Angular 2 download PDF from API and Display it in View

I don't think all of these hacks are necessary. I just did a quick test with the standard http service in angular 2.0, and it worked as expected.

/* generic download mechanism */
public download(url: string, data: Object = null): Observable<Response> {

    //if custom headers are required, add them here
    let headers = new Headers();        

    //add search parameters, if any
    let params = new URLSearchParams();
    if (data) {
        for (let key in data) {
            params.set(key, data[key]);
        }
    }

    //create an instance of requestOptions 
    let requestOptions = new RequestOptions({
        headers: headers,
        search: params
    });

    //any other requestOptions
    requestOptions.method = RequestMethod.Get;
    requestOptions.url = url;
    requestOptions.responseType = ResponseContentType.Blob;

    //create a generic request object with the above requestOptions
    let request = new Request(requestOptions);

    //get the file
    return this.http.request(request)
        .catch(err => {
            /* handle errors */
        });      
}


/* downloads a csv report file generated on the server based on search criteria specified. Save using fileSaver.js. */
downloadSomethingSpecifc(searchCriteria: SearchCriteria): void {

    download(this.url, searchCriteria) 
        .subscribe(
            response => {                                
                let file = response.blob();
                console.log(file.size + " bytes file downloaded. File type: ", file.type);                
                saveAs(file, 'myCSV_Report.csv');
            },
            error => { /* handle errors */ }
        );
}

In fact, this feature isn't implemented yet in the HTTP support.

As a workaround, you need to extend the BrowserXhr class of Angular2 as described below to set the responseType to blob on the underlying xhr object:

import {Injectable} from 'angular2/core';
import {BrowserXhr} from 'angular2/http';

@Injectable()
export class CustomBrowserXhr extends BrowserXhr {
  constructor() {}
  build(): any {
    let xhr = super.build();
    xhr.responseType = "blob";
    return <any>(xhr);
  }
}

Then you need to wrap the response payload into a Blob object and use the FileSaver library to open the download dialog:

downloadFile() {
  this.http.get(
    'https://mapapi.apispark.net/v1/images/Granizo.pdf').subscribe(
      (response) => {
        var mediaType = 'application/pdf';
        var blob = new Blob([response._body], {type: mediaType});
        var filename = 'test.pdf';
        saveAs(blob, filename);
      });
}

The FileSaver library must be included into your HTML file:

<script src="https://cdnjs.cloudflare.com/ajax/libs/FileSaver.js/2014-11-29/FileSaver.min.js"></script>

See this plunkr: http://plnkr.co/edit/tfpS9k2YOO1bMgXBky5Y?p=preview

Unfortunately this will set the responseType for all AJAX requests. To be able to set the value of this property, there are more updates to do in the XHRConnection and Http classes.

As references see these links:

  • Download pdf file using jquery ajax
  • Receive zip file, angularJs

Edit

After thinking a bit more, I think that you could leverage hierarchical injectors and configure this provider only at the level of the component that executes the download:

@Component({
  selector: 'download',
  template: '<div (click)="downloadFile() ">Download</div>'
  , providers: [
    provide(CustomBrowserXhr, 
      { useClass: CustomBrowserXhr }
  ]
})
export class DownloadComponent {
  @Input()
  filename:string;

  constructor(private http:Http) {
  }

  downloadFile() {
    this.http.get(
      'https://mapapi.apispark.net/v1/images/'+this.filename).subscribe(
        (response) => {
          var mediaType = 'application/pdf';
          var blob = new Blob([response._body], {type: mediaType});
          var filename = 'test.pdf';
          saveAs(blob, filename);
        });
    }
}

This override would only applies for this component (don't forget to remove the corresponding provide when bootstrapping your application). The download component could be used like that:

@Component({
  selector: 'somecomponent',
  template: `
    <download filename="'Granizo.pdf'"></download>
  `
  , directives: [ DownloadComponent ]
})

Here is the simplest way to download a file from an API that I was able to come up with. 

import { Injectable } from '@angular/core';
import { Http, ResponseContentType } from "@angular/http";

import * as FileSaver from 'file-saver';

@Injectable()
export class FileDownloadService {


    constructor(private http: Http) { }

    downloadFile(api: string, fileName: string) {
        this.http.get(api, { responseType: 'blob' })
            .subscribe((file: Blob) => {
               FileSaver.saveAs(file, fileName);
        });    
    }

}

Call the downloadFile(api,fileName) method from your component class.

To get FileSaver run the following commands in your terminal 

npm install file-saver --save
npm install @types/file-saver --save

So here is how I managed to get it to work. My situation: I needed to download a PDF from my API endpoint, and save the result as a PDF in the browser.

To support file-saving in all browsers, I used the FileSaver.js module.

I created a component that takes the ID of the file to download as parameter. The component, , is called like this:

<pdf-downloader no="24234232"></pdf-downloader>

The component itself uses XHR to fetch/save the file with the number given in the no parameter. This way we can circumvent the fact that the Angular2 http module doesn't yet support binary result types.

And now, without further ado, the component code:

    import {Component,Input } from 'angular2/core';
    import {BrowserXhr} from 'angular2/http';

    // Use Filesaver.js to save binary to file
    // https://github.com/eligrey/FileSaver.js/
    let fileSaver = require('filesaver.js');


    @Component({
      selector: 'pdf-downloader',
      template: `
        <button
           class="btn btn-secondary-outline btn-sm "
          (click)="download()">
            <span class="fa fa-download" *ngIf="!pending"></span>
            <span class="fa fa-refresh fa-spin" *ngIf="pending"></span>
        </button>
        `
   })

   export class PdfDownloader  {

       @Input() no: any;

       public pending:boolean = false;

       constructor() {}

       public download() {

        // Xhr creates new context so we need to create reference to this
        let self = this;

        // Status flag used in the template.
        this.pending = true;

        // Create the Xhr request object
        let xhr = new XMLHttpRequest();
        let url =  `/api/pdf/iticket/${this.no}?lang=en`;
        xhr.open('GET', url, true);
        xhr.responseType = 'blob';

        // Xhr callback when we get a result back
        // We are not using arrow function because we need the 'this' context
        xhr.onreadystatechange = function() {

            // We use setTimeout to trigger change detection in Zones
            setTimeout( () => { self.pending = false; }, 0);

            // If we get an HTTP status OK (200), save the file using fileSaver
            if(xhr.readyState === 4 && xhr.status === 200) {
                var blob = new Blob([this.response], {type: 'application/pdf'});
                fileSaver.saveAs(blob, 'Report.pdf');
            }
        };

        // Start the Ajax request
        xhr.send();
    }
}

I've used Font Awesome for the fonts used in the template. I wanted the component to display a download button and a spinner while the pdf is fetched.

Also, notice I could use require to fetch the fileSaver.js module. This is because I'm using WebPack so I can require/import like I want. Your syntax might be different depending of your build tool.

Tags:

Pdf

Angular

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