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| # node 日志 | ||
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| ## nest 中是如何打印日志的 | ||
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| ```ts | ||
| import { ConsoleLogger, Controller, Get, Logger } from '@nestjs/common'; | ||
| import { AppService } from './app.service'; | ||
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| @Controller() | ||
| export class AppController { | ||
| private logger = new Logger(); | ||
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| constructor(private readonly appService: AppService) {} | ||
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| @Get() | ||
| getHello(): string { | ||
| this.logger.debug('aaa', AppController.name); | ||
| this.logger.error('bbb', AppController.name); | ||
| this.logger.log('ccc', AppController.name); | ||
| this.logger.verbose('ddd', AppController.name); | ||
| this.logger.warn('eee', AppController.name); | ||
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| return this.appService.getHello(); | ||
| } | ||
| } | ||
| ``` | ||
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|  | ||
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| 这里的 `verbose`、`debug`、`log`、`warn`、`error` 就是日志级别，而 `[]` 中的是 `context`，也就是当前所在的上下文，最后是日志的内容。 | ||
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| 这个日志是受 `nest` 控制的，可以在创建应用的时候指定是否开启，设置为 `false` 之后就没有日志了： | ||
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|  | ||
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|  | ||
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| 也可以自己决定输出什么级别的日志： | ||
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|  | ||
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| 此外，你还可以自定义日志打印的方式，定义一个实现 LoggerService 接口的类： | ||
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| ```ts | ||
| import { LoggerService, LogLevel } from '@nestjs/common'; | ||
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| export class MyLogger implements LoggerService { | ||
| log(message: string, context: string) { | ||
| console.log(`---log---[${context}]---`, message) | ||
| } | ||
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| error(message: string, context: string) { | ||
| console.log(`---error---[${context}]---`, message) | ||
| } | ||
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| warn(message: string, context: string) { | ||
| console.log(`---warn---[${context}]---`, message) | ||
| } | ||
| } | ||
| ``` | ||
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| 在创建应用时指定这个 logger： | ||
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|  | ||
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| 也可以不自己实现 LoggerService 的全部方法，而是继承 ConsoleLogger，重写一些方法： | ||
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| ```ts | ||
| import { ConsoleLogger } from '@nestjs/common'; | ||
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| export class MyLogger2 extends ConsoleLogger{ | ||
| log(message: string, context: string) { | ||
| console.log(`[${context}]`,message) | ||
| } | ||
| } | ||
| ``` |