NestJs服务搭建步骤记录（四）：异常捕获

1. 新增拦截器模块

 $ nest g filter filter/http-exception
 $ nest g filter filter/any-exception

http-exception.filter.ts: 捕获主动刨错的内容

import {
  ExceptionFilter,
  Catch,
  ArgumentsHost,
  HttpException,
} from "@nestjs/common";
import { Request, Response } from "express";
@Catch(HttpException)
export class HttpExceptionFilter 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();

    // 设置错误信息
    const message = exception.message
      ? exception.message
      : `${status >= 500 ? "Service Error" : "Client Error"}`;
    const errorResponse = {
      data: {},
      message: status == 401 ? "请重新登陆" : message,
      code: status == 401 ? 401 : -1,
    };

    // 设置返回的状态码， 请求头，发送错误信息
    response.status(status);
    response.header("Content-Type", "application/json; charset=utf-8");
    response.send(errorResponse);
  }
}

any-exception.filter： 捕获全部错误

/**
 * 捕获所有异常
 */
import {
  ExceptionFilter,
  Catch,
  ArgumentsHost,
  HttpException,
  HttpStatus,
} from "@nestjs/common";
@Catch()
export class AllExceptionsFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse();
    const request = ctx.getRequest();

    const status =
      exception instanceof HttpException
        ? exception.getStatus()
        : HttpStatus.INTERNAL_SERVER_ERROR;

    response.status(status).json({
      statusCode: status,
      msg: `Service Error: ${exception}`,
    });
  }
}

2. 成功返回体格式化

 $ nest g interceptor interceptor/transform

transform.interceptor.ts: 格式化返回体

import {
  CallHandler,
  ExecutionContext,
  Injectable,
  NestInterceptor,
} from "@nestjs/common";
import { Observable } from "rxjs";
import { map } from "rxjs/operators";
import { Logger } from "../utils/log4js";
@Injectable()
export class TransformInterceptor implements NestInterceptor {
  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
    const req = context.getArgByIndex(1).req;
    return next.handle().pipe(
      map((data) => {
        return {
          data,
          code: 1,
          msg: "请求成功",
        };
      })
    );
  }
}

3. 在main.ts文件中引入

  const app = await NestFactory.create(AppModule);
  ...
  
  //格式化 返回体
  app.useGlobalInterceptors(new TransformInterceptor());
  // 过滤处理 HTTP 异常
  app.useGlobalFilters(new AllExceptionsFilter());
  app.useGlobalFilters(new HttpExceptionFilter());
  
  ...
  await app.listen(listenPort);

5. 使用：错误提示直接抛错就可以了，正常接口 直接return就可以了

 if (!userInfo) {
      throw new HttpException("用户不存在", 403);
 }