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

JWT 策略实现

集成 JSON Web Token（JWT）实现无状态身份验证，涵盖令牌生成与验证。

JWT 策略实现 是 CoddyKit 上的免费 Next.js 15 Fullstack (App Router + Server Actions) 课时。这是第 2 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 is a JSON Web Token (JWT)?

Welcome! In this lesson, we'll dive into JSON Web Tokens (JWTs), a popular method for securing APIs.

JWTs are compact, URL-safe means of representing claims to be transferred between two parties.
They are often used for stateless authentication, meaning the server doesn't need to store session information.
This makes APIs more scalable and easier to manage, especially in distributed systems.

JWT's Three Main Parts

A JWT is essentially a long string, but it's structured into three distinct parts, separated by dots (.):

Header: Contains metadata about the token itself (e.g., type of token, signing algorithm).
Payload: Contains the actual claims or data about the user and additional properties.
Signature: Used to verify the token's integrity and authenticity.

Each part is Base64Url-encoded.

Header & Payload in Detail

Let's look closer at the first two parts:

Header: Typically contains two fields:"alg" (algorithm, e.g., HS256) and "typ" (type, which is JWT).
Payload: This is where you put your data, known as 'claims'. Common claims include:
- sub (subject): Usually the user ID.
- exp (expiration time): When the token expires.
- iat (issued at): When the token was issued.
- Custom claims: Any other data you need, like "username" or "role".

The Cryptographic Signature

The signature is the crucial third part that ensures security:

It's created by taking the encoded header, the encoded payload, a secret key, and the algorithm specified in the header.
This combination is then cryptographically hashed.
Why is it important? If anyone tries to tamper with the header or payload, the signature verification will fail, indicating the token is invalid or has been altered.
The secret key must be kept confidential on the server side!

NestJS and JWTs

NestJS provides excellent support for integrating JWTs, leveraging the power of the jsonwebtoken library under the hood.

We'll primarily use the @nestjs/jwt package, which offers a JwtModule and JwtService to handle token generation and verification seamlessly within your application.

First, you'll need to install the package if you haven't already:

npm install @nestjs/jwt passport-jwt --save

Configuring the JwtModule

To use JWTs in NestJS, you need to import and configure the JwtModule in your application's module (e.g., AppModule or a dedicated AuthModule).

The most important option is the secret key, which is used to sign and verify tokens.

import { Module } from '@nestjs/common';
import { JwtModule } from '@nestjs/jwt';

@Module({
  imports: [
    JwtModule.register({
      secret: 'yourSuperSecretKey',
      signOptions: { expiresIn: '60s' }, // e.g., 60s, 7d, 1h
    }),
  ],
  // ... other providers, controllers
})
export class AppModule {}

Generating a JWT in NestJS

Once JwtModule is configured, you can inject JwtService into your services to generate (sign) new tokens. The sign() method takes a payload (usually an object) and creates the JWT string.

import { Injectable } from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';

@Injectable()
export class AuthService {
  constructor(private jwtService: JwtService) {}

  async signIn(user: any): Promise<string> {
    const payload = { username: user.username, sub: user.userId };
    return this.jwtService.sign(payload); // Signs with configured secret & options
  }
}

Code Demo: Token Generation

Let's see how a token is generated conceptually. This example uses the underlying jsonwebtoken library directly, similar to how NestJS does it.

Run this code to see a JWT being created:

// To run this, install 'jsonwebtoken':
// npm install jsonwebtoken --save

const jwt = require('jsonwebtoken');

const payload = {
  sub: 'user123',
  username: 'coder_kit'
};

const secret = 'mySuperSecretKey123'; // Keep this secret safe!

// Sign the token with an expiration of 1 hour
const token = jwt.sign(payload, secret, { expiresIn: '1h' });

console.log('--- Generated JWT ---');
console.log(token);
console.log('\nThis token is valid for 1 hour.');

Verifying a JWT in NestJS

When a client sends a JWT, your server needs to verify it. The JwtService.verify() method checks several things:

Is the signature valid (i.e., was it signed with our secret)?
Has the token expired?
Are there any other validation rules specified?

If valid, it returns the decoded payload. If invalid, it throws an error.

import { Injectable } from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';

@Injectable()
export class AuthService {
  constructor(private jwtService: JwtService) {}

  async verifyToken(token: string): Promise<any> {
    try {
      const payload = this.jwtService.verify(token);
      return payload; // Token is valid, return its data
    } catch (error) {
      // Token is invalid or expired
      throw new Error('Invalid or expired token');
    }
  }
}

Code Demo: Token Verification

Here's how token verification works. You can use the token generated in the previous step (or the example provided) and see it being verified.

Remember, the secret used for verification MUST be the same one used for signing!

// To run this, install 'jsonwebtoken':
// npm install jsonwebtoken --save

const jwt = require('jsonwebtoken');

// IMPORTANT: Replace with a REAL token you generated,
// or use this example token (signed with 'mySuperSecretKey123')
const testToken = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c2VyMTIzIiwidXNlcm5hbWUiOiJjb2Rlcl9raXQiLCJpYXQiOjE3MDcwOTMyMTMsImV4cCI6MTcwNzE3OTYxM30.4i-J_q_e_x_a_m_p_l_e_s_i_g_n_a_t_u_r_e_f_o_r_d_e_m_o'; 

const secret = 'mySuperSecretKey123'; // Must match the signing secret!

console.log('--- Attempting to Verify Token ---');
try {
  const decoded = jwt.verify(testToken, secret);
  console.log('Token is VALID!');
  console.log('Decoded Payload:');
  console.log(decoded);
} catch (error) {
  console.error('Token is INVALID or EXPIRED!');
  console.error('Error:', error.message);
}

JWT Concept Check

You've learned about the three main parts of a JWT. Which of the following components is primarily responsible for ensuring the token's integrity (that it hasn't been tampered with)?

Recap: JWT Essentials

Great job! You've covered the fundamentals of JWTs:

What they are: Compact, stateless tokens for authentication.
Their structure: Header, Payload, and Signature.
Key concepts: How the signature protects integrity and the role of the secret key.
NestJS integration: Using @nestjs/jwt to configure, sign, and verify tokens.

Next, we'll explore how to protect routes using Guards and implement role-based access control!

常见问题解答

「JWT 策略实现」课时是免费的吗？

是的 — 「JWT 策略实现」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。

「JWT 策略实现」这节课中我会学到什么？

集成 JSON Web Token（JWT）实现无状态身份验证，涵盖令牌生成与验证。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 2 节课，共 6 节。

「JWT 策略实现」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

← 返回 Next.js 15 Fullstack (App Router + Server Actions)