Middy Exception Handler

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#### HTTP exception handler middleware for the middy framework, the stylish Node.js middleware engine for AWS Lambda

Automatically handles any uncaught errors and creates a proper HTTP response for them (using the message and the status code provided by HttpException class).
This exception handler was inspired by Nest.js's built-in exception filters.

This middleware should be set as the last error handler unless you also want to register the http-reponse-serializer. If so, this middleware should come second-last and the http-response-serializer should come last.

This is an alternative to standard Middy error handler with the following differences:

- it contains built in exception classes
- it always returns JSON object and not text
- it handles any uncaught error, not just the ones with statusCode and message

Install

To install this middleware you can use NPM:

``bash

npm install --save middy-exception-handler

`

Options

- logger (defaults to console) - a logging function that is invoked with the current error as an argument. You can pass false if you don't want the logging to happen.
- level (defaults to error) - log level to use for the error log entry

Example

The response argument defines the JSON response body. It can be a string or an object as described below.
The status argument defines the HTTP status code.

`javascript
import middy from '@middy/core';
import { NotFoundException, exceptionHandler } from 'middy-exception-handler';

const handler = middy(() => {
throw new NotFoundException();
});

handler
.use(exceptionHandler());

// when Lambda runs the handler...
handler({}, {}, (_, response) => {
expect(response).toEqual({
statusCode: 404,
body: JSON.stringify({ status: 404, message: 'Not Found' }),
})
})
`

Usage

The HttpException constructor takes two required arguments which determines the response:
- statusCode: defaults to the HTTP status code provided in the status argument
- message: a short description of the HTTP error

$3

- BadGatewayException
- BadRequestException
- ConflictException
- ForbiddenException
- GatewayTimeoutException
- GoneException
- HttpVersionNotSupportedException
- ImATeapotException
- InsufficientSpaceOnResourceException
- InsufficientStorageException
- InternalServerErrorException
- LockedException
- MethodNotAllowedException
- NetworkAuthenticationRequiredException
- NotAcceptableException
- NotFoundException
- NotImplementedException
- PaymentRequiredException
- PreconditionRequiredException
- RequestHeaderFieldsTooLargeException
- RequestTimeoutException
- RequestTooLongException
- RequestURITooLongException
- ServiceUnavailableException
- TooManyRequestsException
- UnauthorizedException
- UnavailableForLegalReasonsException
- UnprocessableEntityException
- UnsupportedMediaTypeException

$3

`javascript
const handler = middy(() => {
throw new UnauthorizedException('A custom message');
});
`

response:
`json
{
"status": 401,
"message": "A custom message"
}
`

$3


`javascript
const handler = middy(() => {
throw new UnauthorizedException('A custom message', { abcd: 'efg' });
});
`

response:
`json
{
"status": 401,
"message": "A custom message",
"details": {
"abcd": "efg"
}
}
`

$3

You can also configure to include a timestamp and exception name to the response:

`javascript
handler
.use(exceptionHandler({ includeTimestamp: true, includeExceptionName: true }));
`

response:
`json
{
"timestamp": "2022-02-04T14:41:22.457Z",
"status": 401,
"exception": "BadRequestException",
"message": "A custom message"
}
``

Contributing

Everyone is very welcome to contribute to this repository. Feel free to raise issues or to submit Pull Requests.