JavaはURLに基づいて画像をローカルにダウンロードすることを実現する

@GetMapping(value="/download")
public Map,Object> downloadFile( HttpServletResponse response){
    byte[] buffer= new byte[1024];
    int len=-1;
    // httpClient 
    CloseableHttpClient httpClient=HttpClients.createDefault();
    // httpGet 
    HttpGet httpGet=new HttpGet("https://image.baidu.com/test.jpg");
    // 
    try(CloseableHttpResponse httpResponse=httpClient.execute(httpGet);
        InputStream input=httpResponse.getEntity().getContent();
        OutputStream output=response.getOutputStream();
    ){
        // 
        response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(new Date().getTime()+".jpg", "UTF-8"));       // 
        while((len=input.read(buffer))!=-1){
            // buffer ， 0 len, write(buffer); 
            output.write(buffer,0,len);
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}