1.开放平台绑定了公众号，获取不到unionid

2.调用https://api.weixin.qq.com/sns/oauth2/access_token?appid=" + appId + "&secret=" + appSecret + "&code=" + code + "&grant_type=authorization_code"

3.返回参数没有unionid

access_token: {"access_token":"jovn4WmjPiH","expires_in":7200,"refresh_token":"J0","openid":"oepz","scope":"snsapi_base"}