API Design

API 设计模式

用于设计一致、对开发者友好的 REST API 的约定和最佳实践。

何时启用

• 设计新的 API 端点时
• 审查现有的 API 契约时
• 添加分页、过滤或排序功能时
• 为 API 实现错误处理时
• 规划 API 版本策略时
• 构建面向公众或合作伙伴的 API 时

资源设计

URL 结构

# Resources are nouns, plural, lowercase, kebab-case
GET    /api/v1/users
GET    /api/v1/users/:id
POST   /api/v1/users
PUT    /api/v1/users/:id
PATCH  /api/v1/users/:id
DELETE /api/v1/users/:id

# Sub-resources for relationships
GET    /api/v1/users/:id/orders
POST   /api/v1/users/:id/orders

# Actions that don't map to CRUD (use verbs sparingly)
POST   /api/v1/orders/:id/cancel
POST   /api/v1/auth/login
POST   /api/v1/auth/refresh

命名规则

# GOOD
/api/v1/team-members          # kebab-case for multi-word resources
/api/v1/orders?status=active  # query params for filtering
/api/v1/users/123/orders      # nested resources for ownership

# BAD
/api/v1/getUsers              # verb in URL
/api/v1/user                  # singular (use plural)
/api/v1/team_members          # snake_case in URLs
/api/v1/users/123/getOrders   # verb in nested resource

HTTP 方法和状态码

方法语义

*通过适当的实现，PATCH 可以实现幂等

状态码参考

# Success
200 OK                    — GET, PUT, PATCH (with response body)
201 Created               — POST (include Location header)
204 No Content            — DELETE, PUT (no response body)

# Client Errors
400 Bad Request           — Validation failure, malformed JSON
401 Unauthorized          — Missing or invalid authentication
403 Forbidden             — Authenticated but not authorized
404 Not Found             — Resource doesn't exist
409 Conflict              — Duplicate entry, state conflict
422 Unprocessable Entity  — Semantically invalid (valid JSON, bad data)
429 Too Many Requests     — Rate limit exceeded

# Server Errors
500 Internal Server Error — Unexpected failure (never expose details)
502 Bad Gateway           — Upstream service failed
503 Service Unavailable   — Temporary overload, include Retry-After

常见错误

# BAD: 200 for everything
{ "status": 200, "success": false, "error": "Not found" }

# GOOD: Use HTTP status codes semantically
HTTP/1.1 404 Not Found
{ "error": { "code": "not_found", "message": "User not found" } }

# BAD: 500 for validation errors
# GOOD: 400 or 422 with field-level details

# BAD: 200 for created resources
# GOOD: 201 with Location header
HTTP/1.1 201 Created
Location: /api/v1/users/abc-123

响应格式

成功响应

{
  "data": {
    "id": "abc-123",
    "email": "alice@example.com",
    "name": "Alice",
    "created_at": "2025-01-15T10:30:00Z"
  }
}

集合响应（带分页）

{
  "data": [
    { "id": "abc-123", "name": "Alice" },
    { "id": "def-456", "name": "Bob" }
  ],
  "meta": {
    "total": 142,
    "page": 1,
    "per_page": 20,
    "total_pages": 8
  },
  "links": {
    "self": "/api/v1/users?page=1&per_page=20",
    "next": "/api/v1/users?page=2&per_page=20",
    "last": "/api/v1/users?page=8&per_page=20"
  }
}

错误响应

{
  "error": {
    "code": "validation_error",
    "message": "Request validation failed",
    "details": [
      {
        "field": "email",
        "message": "Must be a valid email address",
        "code": "invalid_format"
      },
      {
        "field": "age",
        "message": "Must be between 0 and 150",
        "code": "out_of_range"
      }
    ]
  }
}

响应包装器变体

// Option A: Envelope with data wrapper (recommended for public APIs)
interface ApiResponse<T> {
  data: T;
  meta?: PaginationMeta;
  links?: PaginationLinks;
}

interface ApiError {
  error: {
    code: string;
    message: string;
    details?: FieldError[];
  };
}

// Option B: Flat response (simpler, common for internal APIs)
// Success: just return the resource directly
// Error: return error object
// Distinguish by HTTP status code

分页

基于偏移量（简单）

GET /api/v1/users?page=2&per_page=20

# Implementation
SELECT * FROM users
ORDER BY created_at DESC
LIMIT 20 OFFSET 20;

优点： 易于实现，支持“跳转到第 N 页” 缺点： 在大偏移量时速度慢（例如 OFFSET 100000），并发插入时结果不一致

基于游标（可扩展）

GET /api/v1/users?cursor=eyJpZCI6MTIzfQ&limit=20

# Implementation
SELECT * FROM users
WHERE id > :cursor_id
ORDER BY id ASC
LIMIT 21;  -- fetch one extra to determine has_next

{
  "data": [...],
  "meta": {
    "has_next": true,
    "next_cursor": "eyJpZCI6MTQzfQ"
  }
}

优点： 无论位置如何，性能一致；在并发插入时结果稳定 缺点： 无法跳转到任意页面；游标是不透明的

何时使用哪种

过滤、排序和搜索

过滤

# Simple equality
GET /api/v1/orders?status=active&customer_id=abc-123

# Comparison operators (use bracket notation)
GET /api/v1/products?price[gte]=10&price[lte]=100
GET /api/v1/orders?created_at[after]=2025-01-01

# Multiple values (comma-separated)
GET /api/v1/products?category=electronics,clothing

# Nested fields (dot notation)
GET /api/v1/orders?customer.country=US

排序

# Single field (prefix - for descending)
GET /api/v1/products?sort=-created_at

# Multiple fields (comma-separated)
GET /api/v1/products?sort=-featured,price,-created_at

全文搜索

# Search query parameter
GET /api/v1/products?q=wireless+headphones

# Field-specific search
GET /api/v1/users?email=alice

稀疏字段集

# Return only specified fields (reduces payload)
GET /api/v1/users?fields=id,name,email
GET /api/v1/orders?fields=id,total,status&include=customer.name

认证和授权

基于令牌的认证

# Bearer token in Authorization header
GET /api/v1/users
Authorization: Bearer eyJhbGciOiJIUzI1NiIs...

# API key (for server-to-server)
GET /api/v1/data
X-API-Key: sk_live_abc123

授权模式

// Resource-level: check ownership
app.get("/api/v1/orders/:id", async (req, res) => {
  const order = await Order.findById(req.params.id);
  if (!order) return res.status(404).json({ error: { code: "not_found" } });
  if (order.userId !== req.user.id) return res.status(403).json({ error: { code: "forbidden" } });
  return res.json({ data: order });
});

// Role-based: check permissions
app.delete("/api/v1/users/:id", requireRole("admin"), async (req, res) => {
  await User.delete(req.params.id);
  return res.status(204).send();
});

速率限制

响应头

HTTP/1.1 200 OK
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1640000000

# When exceeded
HTTP/1.1 429 Too Many Requests
Retry-After: 60
{
  "error": {
    "code": "rate_limit_exceeded",
    "message": "Rate limit exceeded. Try again in 60 seconds."
  }
}

速率限制层级

版本控制

URL 路径版本控制（推荐）

/api/v1/users
/api/v2/users

优点： 明确，易于路由，可缓存 缺点： 版本间 URL 会变化

请求头版本控制

GET /api/users
Accept: application/vnd.myapp.v2+json

优点： URL 简洁 缺点： 测试更困难，容易忘记

版本控制策略

1. Start with /api/v1/ — don't version until you need to
2. Maintain at most 2 active versions (current + previous)
3. Deprecation timeline:
   - Announce deprecation (6 months notice for public APIs)
   - Add Sunset header: Sunset: Sat, 01 Jan 2026 00:00:00 GMT
   - Return 410 Gone after sunset date
4. Non-breaking changes don't need a new version:
   - Adding new fields to responses
   - Adding new optional query parameters
   - Adding new endpoints
5. Breaking changes require a new version:
   - Removing or renaming fields
   - Changing field types
   - Changing URL structure
   - Changing authentication method

实现模式

TypeScript (Next.js API 路由)

import { z } from "zod";
import { NextRequest, NextResponse } from "next/server";

const createUserSchema = z.object({
  email: z.string().email(),
  name: z.string().min(1).max(100),
});

export async function POST(req: NextRequest) {
  const body = await req.json();
  const parsed = createUserSchema.safeParse(body);

  if (!parsed.success) {
    return NextResponse.json({
      error: {
        code: "validation_error",
        message: "Request validation failed",
        details: parsed.error.issues.map(i => ({
          field: i.path.join("."),
          message: i.message,
          code: i.code,
        })),
      },
    }, { status: 422 });
  }

  const user = await createUser(parsed.data);

  return NextResponse.json(
    { data: user },
    {
      status: 201,
      headers: { Location: `/api/v1/users/${user.id}` },
    },
  );
}

Python (Django REST Framework)

from rest_framework import serializers, viewsets, status
from rest_framework.response import Response

class CreateUserSerializer(serializers.Serializer):
    email = serializers.EmailField()
    name = serializers.CharField(max_length=100)

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ["id", "email", "name", "created_at"]

class UserViewSet(viewsets.ModelViewSet):
    serializer_class = UserSerializer
    permission_classes = [IsAuthenticated]

    def get_serializer_class(self):
        if self.action == "create":
            return CreateUserSerializer
        return UserSerializer

    def create(self, request):
        serializer = CreateUserSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        user = UserService.create(**serializer.validated_data)
        return Response(
            {"data": UserSerializer(user).data},
            status=status.HTTP_201_CREATED,
            headers={"Location": f"/api/v1/users/{user.id}"},
        )

Go (net/http)

func (h *UserHandler) CreateUser(w http.ResponseWriter, r *http.Request) {
    var req CreateUserRequest
    if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
        writeError(w, http.StatusBadRequest, "invalid_json", "Invalid request body")
        return
    }

    if err := req.Validate(); err != nil {
        writeError(w, http.StatusUnprocessableEntity, "validation_error", err.Error())
        return
    }

    user, err := h.service.Create(r.Context(), req)
    if err != nil {
        switch {
        case errors.Is(err, domain.ErrEmailTaken):
            writeError(w, http.StatusConflict, "email_taken", "Email already registered")
        default:
            writeError(w, http.StatusInternalServerError, "internal_error", "Internal error")
        }
        return
    }

    w.Header().Set("Location", fmt.Sprintf("/api/v1/users/%s", user.ID))
    writeJSON(w, http.StatusCreated, map[string]any{"data": user})
}

API 设计清单

发布新端点前请检查：

• [ ] 资源 URL 遵循命名约定（复数、短横线连接、不含动词）
• [ ] 使用了正确的 HTTP 方法（GET 用于读取，POST 用于创建等）
• [ ] 返回了适当的状态码（不要所有情况都返回 200）
• [ ] 使用模式（Zod, Pydantic, Bean Validation）验证了输入
• [ ] 错误响应遵循带代码和消息的标准格式
• [ ] 列表端点实现了分页（游标或偏移量）
• [ ] 需要认证（或明确标记为公开）
• [ ] 检查了授权（用户只能访问自己的资源）
• [ ] 配置了速率限制
• [ ] 响应未泄露内部细节（堆栈跟踪、SQL 错误）
• [ ] 与现有端点命名一致（camelCase 对比 snake_case）
• [ ] 已记录（更新了 OpenAPI/Swagger 规范）