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Next.js 15 Fullstack (App Router + Server Actions) · 课时

守卫与角色

使用 NestJS 守卫保护路由，并实现基于角色的访问控制（RBAC）来管理用户权限。

守卫与角色 是 CoddyKit 上的免费 Next.js 15 Fullstack (App Router + Server Actions) 课时。 这是第 4 节课，共 6 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Next.js 15 Fullstack (App Router + Server Actions) 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Next.js 15 Fullstack (App Router + Server Actions) 课程共包含 6 节课。

本课时的部分内容尚未翻译，以英文显示。

What are NestJS Guards?

In NestJS, Guards are special classes that decide if a given request should be processed by the route handler. Think of them as gatekeepers!

They sit between the incoming request and your application's logic, making authorization decisions.

  • Authorization: Who is allowed to do what?
  • Authentication: Who is this user? (Often handled before guards, but guards can confirm it).

Building a Basic Guard

All NestJS Guards must implement the CanActivate interface. This interface requires a single method: canActivate().

The canActivate() method returns a boolean, a Promise<boolean>, or an Observable<boolean>. If it returns true, the request proceeds; if false, it's blocked.

import { CanActivate, ExecutionContext, Injectable } from '@nestjs/common';
import { Observable } from 'rxjs';

@Injectable()
export class AuthGuard implements CanActivate {
  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    // Logic to determine if user is authorized
    // For now, let's just allow it
    return true;
  }
}

A Simple Authentication Check

Let's make our AuthGuard actually do something! We'll simulate checking if a user is 'logged in' by looking for a specific header.

The ExecutionContext provides access to the request, response, and more, allowing us to inspect the incoming request.

import { CanActivate, ExecutionContext, Injectable } from '@nestjs/common';
import { Observable } from 'rxjs';

@Injectable()
export class BasicAuthGuard implements CanActivate {
  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    const request = context.switchToHttp().getRequest();
    // In a real app, you'd check JWT, session, etc.
    // For this example, we check a simple header.
    const hasAuthHeader = request.headers['authorization'] === 'Bearer secret-token';
    return hasAuthHeader; // Only allow if header is correct
  }
}

Protecting Your Endpoints

To apply a guard, you use the @UseGuards() decorator. You can apply it to a single route handler or to an entire controller.

When applied to a controller, all routes within that controller will be protected by the guard.

import { Controller, Get, UseGuards } from '@nestjs/common';
import { BasicAuthGuard } from './common/guards/auth.guard';

@Controller('protected')
@UseGuards(BasicAuthGuard) // Protects all routes in this controller
export class ProtectedController {
  @Get()
  getProtectedData(): string {
    return 'This data is protected!';
  }

  @Get('public')
  getAnotherProtectedData(): string {
    return 'More protected data.';
  }
}

// src/app.module.ts
import { Module } from '@nestjs/common';
import { ProtectedController } from './app.controller';

@Module({
  controllers: [ProtectedController],
  providers: [],
})
export class AppModule {}

// src/main.ts
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
  console.log('App running on http://localhost:3000');
}
bootstrap();

Understanding RBAC

While basic authentication checks if a user is who they say they are, Role-Based Access Control (RBAC) checks what they are allowed to do.

With RBAC, users are assigned roles (e.g., 'admin', 'editor', 'viewer'), and permissions are granted to roles, not individual users.

  • Role: A collection of permissions (e.g., 'admin' can 'create', 'read', 'update', 'delete').
  • User: Assigned one or more roles.
  • Resource: The data or functionality being accessed.

Marking Routes with Roles

To implement RBAC, we need a way to tell our guard which roles are allowed for a specific route. NestJS allows us to create custom decorators for this!

We'll create an @Roles() decorator to attach role metadata to our route handlers.

import { SetMetadata } from '@nestjs/common';

export const ROLES_KEY = 'roles';
export const Roles = (...roles: string[]) => SetMetadata(ROLES_KEY, roles);

// Example usage in a controller:
// @Roles('admin', 'editor')
// @Get('admin-only')
// someAdminMethod() { ... }

The Roles Guard Logic

Now, let's build our RolesGuard. This guard will:

  1. Get the required roles from the route's metadata using the Reflector.
  2. Get the user's roles (e.g., from the request object after authentication).
  3. Compare them to see if the user has any of the required roles.
import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
import { Reflector } from '@nestjs/core';
import { Observable } from 'rxjs';
import { ROLES_KEY } from '../decorators/roles.decorator';

@Injectable()
export class RolesGuard implements CanActivate {
  constructor(private reflector: Reflector) {}

  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    const requiredRoles = this.reflector.getAllAndOverride<string[]>(ROLES_KEY, [
      context.getHandler(),
      context.getClass(),
    ]);

    if (!requiredRoles) {
      return true; // No roles defined, so access is allowed by default
    }

    const request = context.switchToHttp().getRequest();
    // In a real app, 'user' would come from an authentication guard
    // and contain actual user data including roles.
    const user = request.user || { roles: ['viewer'] }; // Dummy user for example

    const hasPermission = requiredRoles.some((role) => user.roles.includes(role));
    return hasPermission;
  }
}

Stacking Guards for Protection

You can use multiple guards on a single route or controller. NestJS executes guards in the order they are listed in the @UseGuards() decorator.

If any guard returns false, the request is immediately blocked, and subsequent guards (and the route handler) are not executed.

  • First: Authentication (Is the user logged in?)
  • Second: Authorization (Does the user have the right role?)

Applying Guards and Roles

Let's see how our BasicAuthGuard, RolesGuard, and @Roles() decorator work together to protect an endpoint.

We'll simulate a user with the 'admin' role.

import { Controller, Get, UseGuards, Req } from '@nestjs/common';
import { BasicAuthGuard } from './common/guards/auth.guard';
import { RolesGuard } from './common/guards/roles.guard';
import { Roles } from './common/decorators/roles.decorator';

// Assume this comes from a real authentication process
interface User {
  username: string;
  roles: string[];
}

@Controller('admin')
@UseGuards(BasicAuthGuard, RolesGuard) // Guards applied in order
export class AdminController {
  @Get('dashboard')
  @Roles('admin') // Only users with 'admin' role can access
  getAdminDashboard(@Req() req): string {
    // For this runnable example's context, manually set user.
    // In a real app, BasicAuthGuard would populate req.user.
    req.user = { username: 'testuser', roles: ['admin'] };
    return `Welcome to the Admin Dashboard, ${req.user.username}!`;
  }

  @Get('reports')
  @Roles('admin', 'editor') // Admins or Editors can access
  getReports(@Req() req): string {
    req.user = { username: 'editoruser', roles: ['editor'] };
    return `Accessing reports as ${req.user.username}.`;
  }
}

// src/app.module.ts
import { Module } from '@nestjs/common';
import { AdminController } from './app.controller';

@Module({
  controllers: [AdminController],
  providers: [],
})
export class AppModule {}

// src/main.ts (unchanged from previous runnable example)
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
  console.log('Admin app running on http://localhost:3000');
}
bootstrap();

Guard & Role Check

Consider a NestJS route protected by @UseGuards(AuthGuard, RolesGuard) and @Roles('admin', 'moderator').

If a request comes in with a valid authentication token (passed by AuthGuard), but the authenticated user has only the role 'viewer', what will happen?

Guards & Roles Summary

Great job! In this lesson, you learned about:

  • NestJS Guards: Gatekeepers that implement CanActivate to control route access.
  • @UseGuards(): Decorator to apply guards at controller or method level.
  • Role-Based Access Control (RBAC): Managing permissions based on user roles.
  • Custom Decorators: Using @SetMetadata() to attach custom data (like roles) to routes.
  • Reflector: Used by guards to read metadata from routes.

Guards are powerful for authorization. Next, you might explore how to integrate Passport.js strategies for more robust authentication!

常见问题解答

「守卫与角色」课时是免费的吗？

是的 — 「守卫与角色」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Next.js 15 Fullstack (App Router + Server Actions) 课程的其余内容，请升级到 CoddyKit PRO。 Next.js 15 Fullstack (App Router + Server Actions) 课程共包含 6 节课。

「守卫与角色」这节课中我会学到什么？

使用 NestJS 守卫保护路由，并实现基于角色的访问控制（RBAC）来管理用户权限。 你通过在浏览器中直接运行的动手代码来练习 Next.js 15 Fullstack (App Router + Server Actions)，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Next.js 15 Fullstack (App Router + Server Actions) 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Next.js 15 Fullstack (App Router + Server Actions) 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 6 节。

「守卫与角色」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Next.js 15 Fullstack (App Router + Server Actions) 课中编写并运行代码吗？

能。每节 Next.js 15 Fullstack (App Router + Server Actions) 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

  1. 集成 NextAuth.js
  2. JWT 策略实现
  3. 保护路由与数据
  4. 守卫与角色
  5. 自定义身份验证策略
  6. Passport.js 集成
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