public class HttpURLConnectionUtil {
// 通過get請求得到讀取器響應(yīng)數(shù)據(jù)的數(shù)據(jù)流
public static InputStream getInputStreamByGet(String url) {
  try {
    HttpURLConnection conn = (HttpURLConnection) new URL(url)
        .openConnection();
    conn.setReadTimeout(5000);
    conn.setConnectTimeout(5000);
    conn.setRequestMethod("GET");
    if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
      InputStream inputStream = conn.getInputStream();
      return inputStream;
    }
  } catch (IOException e) {
    e.printStackTrace();
  }
  return null;
}
// 將服務(wù)器響應(yīng)的數(shù)據(jù)流存到本地文件
public static void saveData(InputStream is, File file) {
  try (BufferedInputStream bis = new BufferedInputStream(is);
     BufferedOutputStream bos = new BufferedOutputStream(
         new FileOutputStream(file));) {
    byte[] buffer = new byte[1024];
    int len = -1;
    while ((len = bis.read(buffer)) != -1) {
      bos.write(buffer, 0, len);
      bos.flush();
    }
  } catch (IOException e) {
    e.printStackTrace();
  }
}
}

Set<String> imgNumber = (Set<String>) redisTemplate.opsForHash().keys(MAP_KEY);
imgNumber.stream().forEach(e->{
        String url = (String) redisTemplate.opsForHash().get(MAP_KEY,e);
        String fileName = e+".jpg";
        File file = new File("E:\\pdf圖片\\", fileName);

        InputStream inputStream = HttpURLConnectionUtil
            .getInputStreamByGet(url);
        HttpURLConnectionUtil.saveData(inputStream, file);
});