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Adds a "Calling `x()` after streaming has started" example to the `notFound`, `forbidden`, and `unauthorized` references. - The check lives in the data-access function that loads the data, inside a `<Suspense>` boundary, so the page shell keeps streaming (blog post 404, account 401, admin projects 403). - Documents the status-code trade-off: the interrupt fires after headers are sent, so the response is a `200`; a `loading.tsx` is part of the stream, not a way around it; `instant = false` opts the route out of the shell for a real status code. - Links the authentication guide's DAL section instead of re-teaching it, plus a good-to-know on floating promises never rendering the UI. Docs-only.
284 lines
8.9 KiB
Plaintext
284 lines
8.9 KiB
Plaintext
---
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title: forbidden
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description: API Reference for the forbidden function.
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version: experimental
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related:
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links:
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- app/api-reference/file-conventions/forbidden
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- app/api-reference/functions/not-found
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- app/api-reference/functions/unauthorized
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- app/api-reference/config/next-config-js/authInterrupts
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---
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The `forbidden` function throws an error that renders a Next.js 403 page. It's useful for handling authorization errors in your application. You can customize the UI using the [`forbidden.js` file](/docs/app/api-reference/file-conventions/forbidden).
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Invoking `forbidden()` throws a `NEXT_HTTP_ERROR_FALLBACK;403` error and terminates rendering of the route segment where it was thrown. Next.js also injects a `<meta name="robots" content="noindex" />` tag so the page is not indexed. Because it works by throwing, call it in the render path: a component, or a function a component `await`s. A call left in an un-awaited promise throws where nothing catches it, and no forbidden UI renders.
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To start using `forbidden`, enable the experimental [`authInterrupts`](/docs/app/api-reference/config/next-config-js/authInterrupts) configuration option in your `next.config.js` file:
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```ts filename="next.config.ts" switcher
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import type { NextConfig } from 'next'
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const nextConfig: NextConfig = {
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experimental: {
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authInterrupts: true,
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},
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}
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export default nextConfig
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```
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```js filename="next.config.js" switcher
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module.exports = {
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experimental: {
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authInterrupts: true,
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},
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}
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```
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`forbidden` can be invoked in [Server Components](/docs/app/getting-started/server-and-client-components), [Server Functions](/docs/app/getting-started/mutating-data), and [Route Handlers](/docs/app/api-reference/file-conventions/route).
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```tsx filename="app/admin/page.tsx" switcher
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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export default async function AdminPage() {
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const session = await verifySession()
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// Check if the user has the 'admin' role
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if (session.role !== 'admin') {
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forbidden()
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}
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// Render the admin page for authorized users
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return <></>
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}
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```
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```jsx filename="app/admin/page.js" switcher
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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export default async function AdminPage() {
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const session = await verifySession()
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// Check if the user has the 'admin' role
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if (session.role !== 'admin') {
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forbidden()
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}
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// Render the admin page for authorized users
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return <></>
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}
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```
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## Good to know
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- The `forbidden` function cannot be called in the [root layout](/docs/app/api-reference/file-conventions/layout#root-layout).
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- You do not need to write `return forbidden()`. It throws (its TypeScript [`never`](https://www.typescriptlang.org/docs/handbook/2/functions.html#never) return type), so execution stops. A `try/catch` around the call suppresses the interrupt and no forbidden UI renders. Use [`unstable_rethrow`](/docs/app/api-reference/functions/unstable_rethrow) to let it through.
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- A `forbidden()` left in an un-awaited promise throws where nothing catches it, so no forbidden UI renders. In development the server logs `⨯ unhandledRejection: NEXT_HTTP_ERROR_FALLBACK;403`. Always `await` the function that may call it.
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## Examples
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### Calling `forbidden()` after streaming has started
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To keep the page's shell and loading UI visible while the session is checked, put the role check in the [Data Access Layer](/docs/app/guides/authentication#creating-a-data-access-layer-dal) function that loads the data, and render it in a component wrapped in [`<Suspense>`](https://react.dev/reference/react/Suspense). The check runs inside the boundary, so the shell streams while the session resolves:
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```tsx filename="app/projects/page.tsx" switcher highlight={8}
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import { Suspense } from 'react'
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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async function getProjects() {
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const session = await verifySession()
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if (session?.role !== 'admin') {
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forbidden()
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}
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return db.projects.findMany()
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}
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async function Projects() {
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const projects = await getProjects()
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return (
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<ul>
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{projects.map((project) => (
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<li key={project.id}>{project.name}</li>
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))}
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</ul>
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)
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}
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export default function ProjectsPage() {
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return (
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<main>
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<h1>Projects</h1>
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<Suspense fallback={<p>Loading...</p>}>
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<Projects />
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</Suspense>
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</main>
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)
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}
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```
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```jsx filename="app/projects/page.js" switcher highlight={8}
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import { Suspense } from 'react'
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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async function getProjects() {
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const session = await verifySession()
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if (session?.role !== 'admin') {
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forbidden()
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}
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return db.projects.findMany()
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}
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async function Projects() {
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const projects = await getProjects()
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return (
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<ul>
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{projects.map((project) => (
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<li key={project.id}>{project.name}</li>
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))}
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</ul>
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)
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}
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export default function ProjectsPage() {
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return (
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<main>
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<h1>Projects</h1>
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<Suspense fallback={<p>Loading...</p>}>
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<Projects />
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</Suspense>
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</main>
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)
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}
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```
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When the session lacks access, `getProjects` calls `forbidden()`, which throws. Because this happens during rendering, the exception propagates to the nearest [`forbidden`](/docs/app/api-reference/file-conventions/forbidden) boundary, which renders in place of the streamed-in content, even though the page shell has already been sent.
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Add a `forbidden.tsx` alongside the route to define that UI:
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```tsx filename="app/projects/forbidden.tsx" switcher
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export default function Forbidden() {
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return (
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<main>
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<h1>403 - Forbidden</h1>
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<p>You don't have access to this page.</p>
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</main>
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)
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}
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```
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```jsx filename="app/projects/forbidden.js" switcher
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export default function Forbidden() {
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return (
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<main>
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<h1>403 - Forbidden</h1>
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<p>You don't have access to this page.</p>
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</main>
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)
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}
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```
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The trade-off is the HTTP status code. Because the check runs inside the `<Suspense>` boundary, the response has already begun streaming as a `200`, and the status can't change once streaming has started. This is usually fine for a page, where the user sees the `forbidden` UI regardless. To return a real `403` status, the check has to run before the response streams. With [Cache Components](/docs/app/getting-started/caching), every dynamic route streams a static shell first, so run that check in [`proxy`](/docs/app/api-reference/file-conventions/proxy) instead. See [Status codes](/docs/app/api-reference/file-conventions/loading#status-codes).
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### Role-based route protection
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You can use `forbidden` to restrict access to certain routes based on user roles. This ensures that users who are authenticated but lack the required permissions cannot access the route.
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```tsx filename="app/admin/page.tsx" switcher
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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export default async function AdminPage() {
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const session = await verifySession()
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// Check if the user has the 'admin' role
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if (session.role !== 'admin') {
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forbidden()
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}
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// Render the admin page for authorized users
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return (
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<main>
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<h1>Admin Dashboard</h1>
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<p>Welcome, {session.user.name}!</p>
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</main>
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)
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}
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```
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```jsx filename="app/admin/page.js" switcher
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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export default async function AdminPage() {
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const session = await verifySession()
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// Check if the user has the 'admin' role
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if (session.role !== 'admin') {
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forbidden()
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}
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// Render the admin page for authorized users
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return (
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<main>
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<h1>Admin Dashboard</h1>
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<p>Welcome, {session.user.name}!</p>
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</main>
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)
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}
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```
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### Mutations with Server Actions
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When implementing mutations in Server Actions, you can use `forbidden` to only allow users with a specific role to update sensitive data.
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```ts filename="app/actions/update-role.ts" switcher
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'use server'
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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import db from '@/app/lib/db'
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export async function updateRole(formData: FormData) {
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const session = await verifySession()
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// Ensure only admins can update roles
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if (session.role !== 'admin') {
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forbidden()
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}
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// Perform the role update for authorized users
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// ...
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}
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```
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```js filename="app/actions/update-role.js" switcher
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'use server'
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import { verifySession } from '@/app/lib/dal'
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import { forbidden } from 'next/navigation'
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import db from '@/app/lib/db'
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export async function updateRole(formData) {
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const session = await verifySession()
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// Ensure only admins can update roles
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if (session.role !== 'admin') {
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forbidden()
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}
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// Perform the role update for authorized users
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// ...
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}
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```
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## Version History
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| Version | Changes |
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| --------- | ----------------------- |
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| `v15.1.0` | `forbidden` introduced. |
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