How to use nestjs Logging service

问题:

I tried to use the internal Logger of nestjs (described on https://docs.nestjs.com/techniques/logger -> but with no description of how to use it)

But I had problems (tried to inject LoggerService and so on)

Can anybody explain how to do this?

回答1:

Best practise

Better than accessing the Logger statically is to create an instance for your class:

@Controller()
export class AppController {
  private readonly logger = new Logger(AppController.name);

  @Get()
  async get() {
    this.logger.log('Getting stuff');
  }
}

---

Why is this better?

1) You can provide a context in the constructor like new Logger(AppController.name) so that the class name (or anything else) will be part of all log messages in this class.

2) If you at some point want to extend or replace the default LoggerService, you do not need to change any of your application code besides setting the new logger. Your new logger will automatically be used. If you access it statically it will continue to take the default implementation.

const app = await NestFactory.create(AppModule, {logger: new MyLogger()});

3) You can mock the Logger in your tests:

module.useLogger(new NoOpLogger());

回答2:

You need to import first into your class:

import { Logger } from '@nestjs/common';

and then you can begin with logging:

Logger.log('info')
Logger.warn('warning')
Logger.error('something went wrong! ', error)

回答3:

The answer is simple. There are static methods on the Logger class.

e.g.

static log(message: string, context = '', isTimeDiffEnabled = true) 

Usage:

Logger.log('Only a test');