docs: @SuppressWarnings("unchecked")
      public void loadCache() {
          if (!cacheManager.isNeedPersist()) {
              return;
          }
          File file = getSaveFile();
          if (null == file) {
              return;
          }
          if (!file.exists()) {
              return;
          }
          BufferedInputStream bis = null;
          try {
              FileInputStream fis = new FileInputStream(file);
              bis = new BufferedInputStream(fis);
              ByteArrayOutputStream baos = new ByteArrayOutputStream();
              byte buf[] = new byte[1024];
              int len = -1;
              while ((len = bis.read(buf)) != -1) {
                  baos.write(buf, 0, len);
              }
              byte retArr[] = baos.toByteArray();
              Object obj = getPersistSerializer().deserialize(retArr, null);
              if (null != obj && obj instanceof ConcurrentHashMap) {
                  cacheManager.getCache().putAll((ConcurrentHashMap<String, Object>) obj);
              }
          } catch (Exception ex) {
              logger.error(ex.getMessage(), ex);
          } finally {
              if (null != bis) {
                  try {
                      bis.close();
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
          }
  
      }