code: public static JarClassLoader load(File dir) {
  		final JarClassLoader loader = new JarClassLoader();
  		loader.addJar(dir);//查找加载所有jar
  		loader.addURL(dir);//查找加载所有class
  		return loader;
  	}
docs: 加载Jar到ClassPath
  
  @param dir jar文件或所在目录
  @return JarClassLoader