如何在NextJS页面路由中获取登录用户的ID？

要直接在auth()返回的用户对象中获取id字段，你需要通过NextAuth的session回调自定义返回的session内容，同时扩展TypeScript类型以支持自定义字段：

1. 修改auth.ts添加Session回调 #

在你的auth.ts配置中，添加callbacks.session函数，将数据库用户的id注入到session对象里：

import NextAuth from 'next-auth';
import Credentials from 'next-auth/providers/credentials';
import { authConfig } from './auth.config';
import { z } from 'zod';
import { sql } from '@vercel/postgres';
import type { User } from '@/app/lib/definitions';
import bcrypt from 'bcrypt';

async function getUser(email: string): Promise<User | undefined> {
  try {
    const user = await sql<User>`SELECT * FROM users WHERE email=${email}`;
    return user.rows[0];
  } catch (error) {
    console.error('Failed to fetch user:', error);
    throw new Error('Failed to fetch user.');
  }
}
 
export const { auth, signIn, signOut } = NextAuth({
  ...authConfig,
  callbacks: {
    // 保留原有的authorized回调
    authorized({ auth, request: { nextUrl } }) {
      const isLoggedIn = !!auth?.user;
      const isOnDashboard = nextUrl.pathname.startsWith('/dashboard');
      if (isOnDashboard) {
        if (isLoggedIn) return true;
        return false;
      } else if (isLoggedIn) {
        return Response.redirect(new URL('/dashboard', nextUrl));
      }
      return true;
    },
    // 添加session回调，注入用户id
    async session({ session, user }) {
      if (session.user && user.id) {
        session.user.id = user.id;
      }
      return session;
    },
  },
  providers: [
    Credentials({
      async authorize(credentials) {
        const parsedCredentials = z
          .object({ email: z.string().email(), password: z.string().min(6) })
          .safeParse(credentials);
 
        if (parsedCredentials.success) {
          const { email, password } = parsedCredentials.data;
          const user = await getUser(email);
          if (!user) return null;

          const passwordsMatch = await bcrypt.compare(password, user.password);
          if (passwordsMatch){
            return user;
          }
        }
 
        console.log('Invalid credentials');
        return null;
      },
    }),
  ],
});

2. 扩展NextAuth TypeScript类型 #

由于NextAuth默认的User和Session类型不包含id字段，需要创建类型扩展文件（比如types/next-auth.d.ts）让TypeScript识别自定义字段：

import NextAuth from "next-auth";
import type { User as AppUser } from "@/app/lib/definitions";

declare module "next-auth" {
  // 复用你定义的User类型
  interface User extends AppUser {}

  interface Session {
    user: User;
  }
}

3. 验证效果 #

修改完成后，重新启动项目，在dashboard/page.tsx中调用auth()就能直接获取包含id的用户对象：

const user = await auth();
console.log(user);
// 输出示例：
// {
//   user: { id: "1", name: 'User toto', email: 'user@nextmail.com' },
//   expires: '2025-01-12T13:47:17.724Z'
// }

原理说明 #

NextAuth默认只会将name、email、image字段存入session，通过session回调可以将authorize函数返回的完整用户对象中的id（或其他自定义字段）注入到session中，这样后续通过auth()获取session时就能直接拿到这些字段，无需额外查询数据库。

内容的提问来源于stack exchange，提问作者Haifisch