
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}
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```
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**Example: Port (Interface)**
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```typescript
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// domain/ports/repositories/user.repository.ts
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import type { User } from "@/domain/entities/user.entity";
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import type { Result } from "@/domain/shared/result";
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// NO "I" prefix
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export interface UserRepository {
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findById(id: string): Promise<Result<User | null>>; // id is UUIDv7 string
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findByEmail(email: string): Promise<Result<User | null>>;
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save(user: User): Promise<Result<void>>;
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update(user: User): Promise<Result<void>>;
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delete(id: string): Promise<Result<void>>; // id is UUIDv7 string
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}
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```
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### 2. Application Layer (Use Cases)
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**Contains**: Use Cases, DTOs, Mappers
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**Example: Use Case**
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```typescript
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// application/use-cases/create-user.use-case.ts
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import type { UserRepository } from "@/domain/ports";
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import type { CacheService } from "@/domain/ports";
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import type { Logger } from "@/domain/ports";
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import { User } from "@/domain/entities";
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import { Email } from "@/domain/value-objects";
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import type { CreateUserDto, UserResponseDto } from "@/application/dtos";
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export class CreateUserUseCase {
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constructor(
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private readonly userRepository: UserRepository,
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private readonly cacheService: CacheService,
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private readonly logger: Logger
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) {}
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async execute(dto: CreateUserDto): Promise<UserResponseDto> {
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this.logger.info("Creating user", { email: dto.email });
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// 1. Validate business rules
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const existingUser = await this.userRepository.findByEmail(dto.email);
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if (existingUser.isSuccess && existingUser.value) {
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throw new Error(`User with email ${dto.email} already exists`);
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}
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// 2. Create domain objects
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const id = Bun.randomUUIDv7(); // Generate UUIDv7 using Bun native API
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const email = Email.create(dto.email);
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const user = new User(id, email, dto.name, dto.hashedPassword);
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// 3. Persist
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const saveResult = await this.userRepository.save(user);
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if (saveResult.isFailure) {
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throw new Error(`Failed to save user: ${saveResult.error}`);
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}
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// 4. Invalidate cache
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await this.cacheService.del(`user:${email.toString()}`);
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// 5. Return DTO
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return {
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id: user.id.toString(),
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email: user.email.toString(),
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name: user.name,
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isActive: user.isActive,
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createdAt: user.createdAt.toISOString(),
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};
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}
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}
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```
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**Example: DTO**
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```typescript
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// application/dtos/user.dto.ts
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import { z } from "zod";
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export const createUserSchema = z.object({
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email: z.string().email(),
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password: z.string().min(8),
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name: z.string().min(2).max(100),
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});
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export type CreateUserDto = z.infer<typeof createUserSchema>;
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export interface UserResponseDto {
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id: string;
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email: string;
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name: string;
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isActive: boolean;
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createdAt: string;
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}
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```
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### 3. Infrastructure Layer (Technical Implementation)
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**Contains**: Repositories (database), Adapters (external services), Container (DI)
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**Example: Repository Implementation**
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```typescript
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// infrastructure/repositories/user.repository.impl.ts
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import { eq } from "drizzle-orm";
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import type { DatabaseConnection } from "@gesttione-solutions/neptunus";
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import type { UserRepository } from "@/domain/ports/repositories/user.repository";
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import type { User } from "@/domain/entities/user.entity";
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import { Result } from "@/domain/shared/result";
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import { users } from "@/infrastructure/database/drizzle/schema/users.schema";
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export class UserRepositoryImpl implements UserRepository {
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constructor(private readonly db: DatabaseConnection) {}
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async findById(id: string): Promise<Result<User | null>> {
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// id is UUIDv7 string
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try {
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const [row] = await this.db
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.select()
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.from(users)
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.where(eq(users.id, id))
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.limit(1);
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if (!row) {
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return Result.ok(null);
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}
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return Result.ok(this.toDomain(row));
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} catch (error) {
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return Result.fail(`Failed to find user: ${error}`);
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}
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}
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async save(user: User): Promise<Result<void>> {
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try {
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await this.db.insert(users).values({
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id: user.id, // UUIDv7 string
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email: user.email.toString(),
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name: user.name,
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isActive: user.isActive,
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createdAt: user.createdAt,
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});
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return Result.ok(undefined);
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} catch (error) {
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return Result.fail(`Failed to save user: ${error}`);
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}
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}
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private toDomain(row: typeof users.$inferSelect): User {
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// Reconstruct domain entity from database row
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const id = row.id; // UUIDv7 string from database
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const email = Email.create(row.email);
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return new User(id, email, row.name, row.hashedPassword);
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}
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}
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```
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**Example: Adapter (External Service)**
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```typescript
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// infrastructure/adapters/cache.service.impl.ts
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import { Redis } from "ioredis";
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import type { CacheService } from "@/domain/ports/cache.service";
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import type { EnvConfig } from "@/domain/ports/env-config.port";
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export class CacheServiceImpl implements CacheService {
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private redis: Redis;
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constructor(config: EnvConfig) {
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this.redis = new Redis({
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host: config.REDIS_HOST,
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port: config.REDIS_PORT,
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});
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}
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async set(
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key: string,
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value: string,
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expirationInSeconds?: number
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): Promise<void> {
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if (expirationInSeconds) {
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await this.redis.set(key, value, "EX", expirationInSeconds);
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} else {
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await this.redis.set(key, value);
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}
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}
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async get(key: string): Promise<string | null> {
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return await this.redis.get(key);
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}
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async del(key: string): Promise<void> {
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await this.redis.del(key);
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}
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async flushAll(): Promise<void> {
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await this.redis.flushall();
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}
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}
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```
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### 4. HTTP Layer (Framework-Specific, in Infrastructure)
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**Location**: `infrastructure/http/`
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**Contains**: Server, Controllers (self-registering), Schemas (Zod validation), Middleware, Plugins
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**Example: Schema**
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```typescript
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// infrastructure/http/schemas/user.schema.ts
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import { z } from "zod";
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export const createUserRequestSchema = z.object({
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email: z.string().email(),
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password: z.string().min(8),
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name: z.string().min(2).max(100),
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});
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export const userResponseSchema = z.object({
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id: z.string().uuid(),
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email: z.string().email(),
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name: z.string(),
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isActive: z.boolean(),
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createdAt: z.string().datetime(),
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});
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```
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**Example: Self-Registering Controller**
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```typescript
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// infrastructure/http/controllers/user.controller.ts
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import type { HttpServer } from "@/domain/ports/http-server";
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import { HttpMethod } from "@/domain/ports/http-server";
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import type { CreateUserUseCase } from "@/application/use-cases/create-user.use-case";
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import type { GetUserUseCase } from "@/application/use-cases/get-user.use-case";
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/**
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* UserController
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*
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* Infrastructure layer (HTTP) - handles HTTP requests.
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* Thin layer that delegates to use cases.
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*
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* Responsibilities:
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* 1. Register routes in constructor
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* 2. Validate requests (Zod schemas)
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* 3. Delegate to use cases
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* 4. Format responses (return DTOs)
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*
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* NO business logic here! Controllers should be thin.
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*
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* Pattern: Constructor Injection + Auto-registration
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*/
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export class UserController {
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constructor(
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private readonly httpServer: HttpServer, // ✅ HttpServer port injected
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private readonly createUserUseCase: CreateUserUseCase, // ✅ Use case injected
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private readonly getUserUseCase: GetUserUseCase // ✅ Use case injected
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) {
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this.registerRoutes(); // ✅ Auto-register routes in constructor
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}
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private registerRoutes(): void {
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// POST /users - Create new user
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this.httpServer.route(HttpMethod.POST, "/users", async (context) => {
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try {
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const dto = context.req.valid("json"); // Validated by middleware
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const user = await this.createUserUseCase.execute(dto);
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return context.json(user, 201);
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} catch (error) {
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console.error("Error creating user:", error);
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return context.json({ error: "Internal server error" }, 500);
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}
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});
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// GET /users/:id - Get user by ID
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this.httpServer.route(HttpMethod.GET, "/users/:id", async (context) => {
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try {
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const { id } = context.req.param();
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const user = await this.getUserUseCase.execute(id);
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return context.json(user, 200);
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} catch (error) {
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console.error("Error getting user:", error);
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return context.json({ error: "User not found" }, 404);
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}
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||||
});
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||||
}
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||||
}
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```
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**Example: HttpServer Port (Domain Layer)**
|
||||
|
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```typescript
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// domain/ports/http-server.ts
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export enum HttpMethod {
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GET = "GET",
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||||
POST = "POST",
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||||
PUT = "PUT",
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||||
DELETE = "DELETE",
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||||
PATCH = "PATCH",
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||||
}
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||||
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||||
export type HttpHandler = (context: unknown) => Promise<Response | unknown>;
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||||
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||||
export interface HttpServer {
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route(method: HttpMethod, url: string, handler: HttpHandler): void;
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||||
listen(port: number): void;
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||||
}
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||||
```
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||||
|
||||
**Example: HonoHttpServer Implementation (Infrastructure Layer)**
|
||||
|
||||
```typescript
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// infrastructure/http/server/hono-http-server.adapter.ts
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import type { Context } from "hono";
|
||||
import { Hono } from "hono";
|
||||
import {
|
||||
type HttpHandler,
|
||||
HttpMethod,
|
||||
type HttpServer,
|
||||
} from "@/domain/ports/http-server";
|
||||
|
||||
export class HonoHttpServer implements HttpServer {
|
||||
private readonly app: Hono;
|
||||
|
||||
constructor() {
|
||||
this.app = new Hono();
|
||||
}
|
||||
|
||||
route(method: HttpMethod, url: string, handler: HttpHandler): void {
|
||||
const honoHandler = async (c: Context) => {
|
||||
try {
|
||||
const result = await handler(c);
|
||||
return result instanceof Response ? result : (result as Response);
|
||||
} catch (error) {
|
||||
console.error("Error handling request:", error);
|
||||
return c.json({ error: "Internal server error" }, 500);
|
||||
}
|
||||
};
|
||||
|
||||
switch (method) {
|
||||
case HttpMethod.GET:
|
||||
this.app.get(url, honoHandler);
|
||||
break;
|
||||
case HttpMethod.POST:
|
||||
this.app.post(url, honoHandler);
|
||||
break;
|
||||
case HttpMethod.PUT:
|
||||
this.app.put(url, honoHandler);
|
||||
break;
|
||||
case HttpMethod.DELETE:
|
||||
this.app.delete(url, honoHandler);
|
||||
break;
|
||||
case HttpMethod.PATCH:
|
||||
this.app.patch(url, honoHandler);
|
||||
break;
|
||||
default:
|
||||
throw new Error(`Unsupported HTTP method: ${method}`);
|
||||
}
|
||||
}
|
||||
|
||||
listen(port: number): void {
|
||||
console.log(`Server is running on http://localhost:${port}`);
|
||||
Bun.serve({
|
||||
fetch: this.app.fetch,
|
||||
port,
|
||||
});
|
||||
}
|
||||
|
||||
getApp(): Hono {
|
||||
return this.app;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Example: Bootstrap (Entry Point)**
|
||||
|
||||
```typescript
|
||||
// main.ts
|
||||
import { getAppContainer, TOKENS } from "@/infrastructure/di";
|
||||
|
||||
const DEFAULT_PORT = 3000;
|
||||
|
||||
/**
|
||||
* Application Bootstrap
|
||||
*
|
||||
* 1. Get application container (DI)
|
||||
* 2. Initialize controllers (they auto-register routes in constructor)
|
||||
* 3. Start HTTP server
|
||||
*/
|
||||
async function bootstrap() {
|
||||
// Get application container (singleton)
|
||||
const container = getAppContainer();
|
||||
|
||||
// Initialize controllers (they auto-register routes in constructor)
|
||||
container.resolve(TOKENS.systemController);
|
||||
container.resolve(TOKENS.userController);
|
||||
|
||||
// Resolve and start HTTP server
|
||||
const server = container.resolve(TOKENS.httpServer);
|
||||
const port = Number(process.env.PORT) || DEFAULT_PORT;
|
||||
|
||||
server.listen(port);
|
||||
}
|
||||
|
||||
// Entry point with error handling
|
||||
bootstrap().catch((error) => {
|
||||
console.error("Failed to start server:", error);
|
||||
process.exit(1);
|
||||
});
|
||||
```
|
||||
|
||||
**Key Benefits:**
|
||||
|
||||
- ✅ **Thin controllers** - Only route registration + delegation
|
||||
- ✅ **Auto-registration** - Controllers register themselves in constructor
|
||||
- ✅ **Framework-agnostic domain** - HttpServer port in domain layer
|
||||
- ✅ **Testable** - Easy to mock HttpServer for testing controllers
|
||||
- ✅ **DI-friendly** - Controllers resolve via container
|
||||
- ✅ **Clean separation** - No routes/ folder needed
|
||||
- ✅ **Single responsibility** - Controllers only handle HTTP, business logic in use cases
|
||||
|
||||
## Dependency Injection Container
|
||||
|
||||
### Container Implementation
|
||||
|
||||
```typescript
|
||||
// infrastructure/container/container.ts
|
||||
export type Lifetime = "singleton" | "scoped" | "transient";
|
||||
export type Token<T> = symbol & { readonly __type?: T };
|
||||
|
||||
export interface Provider<T> {
|
||||
lifetime: Lifetime;
|
||||
useValue?: T;
|
||||
useFactory?: (c: Container) => T;
|
||||
}
|
||||
|
||||
export class Container {
|
||||
private readonly registry: Map<Token<unknown>, Provider<unknown>>;
|
||||
private readonly singletons: Map<Token<unknown>, unknown>;
|
||||
private readonly scopedCache: Map<Token<unknown>, unknown>;
|
||||
|
||||
private constructor(
|
||||
registry: Map<Token<unknown>, Provider<unknown>>,
|
||||
singletons: Map<Token<unknown>, unknown>,
|
||||
scopedCache?: Map<Token<unknown>, unknown>
|
||||
) {
|
||||
this.registry = registry;
|
||||
this.singletons = singletons;
|
||||
this.scopedCache = scopedCache ?? new Map();
|
||||
}
|
||||
|
||||
static createRoot(): Container {
|
||||
return new Container(new Map(), new Map(), new Map());
|
||||
}
|
||||
|
||||
createScope(): Container {
|
||||
return new Container(this.registry, this.singletons, new Map());
|
||||
}
|
||||
|
||||
register<T>(token: Token<T>, provider: Provider<T>): void {
|
||||
if (this.registry.has(token as Token<unknown>)) {
|
||||
throw new Error(
|
||||
`Provider already registered for token: ${token.description}`
|
||||
);
|
||||
}
|
||||
this.registry.set(token as Token<unknown>, provider as Provider<unknown>);
|
||||
}
|
||||
|
||||
resolve<T>(token: Token<T>): T {
|
||||
const provider = this.registry.get(token as Token<unknown>);
|
||||
if (!provider) {
|
||||
throw new Error(`No provider registered for token: ${token.description}`);
|
||||
}
|
||||
|
||||
// useValue
|
||||
if ("useValue" in provider && provider.useValue !== undefined) {
|
||||
return provider.useValue as T;
|
||||
}
|
||||
|
||||
// singleton cache
|
||||
if (provider.lifetime === "singleton") {
|
||||
if (this.singletons.has(token as Token<unknown>)) {
|
||||
return this.singletons.get(token as Token<unknown>) as T;
|
||||
}
|
||||
const instance = (provider as Provider<T>).useFactory!(this);
|
||||
this.singletons.set(token as Token<unknown>, instance);
|
||||
return instance;
|
||||
}
|
||||
|
||||
// scoped cache
|
||||
if (provider.lifetime === "scoped") {
|
||||
if (this.scopedCache.has(token as Token<unknown>)) {
|
||||
return this.scopedCache.get(token as Token<unknown>) as T;
|
||||
}
|
||||
const instance = (provider as Provider<T>).useFactory!(this);
|
||||
this.scopedCache.set(token as Token<unknown>, instance);
|
||||
return instance;
|
||||
}
|
||||
|
||||
// transient
|
||||
return (provider as Provider<T>).useFactory!(this);
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Tokens Definition
|
||||
|
||||
```typescript
|
||||
// infrastructure/container/tokens.ts
|
||||
import type { UserRepository } from "@/domain/ports/repositories/user.repository";
|
||||
import type { CacheService } from "@/domain/ports/cache.service";
|
||||
import type { Logger } from "@/domain/ports/logger.service";
|
||||
import type { CreateUserUseCase } from "@/application/use-cases/create-user.use-case";
|
||||
import type { UserController } from "@/infrastructure/http/controllers/user.controller";
|
||||
|
||||
export const TOKENS = {
|
||||
// Core
|
||||
Logger: Symbol("Logger") as Token<Logger>,
|
||||
Config: Symbol("Config") as Token<EnvConfig>,
|
||||
DatabaseConnection: Symbol("DatabaseConnection") as Token<DatabaseConnection>,
|
||||
|
||||
// Repositories
|
||||
UserRepository: Symbol("UserRepository") as Token<UserRepository>,
|
||||
|
||||
// Services
|
||||
CacheService: Symbol("CacheService") as Token<CacheService>,
|
||||
|
||||
// Use Cases
|
||||
CreateUserUseCase: Symbol("CreateUserUseCase") as Token<CreateUserUseCase>,
|
||||
|
||||
// Controllers
|
||||
UserController: Symbol("UserController") as Token<UserController>,
|
||||
} as const;
|
||||
```
|
||||
|
||||
### Registration Functions
|
||||
|
||||
```typescript
|
||||
// infrastructure/container/registers/register.infrastructure.ts
|
||||
export function registerInfrastructure(container: Container): void {
|
||||
container.register(TOKENS.Logger, {
|
||||
lifetime: "singleton",
|
||||
useValue: logger,
|
||||
});
|
||||
|
||||
container.register(TOKENS.DatabaseConnection, {
|
||||
lifetime: "singleton",
|
||||
useValue: dbConnection,
|
||||
});
|
||||
|
||||
container.register(TOKENS.Config, {
|
||||
lifetime: "singleton",
|
||||
useValue: Config.getInstance().env,
|
||||
});
|
||||
}
|
||||
|
||||
// infrastructure/container/registers/register.repositories.ts
|
||||
export function registerRepositories(container: Container): void {
|
||||
container.register(TOKENS.UserRepository, {
|
||||
lifetime: "singleton",
|
||||
useFactory: () =>
|
||||
new UserRepositoryImpl(container.resolve(TOKENS.DatabaseConnection)),
|
||||
});
|
||||
}
|
||||
|
||||
// infrastructure/container/registers/register.use-cases.ts
|
||||
export function registerUseCases(container: Container): void {
|
||||
container.register(TOKENS.CreateUserUseCase, {
|
||||
lifetime: "scoped", // Per-request
|
||||
useFactory: (scope) =>
|
||||
new CreateUserUseCase(
|
||||
scope.resolve(TOKENS.UserRepository),
|
||||
scope.resolve(TOKENS.CacheService),
|
||||
scope.resolve(TOKENS.Logger)
|
||||
),
|
||||
});
|
||||
}
|
||||
|
||||
// infrastructure/container/registers/register.controllers.ts
|
||||
export function registerControllers(container: Container): void {
|
||||
container.register(TOKENS.UserController, {
|
||||
lifetime: "singleton",
|
||||
useFactory: (scope) =>
|
||||
new UserController(scope.resolve(TOKENS.CreateUserUseCase)),
|
||||
});
|
||||
}
|
||||
```
|
||||
|
||||
### Composition Root
|
||||
|
||||
```typescript
|
||||
// infrastructure/container/main.ts
|
||||
export function createRootContainer(): Container {
|
||||
const c = Container.createRoot();
|
||||
|
||||
registerInfrastructure(c);
|
||||
registerRepositories(c);
|
||||
registerUseCases(c);
|
||||
registerControllers(c);
|
||||
|
||||
return c;
|
||||
}
|
||||
|
||||
let rootContainer: Container | null = null;
|
||||
|
||||
export function getAppContainer(): Container {
|
||||
if (!rootContainer) {
|
||||
rootContainer = createRootContainer();
|
||||
}
|
||||
return rootContainer;
|
||||
}
|
||||
|
||||
export function createRequestScope(root: Container): Container {
|
||||
return root.createScope();
|
||||
}
|
||||
```
|
||||
|
||||
### Usage in Hono App
|
||||
|
||||
```typescript
|
||||
// infrastructure/http/app.ts
|
||||
import { Hono } from "hono";
|
||||
import {
|
||||
getAppContainer,
|
||||
createRequestScope,
|
||||
} from "@/infrastructure/container/main";
|
||||
import { TOKENS } from "@/infrastructure/container/tokens";
|
||||
// Note: With self-registering controllers, route registration is handled by controllers themselves
|
||||
|
||||
const app = new Hono();
|
||||
|
||||
// Middleware: Create scoped container per request
|
||||
app.use("*", async (c, next) => {
|
||||
const rootContainer = getAppContainer();
|
||||
const requestScope = createRequestScope(rootContainer);
|
||||
c.set("container", requestScope);
|
||||
await next();
|
||||
});
|
||||
|
||||
// Register routes
|
||||
const userController = app.get("container").resolve(TOKENS.UserController);
|
||||
registerUserRoutes(app, userController);
|
||||
|
||||
export default app;
|
||||
```
|
||||
|
||||
## Best Practices
|
||||
|
||||
### ✅ Do:
|
||||
|
||||
- **Keep domain layer pure** - No external dependencies
|
||||
- **Use interfaces (ports)** - All external dependencies behind ports
|
||||
- **Rich domain models** - Entities with behavior, not just data
|
||||
- **Use cases orchestrate** - Don't put business logic in controllers
|
||||
- **Inject dependencies** - Constructor injection via DI container
|
||||
- **Symbol-based tokens** - Type-safe DI tokens
|
||||
- **Scoped use cases** - Per-request instances
|
||||
- **Singleton repositories** - Stateless, thread-safe
|
||||
- **Result type** - For expected failures (not exceptions)
|
||||
|
||||
### ❌ Don't:
|
||||
|
||||
- **Anemic domain models** - Entities shouldn't be just data bags
|
||||
- **Business logic in controllers** - Controllers should be thin
|
||||
- **Domain depending on infrastructure** - Breaks dependency rule
|
||||
- **Skip interfaces** - Always use ports for external dependencies
|
||||
- **Use concrete implementations in use cases** - Depend on abstractions
|
||||
- **Manual DI** - Use the container
|
||||
- **External DI libraries** - Use custom container (InversifyJS, TSyringe)
|
||||
|
||||
## Common Patterns
|
||||
|
||||
**For complete error handling patterns (Result/Either types, Exception Hierarchy, Retry Logic, Circuit Breaker, Validation Strategies), see `error-handling-patterns` skill**
|
||||
|
||||
### Domain Events
|
||||
|
||||
```typescript
|
||||
// domain/events/user-created.event.ts
|
||||
export class UserCreatedEvent {
|
||||
constructor(
|
||||
public readonly userId: string,
|
||||
public readonly email: string,
|
||||
public readonly occurredAt: Date = new Date()
|
||||
) {}
|
||||
}
|
||||
|
||||
// In Use Case
|
||||
async execute(dto: CreateUserDto): Promise<UserResponseDto> {
|
||||
// ... create user ...
|
||||
await this.eventBus.publish(new UserCreatedEvent(user.id.toString(), user.email.toString()));
|
||||
return response;
|
||||
}
|
||||
```
|
||||
|
||||
## Remember
|
||||
|
||||
- **Clean Architecture is about maintainability**, not perfection
|
||||
- **The Dependency Rule is sacred** - Always point inward
|
||||
- **Domain is the core** - Everything revolves around it
|
||||
- **Test domain first** - It's the most important part
|
||||
- **Use custom DI container** - No external libraries
|
||||
- **Symbol-based tokens** - Type-safe dependency injection
|
||||
- **Scoped lifetimes for use cases** - Per-request isolation
|
||||
Reference in New Issue
Block a user