NestJS Enterprise Backend APIs · Lección

Gestión de errores e interceptores

Implemente filtros de excepciones personalizados para gestionar los errores correctamente y utilice interceptores para transformar respuestas o registrar solicitudes.

Gestión de errores e interceptores es una lección gratuita de NestJS Enterprise Backend APIs en CoddyKit. Esta es la lección 3 de 3. Puedes leer la lección completa abajo gratuitamente — luego la practicas en el navegador con un editor de código integrado y un tutor de IA 24/7. Forma parte de la ruta de aprendizaje de NestJS Enterprise Backend APIs, y tu progreso se sincroniza en la web y la app de CoddyKit. El curso de NestJS Enterprise Backend APIs incluye 3 lecciones en total.

Partes de esta lección aún no han sido traducidas y se muestran en inglés.

Graceful API Error Handling

When building APIs, it's crucial to handle errors gracefully. Instead of crashing or returning vague messages, your API should provide clear, consistent feedback to clients.

This makes your API user-friendly and helps in debugging both client-side and server-side issues.

NestJS Built-in Exceptions

NestJS provides a set of standard HTTP exceptions, extending from HttpException. These exceptions map directly to common HTTP status codes.

BadRequestException (400)
UnauthorizedException (401)
NotFoundException (404)
InternalServerErrorException (500)

Using these ensures your API speaks the standard HTTP language.

Throwing Built-in Exceptions

You can throw these exceptions directly from your controllers or services. NestJS's built-in exception layer will catch them and automatically format a standardized JSON error response.

Try running this example and access /greet/World (success) and /greet/error (error) to see the difference:

import { NestFactory } from '@nestjs/core';
import { Controller, Get, Param, NotFoundException, Module } from '@nestjs/common';

@Controller('greet')
class GreetController {
  @Get(':name')
  hello(@Param('name') name: string) {
    if (name === 'error') {
      throw new NotFoundException('Name "error" is not allowed!');
    }
    return `Hello, ${name}!`;
  }
}

@Module({
  controllers: [GreetController],
})
class AppModule {}

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
  console.log('App running on http://localhost:3000');
  console.log('Try http://localhost:3000/greet/World');
  console.log('Try http://localhost:3000/greet/error');
}
bootstrap();

Custom Exception Filters

While built-in exceptions are useful, you might need more control over the error response format. This is where custom exception filters come in.

A custom filter lets you catch specific exceptions (or all exceptions) and define exactly what response is sent back to the client, including custom logging or integration with external services.

Building a Custom Filter

To create a custom filter, you implement the ExceptionFilter interface and decorate it with @Catch(), specifying the exception type(s) it should handle. Here's a basic example:

import { ExceptionFilter, Catch, ArgumentsHost, HttpException, HttpStatus } from '@nestjs/common';
import { Request, Response } from 'express';

@Catch(HttpException)
export class CustomHttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    const request = ctx.getRequest<Request>();
    const status = exception.getStatus();

    response
      .status(status)
      .json({
        statusCode: status,
        timestamp: new Date().toISOString(),
        path: request.url,
        customMessage: `An error occurred: ${exception.message}`,
      });
  }
}

Applying Custom Filters

Once created, a custom filter needs to be applied. You can apply filters:

Globally: Using app.useGlobalFilters(new MyFilter()) in main.ts.
Controller-scoped: Using @UseFilters(MyFilter) on a controller class.
Method-scoped: Using @UseFilters(MyFilter) on a specific route handler method.

Global filters catch exceptions across your entire application, providing a consistent error structure.

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module'; // Assume AppModule exists
import { CustomHttpExceptionFilter } from './custom-http-exception.filter'; // Assume filter exists

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.useGlobalFilters(new CustomHttpExceptionFilter());
  await app.listen(3000);
}

Introducing Interceptors

Interceptors are another powerful feature in NestJS, inspired by Aspect-Oriented Programming (AOP). They allow you to 'intercept' requests and responses, adding extra logic before or after a route handler executes.

Think of them as hooks into the request-response lifecycle, giving you fine-grained control.

Common Interceptor Uses

Interceptors are incredibly versatile and can be used for various purposes:

Logging: Log request details, execution time, and responses.
Transforming responses: Modify the outgoing data structure (e.g., wrap in a data object).
Caching: Implement response caching for performance.
Binding extra logic: Execute code before/after a method.

Logging Interceptor Example

Here's a simple interceptor that logs the time taken for a request to complete. It uses RxJS operators like tap and finalize to interact with the observable stream.

import { Injectable, NestInterceptor, ExecutionContext, CallHandler } from '@nestjs/common';
import { Observable } from 'rxjs';
import { tap, finalize } from 'rxjs/operators';

@Injectable()
export class LoggingInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
    console.log('Before request...');

    const now = Date.now();
    return next.handle().pipe(
      tap(() => console.log(`After request... ${Date.now() - now}ms`)),
      finalize(() => console.log('Request/response cycle finalized.'))
    );
  }
}

Transforming Responses

Interceptors can also transform the data returned by your route handlers. This is common for standardizing API responses, for example, by wrapping all successful data in a data property to ensure consistency.

import { Injectable, NestInterceptor, ExecutionContext, CallHandler } from '@nestjs/common';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';

interface Response<T> {
  data: T;
}

@Injectable()
export class TransformInterceptor<T> implements NestInterceptor<T, Response<T>> {
  intercept(context: ExecutionContext, next: CallHandler): Observable<Response<T>> {
    return next.handle().pipe(map(data => ({ data })));
  }
}

Quick Check: Error vs Intercept

You've learned about both Exception Filters and Interceptors. Let's test your understanding of their primary roles.

Recap & Next Steps

In this lesson, we covered essential techniques for building robust NestJS APIs:

Graceful Error Handling using built-in HTTP exceptions.
Custom Exception Filters to customize error responses and handle specific exceptions.
Interceptors for logging, transforming responses, and adding cross-cutting concerns.

Mastering these concepts will help you build professional, maintainable, and user-friendly APIs.

Preguntas frecuentes

¿La lección «Gestión de errores e interceptores» es gratis?

Sí — el texto completo de «Gestión de errores e interceptores» es gratis para leer aquí en la web. Para practicarla de forma interactiva (editor de código integrado y tutor de IA 24/7) y desbloquear el resto del curso de NestJS Enterprise Backend APIs, actualiza a CoddyKit PRO. El curso de NestJS Enterprise Backend APIs incluye 3 lecciones en total.

¿Qué aprenderé en «Gestión de errores e interceptores»?

Implemente filtros de excepciones personalizados para gestionar los errores correctamente y utilice interceptores para transformar respuestas o registrar solicitudes. Practicas NestJS Enterprise Backend APIs con código real que ejecutas directamente en el navegador, y un tutor de IA 24/7 responde tus preguntas mientras trabajas en la lección.

¿Necesito experiencia previa para empezar NestJS Enterprise Backend APIs?

No se requiere experiencia previa. NestJS Enterprise Backend APIs en CoddyKit está estructurado para principiantes hasta estudiantes avanzados, así que puedes empezar aquí o desde el inicio y avanzar a tu ritmo. Esta es la lección 3 de 3.

¿Cuánto tiempo toma la lección «Gestión de errores e interceptores»?

La mayoría de las lecciones de CoddyKit toman alrededor de 5–10 minutos. Cada una es compacta e interactiva, así que avanzas constantemente y retomas exactamente por donde dejaste en la web y la app.

¿Puedo escribir y ejecutar código en esta lección de NestJS Enterprise Backend APIs?

Sí. Cada lección de NestJS Enterprise Backend APIs incluye un editor de código integrado, así que escribes y ejecutas código real directamente en tu navegador y obtienes retroalimentación instantánea de IA — sin configuración local necesaria.

Todas las lecciones de este curso

← Volver a NestJS Enterprise Backend APIs