ruby 46 lines · 1 tab

Structured JSON error responses

Alex Kumar Jan 2026

1 tab

module ApiErrorHandler
  extend ActiveSupport::Concern

  included do
    rescue_from StandardError, with: :handle_standard_error
    rescue_from ActiveRecord::RecordNotFound, with: :handle_not_found
    rescue_from ActiveRecord::RecordInvalid, with: :handle_validation_error
    rescue_from Api::UnauthorizedError, with: :handle_unauthorized
  end

  private

  def handle_standard_error(exception)
    Rails.logger.error("#{exception.class}: #{exception.message}\n#{exception.backtrace.join("\n")}")
    render json: {
      error: 'INTERNAL_SERVER_ERROR',
      message: 'An unexpected error occurred',
      request_id: request.request_id
    }, status: :internal_server_error
  end

  def handle_not_found(exception)
    render json: {
      error: 'NOT_FOUND',
      message: exception.message,
      request_id: request.request_id
    }, status: :not_found
  end

  def handle_validation_error(exception)
    render json: {
      error: 'VALIDATION_ERROR',
      message: 'Validation failed',
      details: exception.record.errors.as_json,
      request_id: request.request_id
    }, status: :unprocessable_entity
  end

  def handle_unauthorized(exception)
    render json: {
      error: 'UNAUTHORIZED',
      message: exception.message,
      request_id: request.request_id
    }, status: :unauthorized
  end
end

1 file · ruby Explain with highlit

Consistent error handling transforms debugging from guesswork into systematic troubleshooting. I use a rescue handler that catches exceptions globally and transforms them into a standard JSON structure containing an error code, human-readable message, and optional details hash for validation failures. This pattern ensures every API response follows the same contract regardless of which layer raised the exception. I also include a request_id in error responses so clients can reference specific failures when reporting issues. For production systems, I log the full exception with backtrace server-side while returning sanitized messages to clients to avoid leaking implementation details. Custom exception classes like Api::UnauthorizedError map to specific HTTP status codes.

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