code: public static SnsToken oauth2ComponentAccessToken(String appid,String code,String component_appid,String component_access_token ){
  		HttpUriRequest httpUriRequest = RequestBuilder.post()
  				.setUri(BASE_URI + "/sns/oauth2/component/access_token")
  				.addParameter("appid", appid)
  				.addParameter("code", code)
  				.addParameter("grant_type", "authorization_code")
  				.addParameter("component_appid", component_appid)
  				.addParameter("component_access_token", component_access_token)
  				.build();
  		return LocalHttpClient.executeJsonResult(httpUriRequest,SnsToken.class);
  	}
docs: 通过code换取网页授权access_token (第三方平台开发)
  @param appid appid
  @param code code
  @param component_appid 服务开发方的appid
  @param component_access_token 服务开发方的access_token
  @return SnsToken