express-api-problem

Automatically turns your thrown exceptions to the JSON response while conforming to API problem specification

An express package that lets you handle the API problems with ease. It provides a straightforward implementation of IETF Problem Specification and turns your thrown exceptions to be returned in the below format with the header of content type set to application/problem+json

{
   "status": 403,
   "type": "http://example.com/problems/out-of-credit",
   "title": "You do not have enough credit.",
   "detail": "Your current balance is 30, but the item costs 50.",
   "instance": "http://example.net/account/12345/logs?id=233"
}

Where

• title is the summary of problem
• status is the status code
• detail is human readable explanation specific to problem
• type is the absolute URI that identifies the type of problem
• instance is the absolute URI that identifies the specific occurrence of the problem

Installation

yarn add express-api-problem

Usage

Register the middleware

var ApiProblemHandler = require('express-api-problem/middleware');
 
app.use(ApiProblemHandler);

Throw exceptions while instantiating ApiProblem having the following signature

var ApiProblem = require('express-api-problem');
 
// statusCode : HTTP status code to be returned
// title : Title in response
// description : Description of the exception
// additionalDetail : Object having any additional detail that you may want to send
throw new ApiProblem(statusCode, title, description, additionalDetail);

Add the mongoose plugin to automatically transform your model validation errors to API Problem

var mongooseValidator = require('express-api-problem/mongoose-validator');
 
// Will transform any validation exceptions thrown by your model to
//
//  {
//     status: 422,
//     title: "Validation Failed",
//     detail: [
//        {
//          field: "title",
//          message: "Title must be unique"
//        },
//        {
//          field: "expiryDate",
//          message: "Expiry Date must be a valid date"
//        }
//     ]
// }
//
yourSchema.plugin(mongooseValidator);
 
// Also you can modify the status code and title if required
yourSchema.plugin(mongooseValidator, {
    status: 400,
    title: "Look before you submit!"
});
 
// which will result in
//  {
//     status: 400,
//     title: "Look before you submit!",
//     detail: [
//        {
//          field: "title",
//          message: "Title must be unique"
//        },
//        {
//          field: "expiryDate",
//          message: "Expiry Date must be a valid date"
//        }
//     ]
// }

Examples

Throwing exception using only status code

throw new ApiProblem(400);
 
// {
//    status: 400,
//    title: 'Bad Request',
//    type: 'https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html'
// }

Providing description string

throw new ApiProblem(404, 'User not found', 'No user found against the given ID: 10');
 
// {
//    status: 404,
//    title: 'User not found',
//    detail: 'No user found against the given ID: 10',
//    type: 'https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html'
// }

Using object in description

throw new ApiProblem(400, 'Validation failed', {
    name: 'Name field is required',
    email: 'Invalid email given'
});
 
// {
//    status: 422,
//    title: 'Unprocessable entity',
//    detail: {
//      name: ..
//      email: ..
//    },
//    type: 'https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html'
// }

Adding additional detail to response

throw new ApiProblem(400, 'Insufficient Balance', 'You do not have enough balance to purchase the product', {
  available_balance: 'USD 2000',
  required_balance: 'USD 12422'
});
 
// {
//    status: 400,
//    title: 'Insufficient Balance',
//    detail: 'You do not have enough balance to purchase the product',
//    available_balance: 'USD 2000',
//    required_balance: 'USD 12422',
//    type: 'https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html'
// }

Contributing

Feel free to fork, enhance, create PR and lock issues.

License

MIT © Kamran Ahmed