feat: 实现成绩管理系统核心功能

添加响应工具、错误处理中间件和数据库模型
创建用户、学生、课程和成绩相关服务
实现管理员、教师和学生控制器的基本功能
重构路由处理并优化数据库查询

backend/services/adminService.js

@@ -0,0 +1,60 @@
+const db = require('../config/database');
+const bcrypt = require('bcryptjs');
+const User = require('../models/User');
+
+class AdminService {
+    static async getUsers(params) {
+        const { page = 1, limit = 10, search = '', role = '' } = params;
+        const offset = (page - 1) * limit;
+        
+        let queryStr = 'SELECT id, name, role, class, created_at FROM users WHERE 1=1';
+        let queryParams = [];
+        
+        if (search) {
+            queryStr += ' AND (id LIKE ? OR name LIKE ? OR class LIKE ?)';
+            const searchTerm = `%${search}%`;
+            queryParams.push(searchTerm, searchTerm, searchTerm);
+        }
+        
+        if (role) {
+            queryStr += ' AND role = ?';
+            queryParams.push(role);
+        }
+        
+        // Count
+        const countSql = queryStr.replace('SELECT id, name, role, class, created_at', 'SELECT COUNT(*) as total');
+        const countRows = await db.query(countSql, queryParams);
+        const total = countRows[0].total;
+        
+        // Data
+        queryStr += ' ORDER BY created_at DESC LIMIT ? OFFSET ?';
+        queryParams.push(parseInt(limit), parseInt(offset));
+        
+        const users = await db.query(queryStr, queryParams);
+        
+        return {
+            data: users,
+            pagination: {
+                page: parseInt(page),
+                limit: parseInt(limit),
+                total,
+                pages: Math.ceil(total / limit)
+            }
+        };
+    }
+
+    static async createUser(userData) {
+        const { id } = userData;
+        
+        // 检查 ID
+        const existingUser = await User.findById(id);
+        if (existingUser) {
+            throw new Error('用户ID已存在');
+        }
+
+        // 创建用户
+        return await User.create(userData);
+    }
+}
+
+module.exports = AdminService;