网页端扫码通过公众号实现微信授权登录

1.参考开发文档：

https://developers.weixin.qq.com/doc/offiaccount/OA_Web_Apps/Wechat_webpage_authorization.html#0

2.先调起微信授权页面，获取code。（如果用户同意授权，页面将跳转至 redirect_uri/?code=CODE&state=STATE）。用如下连接生成二维码，微信扫码可以调起授权页面。

https://open.weixin.qq.com/connect/oauth2/authorize?appid=wxbf1f83d35ba69d&redirect_uri=http://www.dd.com.cn&response_type=code&scope=snsapi_userinfo&state=STATE&connect_redirect=1#wechat_redirect

3.用户同意后回调redirect_uri配置的接口，获取code：

https://www.dd.com.cn/?code=001Ut4Ha1yuI3F05mEJa1DlLq64Ut4HG&state=STATE

4.通过access_token接口，传入code，获取到用户的openId，unionid和access_token信息：

https://api.weixin.qq.com/sns/oauth2/access_token?appid=wxbf1f83d3a69d&secret=c28917fc609f3a6f6780b60702ff0d89&code=001Ut4Ha1yuI3F05mEJa1DlLq64Ut4HG&grant_type=authorization_code

{
    "access_token": "67_xtTNGAMFQw6r5HVWajUmw5P1E7L9rTvF6YeFSKZwxMr3RdSww00WoM6y8dGv6rQdVEZAtV8nLtGID0MI4-hM74h0tWD941nYdbSULG46QgI",
    "expires_in": 7200,
    "refresh_token": "67_y1jqaGqpojn2IzVzvGBdGIuH4t_Iy1PLSE_ccR-2_dkz8hOCRpiEMrCfGaY4UP0EDqvQlLJf2wwusjadbetZhUcskk_MlCzhRd-suUckqms",
    "openid": "oFVCr549_IkCU_u46_v0",
    "scope": "snsapi_userinfo",
    "unionid": "oSBoT6StcN2EHswnOunQ0XVx0"
}

5.通过这个接口，传入openId，access_token参数，获取用户的基本信息：

https://api.weixin.qq.com/sns/userinfo?access_token=67_xtTNGAMFQw6r5HVWajUmw5P1E7L9rTvF6YeFSKZwxMr3RdSww00WoM6y8dGv6rQdVEZAtV8nLtGID0MI4-hM74h0tWD941nYdbSULG46QgI&openid=oFVCr549_IvbcT3iZskCU_u46_v0&lang=zh_CN

{
    "openid": "oFVCr549_IT3iZskCU_u46_v0",
    "nickname": "ooo",
    "sex": 0,
    "language": "",
    "city": "",
    "province": "",
    "country": "",
    "headimgurl": "https:\/\/thirdwx.qlogo.cn\/mmopen\/vi_32\/vdR2Ria3VobffzGBi8NZUIEdaiat4fwhzNzURwFQu7K2o1RI33yibibJkO9GjWQJY2eibCw4oFMeWM1yvUYCEiaQ\/132",
    "privilege": [],
    "unionid": "oSBoT6WGswnOunQ0XVx0"
}