# ExceptionFiltersContext

**Kind:** Class

**Source:** [`packages/websockets/context/exception-filters-context.ts`](https://github.com/nestjs/nest/blob/master/packages/websockets/context/exception-filters-context.ts#L10)

**Part of:** [Websockets](subsystem-packages-websockets)

`ExceptionFiltersContext` builds and resolves WebSocket exception filters for gateway handlers. It combines method-level and global filter metadata into a `WsExceptionsHandler`, allowing WebSocket errors to be processed consistently through Nest’s exception-filter pipeline.

**Extends:** `BaseExceptionFilterContext`

## Methods

| Method | Signature | Returns |
|---|---|---|
| `create` | `create(instance: object, callback: <TClient>(client: TClient, data: any) => any, moduleKey: string)` | `WsExceptionsHandler` |
| `getGlobalMetadata` | `getGlobalMetadata()` | `T` |

## Where it refuses work

- `ExceptionFiltersContext` stops the work with an early return when `isEmpty(filters)`.

## Diagram

```mermaid
graph LR
  Gateway[WebSocket Gateway Handler] --> Context[ExceptionFiltersContext]
  Context --> Metadata[Exception Filter Metadata]
  Context --> GlobalFilters[Global / Request-Scoped Filters]
  Metadata --> Handler[WsExceptionsHandler]
  GlobalFilters --> Handler
  Handler --> Client[WebSocket Client Error Response]
```

## Usage

```ts
import { ExceptionFiltersContext } from '@nestjs/websockets';
import { NestContainer } from '@nestjs/core';
import { ApplicationConfig } from '@nestjs/core';

const container = new NestContainer();
const applicationConfig = new ApplicationConfig();

const exceptionFiltersContext = new ExceptionFiltersContext(
  container,
  applicationConfig,
);

const wsExceptionsHandler = exceptionFiltersContext.create(
  gatewayInstance,
  gatewayInstance.handleMessage,
  'ChatGatewayModule',
);

// Use the resolved handler when invoking a WebSocket gateway method.
wsExceptionsHandler.handle(
  new Error('Unable to process message'),
  host,
);
```

## AI Coding Instructions

- Use `create()` when preparing a WebSocket gateway callback so method- and class-level exception filters are resolved before execution.
- Preserve filter ordering: custom filters are applied in reverse order to match Nest’s exception-filter execution behavior.
- Use `getGlobalMetadata()` when extending filter resolution logic; it includes configured global filters and request-scoped filters when applicable.
- Avoid bypassing `WsExceptionsHandler` for gateway errors, as doing so can skip custom filters and inconsistent client error serialization.

## How it works

## `ExceptionFiltersContext`

`ExceptionFiltersContext` is a public WebSocket exception-filter context builder. It extends `BaseExceptionFilterContext` and is constructed with a `NestContainer`, which the inherited implementation uses to resolve class-based filters from a module’s injectable collection. [`packages/websockets/context/exception-filters-context.ts:10-13`](packages/websockets/context/exception-filters-context.ts#L10-L13) [`packages/core/exceptions/base-exception-filter-context.ts:14-16`](packages/core/exceptions/base-exception-filter-context.ts#L14-L16) [`packages/core/exceptions/base-exception-filter-context.ts:59-71`](packages/core/exceptions/base-exception-filter-context.ts#L59-L71)

## Relationships

- IMPORTS → `EXCEPTION_FILTERS_METADATA`
- IMPORTS → `isEmpty`
- IMPORTS → `BaseExceptionFilterContext`
- IMPORTS → `NestContainer`