Error Handling and Exceptions

Good error handling improves API reliability and developer experience.

Why it matters

  • Return clear error messages
  • Prevent unhandled crashes
  • Keep proper HTTP status codes
  • Make debugging easier

Basic approach with try/catch

@Get('/:id')
async getOne(@Param('id') id: string) {
  try {
    const userId = parseInt(id);
    if (isNaN(userId)) {
      return { success: false, message: 'ID must be a number' };
    }


    const user = await this.userService.getUserById(userId);
    if (!user) {
      return { success: false, message: 'User not found' };
    }


    return { success: true, data: user };
  } catch (error) {
    return {
      success: false,
      message: 'Internal server error',
      error: error.message,
    };
  }
}

Throw HTTP errors with MidwayHttpError

import { MidwayHttpError } from '@midwayjs/core';


if (isNaN(userId)) {
  throw new MidwayHttpError('ID must be a number', 400);
}


if (!user) {
  throw new MidwayHttpError('User not found', 404);
}

Common status codes

CodeMeaningTypical use
400Bad RequestInvalid parameters
401UnauthorizedNot authenticated
403ForbiddenNo permission
404Not FoundResource missing
500Internal Server ErrorUnexpected server error

Custom error classes

import { MidwayHttpError } from '@midwayjs/core';


export class BusinessError extends MidwayHttpError {
  constructor(message: string, code?: string) {
    super(message, 400);
    this.code = code || 'BUSINESS_ERROR';
  }
  code: string;
}


export class NotFoundError extends MidwayHttpError {
  constructor(resource: string) {
    super(`${resource} not found`, 404);
  }
}

Summary

  • Validate input early
  • Throw meaningful HTTP errors
  • Keep response format consistent
  • Centralize handling with filters/middleware when possible
Handle POST Requests
Middleware Basics
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