diff --git a/后端 b/后端
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+const express = require('express');
+const cors = require('cors');
+const bodyParser = require('body-parser');
+const bcrypt = require('bcrypt');
+const { body, validationResult } = require('express-validator');
+const morgan = require('morgan');
+const timeout = require('connect-timeout');
+const multer = require('multer');
+const path = require('path');
+const fs = require('fs');
+const rateLimit = require('express-rate-limit');
+
+// 创建 Express 应用实例
+const app = express();
+const PORT = 3000; // 可以根据需要修改端口
+const uploadDir = 'uploads/';
+
+// 使用中间件
+app.use(cors({
+    origin: 'http://your-frontend-domain.com', // 修改为你前端的域名
+    methods: ['GET', 'POST'],
+    allowedHeaders: ['Content-Type']
+}));
+app.use(express.json()); // 解析 JSON 格式的请求体
+app.use(morgan('combined')); // 记录 HTTP 请求日志
+
+// 请求限制
+const limiter = rateLimit({
+    windowMs: 15 * 60 * 1000, // 15 分钟
+    max: 100 // 每个 IP 限制 100 次请求
+});
+app.use(limiter); // 应用限制
+
+// 检查并创建上传目录
+if (!fs.existsSync(uploadDir)) {
+    fs.mkdirSync(uploadDir, { recursive: true });
+}
+
+// 设置文件存储配置
+const storage = multer.diskStorage({
+    destination: (req, file, cb) => {
+        cb(null, uploadDir);
+    },
+    filename: (req, file, cb) => {
+        cb(null, Date.now() + path.extname(file.originalname));
+    }
+});
+
+// 创建上传实例
+const upload = multer({ 
+    storage,
+    limits: { fileSize: 5 * 1024 * 1024 }, // 限制文件大小为 5MB
+    fileFilter: (req, file, cb) => {
+        const filetypes = /jpeg|jpg|png|gif|pdf/;
+        const mimetype = filetypes.test(file.mimetype);
+        const extname = filetypes.test(path.extname(file.originalname).toLowerCase());
+
+        if (mimetype && extname) {
+            return cb(null, true);
+        }
+        cb(new Error('只允许上传 JPEG、PNG、GIF 和 PDF 文件'));
+    }
+});
+
+// 模拟的用户数据（在实际应用中，这通常来自数据库）
+let users = []; // 应该替换为实际的数据库
+
+// 注册接口
+app.post('/api/register', [
+    body('username').notEmpty().withMessage('用户名不能为空'),
+    body('password').notEmpty().withMessage('密码不能为空'),
+    body('confirm_password').custom((value, { req }) => {
+        if (value !== req.body.password) {
+            throw new Error('密码不匹配');
+        }
+        return true;
+    })
+], async (req, res) => {
+    const errors = validationResult(req);
+    if (!errors.isEmpty()) {
+        return res.status(400).json({ errors: errors.array() });
+    }
+
+    const { username, password } = req.body;
+    const existingUser = users.find(user => user.username === username);
+    if (existingUser) {
+        return res.status(400).send('用户名已被注册');
+    }
+
+    const hashedPassword = await bcrypt.hash(password, 10);
+    users.push({ username, password: hashedPassword });
+    res.status(201).send('注册成功');
+});
+
+// 登录接口
+app.post('/api/login', [
+    body('username').isString().notEmpty(),
+    body('password').isString().notEmpty()
+], (req, res) => {
+    const errors = validationResult(req);
+    if (!errors.isEmpty()) {
+        return res.status(400).json({ errors: errors.array() });
+    }
+
+    const { username, password } = req.body;
+    const user = users.find(u => u.username === username);
+
+    if (user && bcrypt.compareSync(password, user.password)) {
+        return res.status(200).json({ message: 'Login successful!' });
+    } else {
+        return res.status(401).json({ message: 'Invalid username or password.' });
+    }
+});
+
+// 获取数据接口
+app.get('/api/data', (req, res) => {
+    return res.status(200).json({ title: "欢迎使用系统", description: "这是一个模拟的系统，用于展示数据与交互" });
+});
+app.use(cors({
+    origin: 'http://your-frontend-domain.com', // 指定允许的源
+    methods: ['GET', 'POST'],
+}));
+app.use(express.json());
+app.use(express.static(path.join(__dirname, 'public'))); // 提供静态文件
+app.use(morgan('combined')); // 记录请求日志
+
+// 创建上传目录
+const uploadsDir = path.join(__dirname, 'uploads');
+if (!fs.existsSync(uploadsDir)) {
+    fs.mkdirSync(uploadsDir, { recursive: true });
+}
+
+// Multer setup for file uploads
+const storage = multer.diskStorage({
+    destination: (req, file, cb) => {
+        cb(null, uploadsDir); // 确保上传目录存在
+    },
+    filename: (req, file, cb) => {
+        cb(null, Date.now() + path.extname(file.originalname)); // Append timestamp to avoid name collisions
+    }
+});
+
+const upload = multer({
+    storage,
+    limits: {
+        fileSize: 5 * 1024 * 1024 // 限制文件大小为5MB
+    },
+    fileFilter: (req, file, cb) => {
+        const filetypes = /csv|txt|json/; // 允许的文件类型
+        const extname = filetypes.test(path.extname(file.originalname).toLowerCase());
+        const mimetype = filetypes.test(file.mimetype);
+        
+        if (mimetype && extname) {
+            return cb(null, true);
+        }
+        cb(new Error('Error: File type not supported!'));
+    }
+});
+
+// Endpoint to handle file import
+app.post('/import', upload.single('file'), (req, res) => {
+    if (!req.file) {
+        return res.status(400).send('No file uploaded.');
+    }
+    console.log(req.file);
+    res.send('File imported successfully!');
+});
+
+// Endpoint to handle file export
+app.get('/export', (req, res) => {
+    const filePath = path.join(__dirname, 'exports', 'sample-data.csv'); // 确保该文件存在
+    res.download(filePath, 'sample-data.csv', (err) => {
+        if (err) {
+            console.error(err);
+            res.status(500).send('Error exporting file.');
+        }
+    });
+});
+
+
+// 提交成绩接口
+app.post('/api/submit-grade', [
+    body('grade').isNumeric()
+], (req, res) => {
+    const errors = validationResult(req);
+    if (!errors.isEmpty()) {
+        return res.status(400).json({ errors: errors.array() });
+    }
+
+    const { grade } = req.body;
+    console.log(`Received grade: ${grade}`);
+    return res.status(200).json({ message: 'Grade submitted successfully!', grade });
+});
+
+// 文件上传接口
+app.post('/api/upload-file', upload.single('file'), (req, res) => {
+    if (!req.file) {
+        return res.status(400).json({ message: '没有文件上传' });
+    }
+    res.status(200).json({ message: '文件上传成功', filename: req.file.filename });
+});
+
+// 新增 Snum-data 接口
+app.post('/api/Snum-data', (req, res) => {
+    const { Number } = req.body;
+    // 检查请求体中的数据
+    if (typeof Number === 'undefined') {
+        return res.status(400).json({ message: 'Number is required' });
+    }
+    console.log('Received data:', Number);
+
+    res.status(200).json({ message: 'Data received successfully', data: { Number } });
+});
+
+// 全局错误处理
+app.use((err, req, res, next) => {
+    console.error(err.stack);
+    res.status(500).send('服务器内部错误');
+});
+// 路由
+app.get('/api/hello', (req, res) => {
+    res.send('Hello, world!');
+});
+
+
+// 启动服务器
+app.listen(PORT, () => {
+    console.log(`Server is running on http://localhost:${PORT}`);
+});
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