temp.txt

RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(new ByteArrayHttpMessageConverter());

    HttpHeaders headers = new HttpHeaders();
    //headers.add("Authorization", "Bearer SOME_BEARER_TOKEN"); //if requires some token
    headers.setAccept(Arrays.asList(MediaType.APPLICATION_PDF));

    HttpEntity<String> entity = new HttpEntity<>(headers);

    try {
        ResponseEntity<Resource> response = restTemplate.exchange(
                "https://SOME_API.COM/api/docs/12345",
                HttpMethod.GET, entity, Resource.class);


        if (response.getStatusCode() == HttpStatus.OK) {
            String disposition =  response.getHeaders().get("Content-Disposition").get(0);
            String fileName = disposition.replaceFirst("(?i)^.*filename=\"?([^\"]+)\"?.*$", "$1");//get the filename from the Content-Disposition header
            fileName = URLDecoder.decode(fileName, String.valueOf(StandardCharsets.ISO_8859_1));

            //save to examine file
            File targetFile = new File("c:/temp/" + fileName);
            FileUtils.copyInputStreamToFile(response.getBody().getInputStream(), targetFile);
        }
    } catch (RestClientException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }