location.href="https://open.weixin.qq.com/connect/oauth2/authorize?appid=${appid}&redirect_uri=${redirect_uri}&response_type=code&scope=snsapi_base&state=STATE#wechat_redirect";

其中的redirect_uri 地址偶尔有获取到

String code = request.getParameter("code");

String state = request.getParameter("state");

code 和 state为null的情况