domain-web

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Original

English

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Translation

Chinese

Web Domain

Web 领域

Layer 3: Domain Constraints

第3层：领域约束

Domain Constraints → Design Implications

领域约束 → 设计影响

Domain Rule	Design Constraint	Rust Implication
Stateless HTTP	No request-local globals	State in extractors
Concurrency	Handle many connections	Async, Send + Sync
Latency SLA	Fast response	Efficient ownership
Security	Input validation	Type-safe extractors
Observability	Request tracing	tracing + tower layers

领域规则	设计约束	Rust 实现方案
无状态HTTP	无请求本地全局变量	使用提取器管理状态
并发处理	处理大量连接	异步编程、Send + Sync
延迟SLA	快速响应	高效所有权管理
安全性	输入验证	类型安全的提取器
可观测性	请求追踪	tracing + tower 层

Critical Constraints

关键约束

Async by Default

默认异步

RULE: Web handlers must not block
WHY: Block one task = block many requests
RUST: async/await, spawn_blocking for CPU work

RULE: Web handlers must not block
WHY: Block one task = block many requests
RUST: async/await, spawn_blocking for CPU work

State Management

状态管理

RULE: Shared state must be thread-safe
WHY: Handlers run on any thread
RUST: Arc<T>, Arc<RwLock<T>> for mutable

RULE: Shared state must be thread-safe
WHY: Handlers run on any thread
RUST: Arc<T>, Arc<RwLock<T>> for mutable

Request Lifecycle

请求生命周期

RULE: Resources live only for request duration
WHY: Memory management, no leaks
RUST: Extractors, proper ownership

RULE: Resources live only for request duration
WHY: Memory management, no leaks
RUST: Extractors, proper ownership

Trace Down ↓

向下追溯 ↓

From constraints to design (Layer 2):

"Need shared application state"
    ↓ m07-concurrency: Use Arc for thread-safe sharing
    ↓ m02-resource: Arc<RwLock<T>> for mutable state

"Need request validation"
    ↓ m05-type-driven: Validated extractors
    ↓ m06-error-handling: IntoResponse for errors

"Need middleware stack"
    ↓ m12-lifecycle: Tower layers
    ↓ m04-zero-cost: Trait-based composition

从约束到设计（第2层）：

"Need shared application state"
    ↓ m07-concurrency: Use Arc for thread-safe sharing
    ↓ m02-resource: Arc<RwLock<T>> for mutable state

"Need request validation"
    ↓ m05-type-driven: Validated extractors
    ↓ m06-error-handling: IntoResponse for errors

"Need middleware stack"
    ↓ m12-lifecycle: Tower layers
    ↓ m04-zero-cost: Trait-based composition

Framework Comparison

框架对比

Framework	Style	Best For
axum	Functional, tower	Modern APIs
actix-web	Actor-based	High performance
warp	Filter composition	Composable APIs
rocket	Macro-driven	Rapid development

框架	风格	适用场景
axum	函数式、基于tower	现代API
actix-web	基于Actor模型	高性能场景
warp	过滤器组合	可组合API
rocket	宏驱动	快速开发

Key Crates

核心依赖库

Purpose	Crate
HTTP server	axum, actix-web
HTTP client	reqwest
JSON	serde_json
Auth/JWT	jsonwebtoken
Session	tower-sessions
Database	sqlx, diesel
Middleware	tower

用途	依赖库
HTTP服务器	axum, actix-web
HTTP客户端	reqwest
JSON处理	serde_json
身份验证/JWT	jsonwebtoken
会话管理	tower-sessions
数据库	sqlx, diesel
中间件	tower

Design Patterns

设计模式

Pattern	Purpose	Implementation
Extractors	Request parsing	`State(db)` , `Json(payload)`
Error response	Unified errors	`impl IntoResponse`
Middleware	Cross-cutting	Tower layers
Shared state	App config	`Arc<AppState>`

模式	用途	实现方式
提取器	请求解析	`State(db)` , `Json(payload)`
错误响应	统一错误处理	`impl IntoResponse`
中间件	横切关注点处理	Tower 层
共享状态	应用配置	`Arc<AppState>`

Code Pattern: Axum Handler

代码示例：Axum 处理器

rust

async fn handler(
    State(db): State<Arc<DbPool>>,
    Json(payload): Json<CreateUser>,
) -> Result<Json<User>, AppError> {
    let user = db.create_user(&payload).await?;
    Ok(Json(user))
}

// Error handling
impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        let (status, message) = match self {
            Self::NotFound => (StatusCode::NOT_FOUND, "Not found"),
            Self::Internal(_) => (StatusCode::INTERNAL_SERVER_ERROR, "Internal error"),
        };
        (status, Json(json!({"error": message}))).into_response()
    }
}

rust

async fn handler(
    State(db): State<Arc<DbPool>>,
    Json(payload): Json<CreateUser>,
) -> Result<Json<User>, AppError> {
    let user = db.create_user(&payload).await?;
    Ok(Json(user))
}

// Error handling
impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        let (status, message) = match self {
            Self::NotFound => (StatusCode::NOT_FOUND, "Not found"),
            Self::Internal(_) => (StatusCode::INTERNAL_SERVER_ERROR, "Internal error"),
        };
        (status, Json(json!({"error": message}))).into_response()
    }
}

Common Mistakes

常见错误

Mistake	Domain Violation	Fix
Blocking in handler	Latency spike	spawn_blocking
Rc in state	Not Send + Sync	Use Arc
No validation	Security risk	Type-safe extractors
No error response	Bad UX	IntoResponse impl

错误	违反的领域规则	修复方案
处理器中阻塞操作	延迟突增	使用spawn_blocking
状态中使用Rc	不满足Send + Sync	使用Arc
无输入验证	安全风险	使用类型安全的提取器
无统一错误响应	糟糕的用户体验	实现IntoResponse

Trace to Layer 1

追溯到第1层

Constraint	Layer 2 Pattern	Layer 1 Implementation
Async handlers	Async/await	tokio runtime
Thread-safe state	Shared state	Arc<T>, Arc<RwLock<T>>
Request lifecycle	Extractors	Ownership via From<Request>
Middleware	Tower layers	Trait-based composition

约束	第2层模式	第1层实现
异步处理器	Async/await	tokio 运行时
线程安全状态	共享状态	Arc<T>, Arc<RwLock<T>>
请求生命周期	提取器	通过From<Request>实现所有权管理
中间件	Tower 层	基于 trait 的组合

domain-web

Original

Translation

Web Domain

Web 领域

Domain Constraints → Design Implications

领域约束 → 设计影响

Critical Constraints

关键约束

Async by Default

默认异步

State Management

状态管理

Request Lifecycle

请求生命周期

Trace Down ↓

向下追溯 ↓

Framework Comparison

框架对比

Key Crates

核心依赖库

Design Patterns

设计模式

Code Pattern: Axum Handler

代码示例：Axum 处理器

Common Mistakes

常见错误

Trace to Layer 1

追溯到第1层

Related Skills

相关技能

When	See
Async patterns	m07-concurrency
State management	m02-resource
Error handling	m06-error-handling
Middleware design	m12-lifecycle

场景	参考内容
异步模式	m07-concurrency
状态管理	m02-resource
错误处理	m06-error-handling
中间件设计	m12-lifecycle