app.use(async (ctx) => {  // 请求方法  ctx.method;          // 'GET' / 'POST' / ...  ctx.path;            // '/users/123'  ctx.url;             // '/users/123?name=alice'    // 请求头  ctx.header;          // 所有请求头对象  ctx.get('Authorization');  // 获取单个请求头（推荐）  ctx.headers.host;    // 直接访问    // 查询参数  ctx.query;           // { name: 'alice', age: '25' }  ctx.querystring;     // 'name=alice&age=25'    // 路径参数（需配合路由中间件）  ctx.params;          // { id: '123' }    // 请求体（需配合 koa-bodyparser）  ctx.request.body;    // { username: 'alice', password: '123456' }    // IP  ctx.ip;              // 客户端 IP  ctx.ips;             // 代理链 IP 数组    // Cookie  ctx.cookies.get('name');     // 获取 Cookie  ctx.cookies.set('name', 'value', {    httpOnly: true,    maxAge: 7 * 24 * 3600 * 1000,  // 7 天  });});

app.use(async (ctx) => {  // 响应体（最常用）  ctx.body = 'Hello';              // 字符串  ctx.body = { code: 200, data: {} };  // JSON（自动设置 Content-Type）  ctx.body = Buffer.from('...');   // Buffer  ctx.body = fs.createReadStream('file.pdf');  // Stream    // 状态码  ctx.status = 200;   // OK  ctx.status = 404;   // Not Found  ctx.status = 500;   // Server Error    // 响应头  ctx.set('X-Custom-Header', 'value');  ctx.set({    'Cache-Control': 'no-cache',    'X-Total-Count': '100',  });    // 重定向  ctx.redirect('/login');  ctx.redirect('https://example.com');    // 附加数据（不会发送给客户端，中间件间传递）  ctx.state.user = { id: 1, name: 'Alice' };});

const Koa = require('koa');const app = new Koa();// 中间件 Aapp.use(async (ctx, next) => {  console.log('A - 请求前');  await next();  // 把控制权交给下一个中间件  console.log('A - 响应后');});// 中间件 Bapp.use(async (ctx, next) => {  console.log('B - 请求前');  await next();  console.log('B - 响应后');});// 中间件 C（实际处理）app.use(async (ctx) => {  console.log('C - 处理请求');  ctx.body = 'Hello';});// 输出顺序：// A - 请求前// B - 请求前// C - 处理请求// B - 响应后// A - 响应后

// 1. 日志中间件app.use(async (ctx, next) => {  const start = new Date();  await next();  const ms = new Date() - start;  console.log(`${ctx.method} ${ctx.url} ${ctx.status} - ${ms}ms`);});// 2. 统一响应格式app.use(async (ctx, next) => {  await next();  if (ctx.body && typeof ctx.body === 'object') {    ctx.body = {      code: ctx.status === 200 ? 0 : ctx.status,      message: ctx.message || 'success',      data: ctx.body,    };  }});// 3. CORS 跨域app.use(async (ctx, next) => {  ctx.set('Access-Control-Allow-Origin', '*');  ctx.set('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');  ctx.set('Access-Control-Allow-Headers', 'Content-Type, Authorization');  if (ctx.method === 'OPTIONS') {    ctx.status = 204;    return;  }  await next();});

const Koa = require('koa');const Router = require('@koa/router');const app = new Koa();const router = new Router();// GET 请求router.get('/', (ctx) => {  ctx.body = '首页';});router.get('/users', (ctx) => {  ctx.body = '用户列表';});// POST 请求（需配合 koa-bodyparser 荣获取 body）router.post('/users', (ctx) => {  const body = ctx.request.body;  ctx.body = { message: '创建成功', data: body };});// 动态路由router.get('/users/:id', (ctx) => {  const id = ctx.params.id;  ctx.body = `用户 ${id}`;});// PUT / DELETErouter.put('/users/:id', (ctx) => {  ctx.body = `更新用户 ${ctx.params.id}`;});router.delete('/users/:id', (ctx) => {  ctx.body = `删除用户 ${ctx.params.id}`;});// 使用路由app.use(router.routes());app.use(router.allowedMethods());  // 自动响应 OPTIONS，处理 405/501app.listen(3000);

// routes/user.routes.jsconst Router = require('@koa/router');const router = new Router({ prefix: '/users' });router.get('/', (ctx) => { ctx.body = '用户列表'; });router.get('/:id', (ctx) => { ctx.body = `用户 ${ctx.params.id}`; });router.post('/', (ctx) => { ctx.body = '创建用户'; });module.exports = router;// routes/order.routes.jsconst Router = require('@koa/router');const router = new Router({ prefix: '/orders' });router.get('/', (ctx) => { ctx.body = '订单列表'; });module.exports = router;// app.jsconst Koa = require('koa');const app = new Koa();const userRoutes = require('./routes/user.routes');const orderRoutes = require('./routes/order.routes');app.use(userRoutes.routes()).use(userRoutes.allowedMethods());app.use(orderRoutes.routes()).use(orderRoutes.allowedMethods());app.listen(3000);

// 安装 bodyparser// npm install koa-bodyparserconst bodyParser = require('koa-bodyparser');app.use(bodyParser());router.post('/users', (ctx) => {  // 1. 路径参数  // GET /users/123  ctx.params.id;  // '123'    // 2. 查询参数  // GET /users?page=1&size=10&keyword=alice  ctx.query.page;     // '1'  ctx.query.size;     // '10'  ctx.query.keyword;  // 'alice'    // 3. 请求体（需 koa-bodyparser）  // POST /users  Body: { "name": "Alice", "age": 25 }  ctx.request.body.name;  // 'Alice'  ctx.request.body.age;   // 25    // 4. 请求头  ctx.get('Authorization');  // 'Bearer xxx'  ctx.get('Content-Type');   // 'application/json'    // 5. 表单数据（application/x-www-form-urlencoded）  // koa-bodyparser 也支持  ctx.request.body.username;    ctx.body = { message: '参数获取成功' };});

const Koa = require('koa');const Router = require('@koa/router');const multer = require('@koa/multer');const path = require('path');const app = new Koa();const router = new Router();// 配置 multerconst storage = multer.diskStorage({  destination: (req, file, cb) => {    cb(null, 'uploads/');  },  filename: (req, file, cb) => {    const ext = path.extname(file.originalname);    const filename = `${Date.now()}-${Math.round(Math.random() * 1e9)}${ext}`;    cb(null, filename);  },});const upload = multer({  storage,  limits: { fileSize: 5 * 1024 * 1024 },  // 5MB  fileFilter: (req, file, cb) => {    const allowed = /jpeg|jpg|png|gif|webp/;    const ok = allowed.test(path.extname(file.originalname).toLowerCase());    if (ok) cb(null, true);    else cb(new Error('只支持图片格式'));  },});// 单文件上传router.post('/upload', upload.single('file'), (ctx) => {  const file = ctx.file;  ctx.body = {    url: `/uploads/${file.filename}`,    filename: file.filename,    size: file.size,  };});// 多文件上传router.post('/uploads', upload.array('files', 10), (ctx) => {  const files = ctx.files;  ctx.body = files.map(f => ({    url: `/uploads/${f.filename}`,    filename: f.filename,  }));});app.use(router.routes());app.listen(3000);

// Cookierouter.get('/set-cookie', (ctx) => {  ctx.cookies.set('name', 'Alice', {    httpOnly: true,           // JS 不可读    maxAge: 7 * 24 * 3600 * 1000,  // 7 天    sameSite: 'strict',    secure: false,            // 生产环境用 true（HTTPS）  });  ctx.body = 'Cookie 已设置';});router.get('/get-cookie', (ctx) => {  const name = ctx.cookies.get('name');  ctx.body = `Cookie: ${name}`;});// Session（需安装 koa-session）// npm install koa-sessionconst session = require('koa-session');app.keys = ['your-secret-key'];  // 必须设置app.use(session({  maxAge: 7 * 24 * 3600 * 1000,  httpOnly: true,}, app));router.post('/login', (ctx) => {  // 验证用户...  ctx.session.userId = 1;  ctx.session.username = 'Alice';  ctx.body = '登录成功';});router.get('/profile', (ctx) => {  if (!ctx.session.userId) {    ctx.status = 401;    ctx.body = '请先登录';    return;  }  ctx.body = { userId: ctx.session.userId, username: ctx.session.username };});router.post('/logout', (ctx) => {  ctx.session = null;  ctx.body = '已退出';});

const Koa = require('koa');const bodyParser = require('koa-bodyparser');const cors = require('koa2-cors');const logger = require('koa-logger');const helmet = require('koa-helmet');const compress = require('koa-compress');const app = new Koa();// 安全头app.use(helmet());// 请求日志app.use(logger());// Gzip 压缩app.use(compress({  threshold: 1024,  // 大于 1KB 才压缩}));// CORS 跨域app.use(cors({  origin: (ctx) => {    // 白名单    const allowedOrigins = ['https://example.com', 'http://localhost:5173'];    const origin = ctx.header.origin;    if (allowedOrigins.includes(origin)) {      return origin;    }    return null;  },  allowMethods: ['GET', 'POST', 'PUT', 'DELETE', 'OPTIONS'],  allowHeaders: ['Content-Type', 'Authorization'],  credentials: true,}));// 请求体解析app.use(bodyParser({  jsonLimit: '10mb',  formLimit: '10mb',  textLimit: '10mb',}));

// config/database.jsconst mysql = require('mysql2/promise');const pool = mysql.createPool({  host: 'localhost',  port: 3306,  user: 'root',  password: '123456',  database: 'travel_db',  waitForConnections: true,  connectionLimit: 10,  queueLimit: 0,});module.exports = pool;// services/user.service.jsconst pool = require('../config/database');class UserService {  async findAll(page = 1, size = 10) {    const offset = (page - 1) * size;    const [rows] = await pool.query(      'SELECT id, username, email, status FROM users ORDER BY id DESC LIMIT ? OFFSET ?',      [Number(size), Number(offset)]    );    const [[{ total }]] = await pool.query('SELECT COUNT(*) as total FROM users');    return { list: rows, total, page, size };  }  async findById(id) {    const [rows] = await pool.query('SELECT * FROM users WHERE id = ?', [id]);    return rows[0];  }  async create(data) {    const { username, email, password } = data;    const [result] = await pool.query(      'INSERT INTO users (username, email, password) VALUES (?, ?, ?)',      [username, email, password]    );    return { id: result.insertId, username, email };  }  async update(id, data) {    const fields = [];    const values = [];    for (const [key, value] of Object.entries(data)) {      fields.push(`${key} = ?`);      values.push(value);    }    values.push(id);    await pool.query(`UPDATE users SET ${fields.join(', ')} WHERE id = ?`, values);    return this.findById(id);  }  async delete(id) {    await pool.query('DELETE FROM users WHERE id = ?', [id]);  }}module.exports = new UserService();

// config/redis.jsconst Redis = require('ioredis');const redis = new Redis({  host: '127.0.0.1',  port: 6379,  password: 'YourRedisPass',  db: 0,});module.exports = redis;// 使用：缓存用户信息const redis = require('../config/redis');async function getUser(id) {  const cacheKey = `user:${id}`;    // 先查缓存  const cached = await redis.get(cacheKey);  if (cached) {    return JSON.parse(cached);  }    // 查数据库  const user = await User.findById(id);  if (user) {    // 写入缓存，过期 10 分钟    await redis.setex(cacheKey, 600, JSON.stringify(user));  }  return user;}

const { Sequelize, DataTypes } = require('sequelize');const sequelize = new Sequelize('travel_db', 'root', '123456', {  host: 'localhost',  dialect: 'mysql',  logging: false,});// 定义模型const User = sequelize.define('User', {  username: { type: DataTypes.STRING(50), allowNull: false, unique: true },  email: { type: DataTypes.STRING(100), allowNull: false },  password: { type: DataTypes.STRING(255), allowNull: false },  status: { type: DataTypes.ENUM('active', 'inactive', 'banned'), defaultValue: 'active' },}, {  tableName: 'users',  timestamps: true,  underscored: true,});// 使用async function findAll() {  return await User.findAll({    attributes: ['id', 'username', 'email', 'status'],    order: [['created_at', 'DESC']],  });}

// utils/errors.jsclass BusinessException extends Error {  constructor(code, message) {    super(message);    this.status = 200;       // HTTP 状态码 200    this.code = code;        // 业务错误码  }}class ValidationError extends Error {  constructor(message) {    super(message);    this.status = 400;  }}class NotFoundError extends Error {  constructor(resource) {    super(`${resource} 不存在`);    this.status = 404;  }}class UnauthorizedError extends Error {  constructor(message = '未授权') {    super(message);    this.status = 401;  }}module.exports = { BusinessException, ValidationError, NotFoundError, UnauthorizedError };// 使用const { NotFoundError, ValidationError } = require('../utils/errors');router.get('/users/:id', async (ctx) => {  const user = await userService.findById(ctx.params.id);  if (!user) {    throw new NotFoundError('用户');  // 会被全局错误中间件捕获  }  ctx.body = user;});

// middlewares/response.jsfunction success(ctx, data, message = 'success') {  ctx.body = {    code: 0,    message,    data,  };}function error(ctx, code, message) {  ctx.body = {    code,    message,    data: null,  };}function paginate(ctx, list, total, page, size) {  ctx.body = {    code: 0,    message: 'success',    data: {      list,      total,      page: Number(page),      size: Number(size),      totalPages: Math.ceil(total / size),    },  };}module.exports = { success, error, paginate };// 使用const { success, paginate } = require('../middlewares/response');router.get('/users', async (ctx) => {  const { page = 1, size = 10 } = ctx.query;  const result = await userService.findAll(page, size);  paginate(ctx, result.list, result.total, page, size);});router.post('/users', async (ctx) => {  const user = await userService.create(ctx.request.body);  success(ctx, user, '创建成功');});

const jwt = require('jsonwebtoken');const bcrypt = require('bcryptjs');const SECRET = 'your-secret-key';router.post('/auth/register', async (ctx) => {  const { username, password, email } = ctx.request.body;    // 检查用户名是否已存在  const existing = await userService.findByUsername(username);  if (existing) {    ctx.status = 409;    ctx.body = { code: 409, message: '用户名已存在' };    return;  }    // 加密密码  const hashedPassword = await bcrypt.hash(password, 10);    // 创建用户  const user = await userService.create({    username,    email,    password: hashedPassword,  });    // 生成 token  const token = jwt.sign(    { sub: user.id, username: user.username },    SECRET,    { expiresIn: '7d' }  );    ctx.body = {    code: 0,    message: '注册成功',    data: { user: { id: user.id, username: user.username }, token },  };});router.post('/auth/login', async (ctx) => {  const { username, password } = ctx.request.body;    const user = await userService.findByUsername(username);  if (!user) {    ctx.status = 401;    ctx.body = { code: 401, message: '用户名或密码错误' };    return;  }    const valid = await bcrypt.compare(password, user.password);  if (!valid) {    ctx.status = 401;    ctx.body = { code: 401, message: '用户名或密码错误' };    return;  }    const token = jwt.sign(    { sub: user.id, username: user.username },    SECRET,    { expiresIn: '7d' }  );    ctx.body = {    code: 0,    message: '登录成功',    data: { user: { id: user.id, username: user.username }, token },  };});

// middlewares/auth.jsconst jwt = require('jsonwebtoken');const SECRET = 'your-secret-key';// 不需要认证的路由const publicPaths = [  /^\/api\/auth\/register/,  /^\/api\/auth\/login/,];function isPublic(path) {  return publicPaths.some(pattern => pattern.test(path));}module.exports = async function auth(ctx, next) {  // 公开路由跳过  if (isPublic(ctx.path)) {    return await next();  }    const authHeader = ctx.header.authorization;  if (!authHeader || !authHeader.startsWith('Bearer ')) {    ctx.status = 401;    ctx.body = { code: 401, message: '请提供认证 token' };    return;  }    const token = authHeader.replace('Bearer ', '');    try {    const decoded = jwt.verify(token, SECRET);    ctx.state.user = decoded;  // 把用户信息挂到 ctx.state    await next();  } catch (err) {    ctx.status = 401;    ctx.body = { code: 401, message: 'token 无效或已过期' };  }};// 使用app.use(auth);  // 在路由之前app.use(router.routes());

// middlewares/role.jsmodule.exports = (...roles) => {  return async (ctx, next) => {    if (!ctx.state.user) {      ctx.status = 401;      ctx.body = { code: 401, message: '未登录' };      return;    }        if (!roles.includes(ctx.state.user.role)) {      ctx.status = 403;      ctx.body = { code: 403, message: '权限不足' };      return;    }        await next();  };};// 使用const requireRole = require('../middlewares/role');router.get('/admin/users', requireRole('admin'), async (ctx) => {  // 只有 admin 能访问  ctx.body = await userService.findAll();});

src/├── app.js                    # 入口├── config/│   ├── index.js              # 环境配置│   ├── database.js           # 数据库配置│   └── redis.js              # Redis 配置├── middlewares/│   ├── error.js              # 全局错误处理│   ├── auth.js               # JWT 认证│   ├── role.js               # 角色权限│   └── response.js           # 统一响应├── routes/│   ├── index.js              # 路由汇总│   ├── auth.routes.js│   ├── user.routes.js│   └── order.routes.js├── controllers/│   ├── auth.controller.js│   ├── user.controller.js│   └── order.controller.js├── services/│   ├── auth.service.js│   ├── user.service.js│   └── order.service.js├── models/│   └── user.model.js├── utils/│   ├── errors.js             # 自定义错误│   └── validator.js          # 参数验证└── validators/    └── user.validator.js     # DTO 验证

// app.jsconst Koa = require('koa');const bodyParser = require('koa-bodyparser');const cors = require('koa2-cors');const logger = require('koa-logger');const helmet = require('koa-helmet');const errorHandler = require('./middlewares/error');const authMiddleware = require('./middlewares/auth');const routes = require('./routes');const app = new Koa();// 1. 安全头app.use(helmet());// 2. 请求日志app.use(logger());// 3. CORSapp.use(cors({ origin: '*' }));// 4. 请求体解析app.use(bodyParser());// 5. 全局错误处理（必须放最前面）app.use(errorHandler);// 6. JWT 认证app.use(authMiddleware);// 7. 路由app.use(routes.routes()).use(routes.allowedMethods());// 8. 404app.use(async (ctx) => {  ctx.status = 404;  ctx.body = { code: 404, message: 'Not Found' };});const PORT = process.env.PORT || 3000;app.listen(PORT, () => {  console.log(`Server running on http://localhost:${PORT}`);});

// controllers/user.controller.jsconst userService = require('../services/user.service');const { success, paginate } = require('../middlewares/response');const { NotFoundError, ValidationError } = require('../utils/errors');module.exports = {  async findAll(ctx) {    const { page = 1, size = 10, keyword } = ctx.query;    const result = await userService.findAll({ page, size, keyword });    paginate(ctx, result.list, result.total, page, size);  },  async findById(ctx) {    const user = await userService.findById(ctx.params.id);    if (!user) throw new NotFoundError('用户');    success(ctx, user);  },  async create(ctx) {    const { username, email, password } = ctx.request.body;        // 参数验证    if (!username || !email || !password) {      throw new ValidationError('用户名、邮箱、密码不能为空');    }    if (password.length < 6) {      throw new ValidationError('密码至少 6 位');    }        const user = await userService.create(ctx.request.body);    success(ctx, user, '创建成功');  },  async update(ctx) {    const user = await userService.update(ctx.params.id, ctx.request.body);    success(ctx, user, '更新成功');  },  async delete(ctx) {    await userService.delete(ctx.params.id);    success(ctx, null, '删除成功');  },};

// services/user.service.jsconst pool = require('../config/database');const bcrypt = require('bcryptjs');const { ConflictError, NotFoundError } = require('../utils/errors');class UserService {  async findAll({ page = 1, size = 10, keyword }) {    const offset = (page - 1) * size;    let sql = 'SELECT id, username, email, status, created_at FROM users';    let countSql = 'SELECT COUNT(*) as total FROM users';    const params = [];        if (keyword) {      sql += ' WHERE username LIKE ?';      countSql += ' WHERE username LIKE ?';      params.push(`%${keyword}%`);    }        sql += ' ORDER BY id DESC LIMIT ? OFFSET ?';        const [rows] = await pool.query(sql, [Number(size), Number(offset)]);    const [[{ total }]] = await pool.query(countSql, params);        return { list: rows, total };  }  async findById(id) {    const [rows] = await pool.query(      'SELECT id, username, email, status, created_at FROM users WHERE id = ?',      [id]    );    return rows[0];  }  async findByUsername(username) {    const [rows] = await pool.query('SELECT * FROM users WHERE username = ?', [username]);    return rows[0];  }  async create(data) {    const existing = await this.findByUsername(data.username);    if (existing) throw new ConflictError('用户名已存在');        const hashedPassword = await bcrypt.hash(data.password, 10);    const [result] = await pool.query(      'INSERT INTO users (username, email, password) VALUES (?, ?, ?)',      [data.username, data.email, hashedPassword]    );    return { id: result.insertId, username: data.username, email: data.email };  }  async update(id, data) {    const user = await this.findById(id);    if (!user) throw new NotFoundError('用户');        const fields = [];    const values = [];    if (data.email) { fields.push('email = ?'); values.push(data.email); }    if (data.status) { fields.push('status = ?'); values.push(data.status); }    if (data.password) {      const hashed = await bcrypt.hash(data.password, 10);      fields.push('password = ?'); values.push(hashed);    }        if (fields.length > 0) {      values.push(id);      await pool.query(`UPDATE users SET ${fields.join(', ')} WHERE id = ?`, values);    }    return this.findById(id);  }  async delete(id) {    const user = await this.findById(id);    if (!user) throw new NotFoundError('用户');    await pool.query('DELETE FROM users WHERE id = ?', [id]);  }}module.exports = new UserService();

// routes/upload.routes.jsconst Router = require('@koa/router');const multer = require('@koa/multer');const path = require('path');const fs = require('fs');const router = new Router({ prefix: '/api/upload' });// 确保上传目录存在const uploadDir = path.join(__dirname, '../../uploads');if (!fs.existsSync(uploadDir)) {  fs.mkdirSync(uploadDir, { recursive: true });}const storage = multer.diskStorage({  destination: (req, file, cb) => cb(null, uploadDir),  filename: (req, file, cb) => {    const ext = path.extname(file.originalname);    cb(null, `${Date.now()}-${Math.round(Math.random() * 1e9)}${ext}`);  },});const upload = multer({  storage,  limits: { fileSize: 5 * 1024 * 1024 },  fileFilter: (req, file, cb) => {    const allowed = /jpeg|jpg|png|gif|webp/;    if (allowed.test(path.extname(file.originalname).toLowerCase())) {      cb(null, true);    } else {      cb(new Error('只支持图片格式'));    }  },});router.post('/single', upload.single('file'), (ctx) => {  ctx.body = {    code: 0,    data: {      url: `/uploads/${ctx.file.filename}`,      filename: ctx.file.filename,      size: ctx.file.size,    },  };});router.post('/multiple', upload.array('files', 10), (ctx) => {  ctx.body = {    code: 0,    data: ctx.files.map(f => ({      url: `/uploads/${f.filename}`,      filename: f.filename,    })),  };});module.exports = router;// app.js 中添加静态文件服务const serve = require('koa-static');app.use(serve(path.join(__dirname, 'uploads')));

# docker-compose.ymlversion: '3.8'services:  api:    build: .    ports:      - "3000:3000"    environment:      - NODE_ENV=production      - DB_HOST=mysql      - REDIS_HOST=redis    depends_on:      - mysql      - redis    restart: always  mysql:    image: mysql:8    environment:      MYSQL_ROOT_PASSWORD: rootpassword      MYSQL_DATABASE: travel_db    volumes:      - mysql-data:/var/lib/mysql  redis:    image: redis:7-alpine    volumes:      - redis-data:/datavolumes:  mysql-data:  redis-data: