The backend code:

@GetMapping("datamatrix")
public ResponseEntity<byte[]> generarDataMatrix(Long id) throws IOException {

    byte[] dataMatrixEnBytes = dataMatrix.generarDataMatrixImagen(id.toString(), id);

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.IMAGE_JPEG);
    return new ResponseEntity<>(dataMatrixEnBytes, headers, HttpStatus.OK);
}

In Postman the response is OK:

But in Angular...

Angular Code:

• Service:

generarDataMatrix( articulo: Articulo ): Observable<any> {
  return this.httpClient.get<any>( this.rootUrl   "datamatrix?id="   articulo.id );
}

• Method caller:

generarDataMatrix() {
  this.dbServiceArticulo.generarDataMatrix( this.articuloSeleccionado )
    .subscribe( (res) => {console.log( "res" )});
}

CodePudding user response：

I have done the two solutions that D M has proposed to me and it has worked!

Pretty sure the default Content-Type header is application/json which is why Angular's HttpClient is trying to parse the byte array as JSON. You can set the HttpHeaders for the request manually to the correct Content-Type for the response content. – D M

Otherwise, you could set the responseType to 'blob' for the request: this.httpClient.get(this.rootUrl '...', { responseType: 'blob' });. – D M