## Overview

⚠️ This is LEGACY documentation for a feature that is no longer encouraged to be used. If starting a new app or thinking of implementing a new adapter, consider writing a Handler instead to be used with the RequestManager

An `AdapterError` is used by an adapter to signal that an error occurred during a request to an external API. It indicates a generic error, and subclasses are used to indicate specific error states. To create a custom error to signal a specific error state in communicating with an external API, extend the `AdapterError`. For example, if the external API exclusively used HTTP `503 Service Unavailable` to indicate it was closed for maintenance: ```js {data-filename=app/adapters/maintenance-error.js} import AdapterError from '@ember-data/adapter/error'; export default AdapterError.extend({ message: "Down for maintenance." }); ``` This error would then be returned by an adapter's `handleResponse` method: ```js {data-filename=app/adapters/application.js} import JSONAPIAdapter from '@ember-data/adapter/json-api'; import MaintenanceError from './maintenance-error'; export default class ApplicationAdapter extends JSONAPIAdapter { handleResponse(status) { if (503 === status) { return new MaintenanceError(); } return super.handleResponse(...arguments); } } ``` And can then be detected in an application and used to send the user to an `under-maintenance` route: ```js {data-filename=app/routes/application.js} import Route from '@ember/routing/route'; import MaintenanceError from '../adapters/maintenance-error'; export default class ApplicationRoute extends Route { actions: { error(error, transition) { if (error instanceof MaintenanceError) { this.transitionTo('under-maintenance'); return; } // ...other error handling logic } } } ```

Class ServerError