属性映射不存在于类型'可观察的'

Question

我想使用以下代码实现文件下载：

RestAPI：

@GetMapping("export")
    public ResponseEntity<InputStreamResource> export() throws IOException {
        ClassPathResource pdfFile = new ClassPathResource(EXTERNAL_FILE_PATH);

        HttpHeaders headers = new HttpHeaders();
        headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
        headers.add("Pragma", "no-cache");
        headers.add("Expires", "0");

        return ResponseEntity.ok().headers(headers).contentLength(pdfFile.contentLength())
                .contentType(MediaType.parseMediaType("application/pdf"))
                .body(new InputStreamResource(pdfFile.getInputStream()));
    }

服务：

import {Injectable} from '@angular/core';
import {HttpClient, HttpParams} from "@angular/common/http";
import {Observable} from "rxjs/index";
import {environment} from "../../../environments/environment";
import {HttpUtils} from "../common/http-utils";
import { map } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})
export class DownloadService {

  constructor(private http: HttpClient) {
  }

  downloadPDF(): any {
    return this.http.get(environment.api.urls.downloads.getPdf, { responseType: 'blob' }).map(
    (res) => {
        return new Blob([res.blob()], { type: 'application/pdf' });
    });
  }  
}

组件：

import {Component, OnInit} from '@angular/core';
import {DownloadService} from "../service/download.service";
import {ActivatedRoute, Router} from "@angular/router";
import {flatMap} from "rxjs/internal/operators";
import {of} from "rxjs/index";
import { map } from 'rxjs/operators';

@Component({
  selector: 'app-download',
  templateUrl: './download.component.html',
  styleUrls: ['./download.component.scss']
})
export class DownloadComponent implements OnInit {

  constructor(private downloadService: DownloadService,
              private router: Router,
              private route: ActivatedRoute) {
  }

  ngOnInit() {   
  }

  export() {               
    this.downloadService.downloadPDF().subscribe(res => {
      const fileURL = URL.createObjectURL(res);
      window.open(fileURL, '_blank');
    });         
  } 
}

当我启动angular时，我得到错误：src/app/panel/service/download中的错误。服务ts（17,91）：错误TS2339:类型“Observable”上不存在属性“map”。

将map导入代码的正确wya是什么？当我点击下载按钮时，什么也没发生。

Answer 1

您可以这样调用请求，因为您使用的是angular 6

downloadPDF(): any {
    return this.http.get(environment.api.urls.downloads.getPdf, { responseType: 'blob' });
  }  

更新：导入响应内容类型

从'@angular/Http'导入{Http，ResponseContentType}；

Answer 2

您可能正在使用Rxjs 5.5或更高版本。

在Rxjs 5.5之后，您不能再直接在可观察值上链接像map这样的运算符。您必须使用。管道，然后传递逗号分隔的运算符列表。

import { map } from 'rxjs/operators';
...
downloadPDF(): any {
  return this.http.get(environment.api.urls.downloads.getPdf, {
    responseType: 'blob',
    observe: 'response'
  })
  .pipe(
    map((res: any) => {
      return new Blob([res.blob()], { type: 'application/pdf' });
    })
  );
}

这是给你裁判的StackBlitz样本。

顺便说一句，资源管理器是一个了不起的工具，可以检查Rxjs语法到目前为止是如何变化的。