How do you map database and ORM exceptions to HTTP exceptions using a global filter in NestJS?

Q: How do you map database and ORM exceptions to HTTP exceptions using a global filter in NestJS?

import { QueryFailedError, EntityNotFoundError } from 'typeorm'; @Catch() export class OrmExceptionFilter implements ExceptionFilter { private readonly logger = new Logger(OrmExceptionFilter.name); catch(exception: unknown, host: ArgumentsHost): void { const ctx = host.switchToHttp(); const res = ctx.getResponse (); const req = ctx.getRequest (); let status = HttpStatus.INTERNAL_SERVER_ERROR; let message = 'Internal server error'; if (exception instanceof EntityNotFoundError) { status = HttpStatus.NOT_FOUND; message = exception.message; } else if (exception instanceof QueryFailedError) { const code = (exception as any).code; if (code === '23505') { status = HttpStatus.CONFLICT; message = 'Duplicate entry — resource already exists'; } else if (code === '23503') { status = HttpStatus.BAD_REQUEST; message = 'Invalid reference — related resource not found'; } else { this.logger.error('Unhandled DB error', exception.stack); } } else if (exception instanceof HttpException) { status = exception.getStatus(); const b = exception.getResponse(); message = typeof b === 'string' ? b : (b as any).message; } else if (exception instanceof Error) { this.logger.error('Unhandled error', exception.stack); } res.status(status).json({ statusCode: status, message, path: req.url }); } } EntityNotFoundError (TypeORM) — map to 404 Not Found. QueryFailedError code 23505 (Postgres unique violation) — map to 409 Conflict. QueryFailedError code 23503 (Postgres foreign key violation) — map to 400 Bad Request. QueryFailedError code 23502 (Postgres not null violation) — map to 400 Bad Request. Always log unexpected database errors with the full stack — never silently swallow them.

Difficulty: 6/10

Exception handling, NestJS filters, ORM integration

Use @Catch() with no argument to intercept all exceptions including ORM errors. Branch on the exception type to map specific ORM error codes to semantic HTTP status codes — EntityNotFoundError to 404, unique constraint violations (code 23505) to 409, foreign key violations (code 23503) to 400. Log unknown DB errors server-side and return a generic 500.

ORM exception to HTTP exception mapping filter

Common ORM error codes to HTTP status mappings:

1
EntityNotFoundError (TypeORM) — map to 404 Not Found.
2
QueryFailedError code 23505 (Postgres unique violation) — map to 409 Conflict.
3
QueryFailedError code 23503 (Postgres foreign key violation) — map to 400 Bad Request.
4
QueryFailedError code 23502 (Postgres not null violation) — map to 400 Bad Request.
5
Always log unexpected database errors with the full stack — never silently swallow them.

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0-2 years experience

2-5 years experience

How do you map database and ORM exceptions to HTTP exceptions using a global filter in NestJS?

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