请求响应

本章节介绍 Express.js 中的请求对象和响应对象的使用方法。

请求对象 (req)

常用属性

app.get('/info', (req, res) => {
  const info = {
    baseUrl: req.baseUrl,
    body: req.body,
    cookies: req.cookies,
    hostname: req.hostname,
    ip: req.ip,
    method: req.method,
    originalUrl: req.originalUrl,
    params: req.params,
    path: req.path,
    protocol: req.protocol,
    query: req.query,
    route: req.route,
    secure: req.secure,
    xhr: req.xhr,
    headers: req.headers
  };
  res.json(info);
});

路径参数

app.get('/users/:userId/books/:bookId', (req, res) => {
  const { userId, bookId } = req.params;
  res.json({ userId, bookId });
});

查询参数

app.get('/search', (req, res) => {
  const { q, page = 1, limit = 10 } = req.query;
  res.json({ query: q, page, limit });
});

请求体

app.use(express.json());
app.use(express.urlencoded({ extended: true }));

app.post('/users', (req, res) => {
  const { name, email } = req.body;
  res.json({ name, email });
});

请求头

app.get('/headers', (req, res) => {
  const auth = req.get('Authorization');
  const contentType = req.get('Content-Type');
  res.json({ auth, contentType });
});

文件上传

npm install multer

const multer = require('multer');
const upload = multer({ dest: 'uploads/' });

app.post('/upload', upload.single('file'), (req, res) => {
  res.json({
    file: req.file,
    body: req.body
  });
});

app.post('/photos', upload.array('photos', 12), (req, res) => {
  res.json({ files: req.files });
});

响应对象 (res)

发送响应

app.get('/send', (req, res) => {
  res.send('Hello World');
});

app.get('/json', (req, res) => {
  res.json({ message: 'Hello' });
});

app.get('/status', (req, res) => {
  res.status(201).json({ created: true });
});

设置状态码

app.get('/not-found', (req, res) => {
  res.status(404).send('Not Found');
});

app.get('/error', (req, res) => {
  res.status(500).json({ error: 'Internal Server Error' });
});

设置响应头

app.get('/headers', (req, res) => {
  res.set('X-Custom-Header', 'value');
  res.set({
    'Content-Type': 'application/json',
    'Cache-Control': 'no-cache'
  });
  res.json({ headers: 'set' });
});

Cookie 操作

app.get('/set-cookie', (req, res) => {
  res.cookie('name', 'express', { 
    maxAge: 900000, 
    httpOnly: true 
  });
  res.send('Cookie 已设置');
});

app.get('/clear-cookie', (req, res) => {
  res.clearCookie('name');
  res.send('Cookie 已清除');
});

重定向

app.get('/redirect', (req, res) => {
  res.redirect('/home');
});

app.get('/redirect-external', (req, res) => {
  res.redirect('https://expressjs.com');
});

app.get('/redirect-status', (req, res) => {
  res.redirect(301, '/new-url');
});

文件下载

app.get('/download', (req, res) => {
  res.download('/files/report.pdf');
});

app.get('/download-custom', (req, res) => {
  res.download('/files/report.pdf', 'report.pdf', (err) => {
    if (err) {
      console.error(err);
    }
  });
});

发送文件

app.get('/file', (req, res) => {
  res.sendFile('/files/index.html', { root: __dirname });
});

渲染模板

app.set('view engine', 'ejs');

app.get('/profile', (req, res) => {
  res.render('profile', { 
    name: 'Express',
    version: '4.x'
  });
});

响应格式化

统一响应格式

const response = {
  success: (res, data, message = 'Success') => {
    res.json({
      code: 0,
      message,
      data
    });
  },
  
  error: (res, message = 'Error', code = 1, status = 400) => {
    res.status(status).json({
      code,
      message,
      data: null
    });
  }
};

app.get('/users', (req, res) => {
  const users = [{ id: 1, name: 'User' }];
  response.success(res, users);
});

app.get('/error', (req, res) => {
  response.error(res, '资源未找到', 404, 404);
});

分页响应

app.get('/posts', async (req, res) => {
  const { page = 1, limit = 10 } = req.query;
  const posts = await Post.find()
    .skip((page - 1) * limit)
    .limit(limit);
  const total = await Post.countDocuments();
  
  res.json({
    data: posts,
    pagination: {
      page: parseInt(page),
      limit: parseInt(limit),
      total,
      pages: Math.ceil(total / limit)
    }
  });
});