通过 http 发送 byte[]

Question

I do have get request over http from an angular based client side which expects as an answer an array of bytes from a java server .

angular.ts

  downloadDocument(documentId: string) {
    const params = new HttpParams().set('docId', documentId);
    return this.httpClient.get<any>(`/downloadpdf/`,
      { params: params});
  }

controller.java

     @GetMapping("/downloadpdf")
        public String downloadDocument(@RequestParam("docId") final String docId) {
            String response = (new String(getBytesArray(docId)));
            // getBytesArray returns a byte[]
            // response correctly computed
            return response;
        }

Parsing error is encountered while transmitting over http: "HttpErrorResponse":

• message : 'Http failure during parsing for http://localhost ...'
• error : 'error: SyntaxError: Unexpected token % in JSON at position 0 at JSON.parse () at XMLHttpRequest.onLoad'

Any ideas why this is happening?

Answer 1

It's happening because you call the overload of get() that takes a generic parameter:

this.httpClient.get<any>(...)

This overload sets the response type to JSON, thus telling the HttpClient to parse the response body to JSON and to returned the generated object or array. Since you do not want to receive JSON, you must use another overload.

The documentation is your friend.

If you want to receive a Blob, for example, you would use the second overload, documented as returning an Observable<Blob> , and expecting options with responseType: 'blob' .