typescript - Angular 6 Downloading file from rest api

Question

I have my REST API where I put my pdf file, now I want my angular app to download it on click via my web browser but I got HttpErrorResponse

"Unexpected token % in JSON at position 0"

"SyntaxError: Unexpected token % in JSON at position 0? at JSON.parse (

this is my endpoint

    @GetMapping("/help/pdf2")
public ResponseEntity<InputStreamResource> getPdf2(){

    Resource resource = new ClassPathResource("/pdf-sample.pdf");
    long r = 0;
    InputStream is=null;

    try {
        is = resource.getInputStream();
        r = resource.contentLength();
    } catch (IOException e) {
        e.printStackTrace();
    }

        return ResponseEntity.ok().contentLength(r)
                .contentType(MediaType.parseMediaType("application/pdf"))
                .body(new InputStreamResource(is));

}

this is my service

  getPdf() {

this.authKey = localStorage.getItem('jwt_token');

const httpOptions = {
  headers: new HttpHeaders({
    'Content-Type':  'application/pdf',
    'Authorization' : this.authKey,
    responseType : 'blob',
    Accept : 'application/pdf',
    observe : 'response'
  })
};
return this.http
  .get("http://localhost:9989/api/download/help/pdf2", httpOptions);

}

and invocation

this.downloadService.getPdf()
  .subscribe((resultBlob: Blob) => {
  var downloadURL = URL.createObjectURL(resultBlob);
  window.open(downloadURL);});

Answer 1

I solved the issue in this way (please note that I have merged multiple solutions found on stack overflow, but I cannot find the references. Feel free to add them in the comments).

In My service I have:

public getPDF(): Observable<Blob> {   
//const options = { responseType: 'blob' }; there is no use of this
    let uri = '/my/uri';
    // this.http refers to HttpClient. Note here that you cannot use the generic get<Blob> as it does not compile: instead you "choose" the appropriate API in this way.
    return this.http.get(uri, { responseType: 'blob' });
}

In the component, I have (this is the part merged from multiple answers):

public showPDF(fileName: string): void {
    this.myService.getPDF()
        .subscribe(x => {
            // It is necessary to create a new blob object with mime-type explicitly set
            // otherwise only Chrome works like it should
            var newBlob = new Blob([x], { type: "application/pdf" });
            
            // IE doesn't allow using a blob object directly as link href
            // instead it is necessary to use msSaveOrOpenBlob
            if (window.navigator && window.navigator.msSaveOrOpenBlob) {
                window.navigator.msSaveOrOpenBlob(newBlob, fileName);
                return;
            }
            
            // For other browsers: 
            // Create a link pointing to the ObjectURL containing the blob.
            const data = window.URL.createObjectURL(newBlob);
            
            var link = document.createElement('a');
            link.href = data;
            link.download = fileName;
            // this is necessary as link.click() does not work on the latest firefox
            link.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true, view: window }));
            
            setTimeout(function () {
                // For Firefox it is necessary to delay revoking the ObjectURL
                window.URL.revokeObjectURL(data);
                link.remove();
            }, 100);
        });
}

The code above works in IE, Edge, Chrome and Firefox. However, I don't really like it, as my component is pulluted with browser specific stuff which will surely change over time.