Error Handling Classes

DomusJS provides a set of structured error classes that help you manage predictable failures, especially in the infrastructure and API layers.

✅ These errors are designed for use outside the domain layer — mainly in HTTP controllers, services, and external integrations.
✅ Inside the domain layer, you should use the Result pattern or domain-specific error objects.

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BaseError

All infrastructure errors extend the BaseError class:

export abstract class BaseError extends Error {
  public readonly name: string;
  public readonly code: string;
  public readonly statusCode: number;

  constructor(message: string, code: string, statusCode: number) {
    super(message);
    this.name = this.constructor.name;
    this.code = code;
    this.statusCode = statusCode;
    Error.captureStackTrace(this, this.constructor);
  }
}

✅ Provides a common structure with name, code, and HTTP status.

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Provided Error Classes

🚫 BadRequestError

export class BadRequestError extends BaseError {
  constructor(message = 'Bad request', code = 'BAD_REQUEST') {
    super(message, code, 400);
  }
}

🔒 UnauthorizedError

export class UnauthorizedError extends BaseError {
  constructor(message = 'Unauthorized', code = 'UNAUTHORIZED') {
    super(message, code, 401);
  }
}

❓ NotFoundError

export class NotFoundError extends BaseError {
  constructor(message = 'Resource not found', code = 'NOT_FOUND') {
    super(message, code, 404);
  }
}

✅ These are intended for invalid inputs, authentication failures, or missing resources in the infrastructure layer.

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Built-in Express Error Handler

DomusJS provides a ready-to-use Express middleware called errorHandler that automatically:

✅ Catches thrown BaseError instances.
✅ Logs the error using the registered Logger.
✅ Formats a structured HTTP response.

Usage

import { errorHandler } from '@domusjs/infrastructure';

app.use(errorHandler);

Example Response

{
  "code": "NOT_FOUND",
  "message": "User not found"
}

✅ For unknown or unhandled errors, it returns a 500 Internal Server Error.

Note: This middleware is for the infrastructure and API layer.
Domain-level logic should use the Result pattern or domain-specific error handling.

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Best Practices

✅ Use structured errors to standardize API responses.
✅ Avoid throwing exceptions inside the domain layer — use domain results or notifications.
✅ Centralize error handling using the provided middleware.
✅ Include error codes for better debugging and client feedback.