code: public static ClassLoader getCurrentClassLoader() {
          ClassLoader cl = Thread.currentThread().getContextClassLoader();
          if (cl == null) {
              cl = ClassLoaderUtils.class.getClassLoader();
          }
          return cl == null ? ClassLoader.getSystemClassLoader() : cl;
      }
docs: 得到当前ClassLoader，先找线程池的，找不到就找中间件所在的ClassLoader
  
  @return ClassLoader