为什么nestjs拦截器返回undefined？

Question

我试图在nestjs中实现一个日志记录拦截器，它捕获所有请求和响应并记录它。

因此我实现了像这样的LoggingInterceptor

import { logger } from './../utils/logger';
import { ExecutionContext, Injectable, NestInterceptor } from '@nestjs/common';
import { Observable, BehaviorSubject, from } from 'rxjs';
import { map, tap, refCount, publish, publishLast } from 'rxjs/operators';

    @Injectable()
    export class LoggingInterceptorInterceptor implements NestInterceptor {
      intercept(context: ExecutionContext, call$: Observable<any>): Observable<any> {
        const reqHeaders = context.switchToHttp().getRequest().headers;
        const reqBody = context.switchToHttp().getRequest().body;
        logger.info('Logging the incoming request:',reqHeaders);
        logger.info('Logging the incoming req body:', reqBody);
        const now = Date.now();
        logger.info('Time of request call is', now);

        const serviceBehaviorSubj = new BehaviorSubject<any>(null);

    // response will be available only in the call$ observable stream
    // so use tap to get a clone of the observable and print the data sent

        // this pipe call transforms the response object to start with something called data
        // so a default response like "Done", "test" looks now as a json string 
        // {data : Done}  {data: test}
        // const anotherrespObs: Observable<any> = call$.pipe(publishLast(), refCount());
        // anotherrespObs.pipe(publishLast(), refCount()).subscribe(data => {
        //   logger.info('Logging the outgoing response', data);
        // });

        return call$.pipe(map(data => {
          console.log('data here is', data);
          return ({ dottted: data });
        }));
        //oo.then(return new Pro)
        // return call$.pipe(tap(() => {
        //   logger.info(`Time of completion is ${Date.now() -now}`);
        // }), map(data => {
        //   console.log('ccccccc', data);
        //   return data;
        // }));
      }
}

我理解调用$运算符的行为类似于Observable，并且将由nestjs内部订阅以将响应发送到客户端，但我想在发送之前记录信息并可能转换响应

所以我使用了rxjs的map（）运算符。如果响应集的类型不是'application / json'，则此功能正常。如果Content-Type是'plain / text'，则应用map操作并将其转换为所需的json对象并发送到客户端，但如果响应已经是application / json类型，则不是这样，即json宾语。我无法应用转换对象。在记录发送到map（）的值时，我看到它被记录为json对象的未定义。那么我如何得到响应（即使它是一个json对象）并可能在将它发送到拦截器中的客户端之前将其记录并转换

注意：我警惕响应可能包含敏感信息，但我可能会使用日志屏蔽来屏蔽响应数据，但这目前用于测试目的

这是我能够在拦截器中记录响应的示例控制器

@ApiOperation({ title: 'Get - With Params', description: 'Test Method with parms' })
@Get('/getTest/:id1/:id2')
@ApiOkResponse({ description: 'Sample string is emitted' })
@ApiResponse({ status: 404, description: 'The endpoint is unavailable' })
@ApiResponse({ status: 503, description: 'The endpoint cannot be processed' })
// @Header('sampleHeaderKey', 'sampleHeaderValue')
// NOte if you send params in the URL and do not use @param then the URL will
// result in NO such end point
public getConfigDataInResponse(@Param('id1') id1: number, @Param('id2') id2: number,  @Req() req) {
  logger.info('request headers', req.headers);
  logger.info('reqiest params', req.params);
  logger.info('reqiest query params', req.query);
  logger.info('reqiest body ', req.body);
  return 'TEST';
}

这里是无法记录响应的方法，它在拦截器中是“未定义的”

public getConfigDataInResponse(@Param('id1') id1: number, @Param('id2') id2: number,  @Req() req, @Res() res) {
  logger.info('request headers', req.headers);
  logger.info('reqiest params', req.params);
  logger.info('reqiest query params', req.query);
  logger.info('reqiest body ', req.body);
  res.set('SampeHeader', 'saomevaluie');
  res.status(HttpStatus.OK).send('some data');
}

Answer 1

当你在控制器方法中注入@Res()时，许多使得嵌套如拦截器那么棒的特性将无法工作。

---

在大多数情况下，您不需要注入@Res()，因为您可以使用专用装饰器。在你的例子中将是：

// Sets the http response code (default for POST is 201, for anything else 200)
@HttpCode(204)
// Sets a custom header
@Header('SampleHeader', 'somevalue')
@Get('/getTest/:id1/:id2')
public getConfigDataInResponse(@Param('id1') id1: number, @Param('id2') id2: number) {
  return 'some data';
}