@betsys-nestjs/exception-handling

Exception Handling Library

Library serves for handling of exceptions based on communication type (HTTP, GRPC)

Dependencies

Package	Version
@grpc/grpc-js	^1.8.0
@betsys-nestjs/logger	^5.0.0
@nestjs/common	^10.0.0
@nestjs/config	^3.0.0
@nestjs/core	^10.0.0
@nestjs/microservices	^10.0.0
express	^4.0.0
reflect-metadata	^0.1.12
rxjs	^7.1.0
class-validator	^0.13.2
class-transformer	^0.5.1

Usage

To start using this library simply import ExceptionHandlingModule and use it like this:

ExceptionHandlingModule has method with this signature forRoot('express' | 'grpc')

import {ExceptionHandlingModule} from '@betsys-nestjs/exception-handling'
import {Module} from "@nestjs/common";

@Module({
    imports: [
        ExceptionHandlingModule.forRoot('http')
    ]
})
class AppModule {
}

The signature of exceptions is always the same and looks like this:

{
  "errors": [
    {
      "code": "code",
      "message": "message"
    }
  ]
}

There are 3 different exception types that we distinguish between:

• DomainException - An exception that extends BaseDomainException from this library.
• RequestValidationException - An exception which is mapped from the exceptions thrown by class-validator library.
• All other exceptions - Any other thrown exceptions

Each exception also provides automatic logging, but it's required to initialize the LoggingModule like this:

import {LoggerModule} from "@betsys-nestjs/logger";

LoggerModule.forRoot('http', [])

This bootstraps Logger library globally and is used by ExceptionHandling library automatically.

1. DomainException

Domain exception is thrown within an application and must extend BaseDomainException.

Commonly domain exception is mapped to HttpException within an application controller, we do it automatically via the decorator UseDomainExceptionMapper which specifies the mappings from domain exceptions to http exceptions. You can define any amount of exception mappings. This decorator can be used on either the level of a controller or a specific endpoint within the controller.

Usage example:

import {
    UseDomainExceptionMapper,
    HttpExceptionInterface,
    BaseDomainException
} from '@betsys-nestjs/exception-handling';
import {Controller, Get} from "@nestjs/common";

class TestDomainException extends BaseDomainException {
    static create(): TestDomainException {
        return new TestDomainException(`Domain exception thrown.`);
    }
}

@Controller()
class TestController {
    @UseDomainExceptionMapper<HttpExceptionInterface>(
        'http',
        new Map<string, HttpExceptionInterface>([
            [
                TestDomainException.name,
                {
                    message: 'Test domain exception message',
                    code: 'TEST_DOMAIN_EXCEPTION',
                    statusCode: HttpStatus.CONFLICT,
                },
            ],
        ])
    )
    @Get('domain-exception')
    async testDomainException(): Promise<void> {
        throw TestDomainException.create();
    }
}

2. RequestValidationException

Commonly exceptions thrown by class-validator look like this:

{
  "statusCode": 400,
  "error": "Bad Request",
  "message": [
    "email must be an email"
  ]
}

Using this library you will get more readable exception interface defined above.

Usage example:

import {IsString, IsInt} from 'class-validator';
import {Body, Controller, Get} from "@nestjs/common";

class RequestDto {
    @IsString()
    name!: string;

    @IsInt()
    age!: number;
}

@Controller('test')
export class TestController {
    @Get('validation-exception')
    async testValidationException(@Body() dto: RequestDto): Promise<void> {
    }
}

3. LogicException

All other native exceptions thrown within an application will are caught as logic exceptions. They are always mapped to this HttpException with http status of 500:

{
  "errors": [
    {
      "code": "INTERNAL_SERVER_ERROR",
      "message": "Internal server error"
    }
  ]
}

Usage example:

import {Controller, Get} from "@nestjs/common";

@Controller('test')
export class TestController {
    @Get('logic-exception')
    async testLogicException(): Promise<void> {
        throw new Error('Error');
    }
}