java实现微信扫码登录第三方网站功能（原理和代码）

示例：　　
{　　　　
    "access_token":"ACCESS_TOKEN",
    "expires_in":7200,　　　　
    "refresh_token":"REFRESH_TOKEN",　　　　
    "openid":"OPENID",　　　　
    "scope":"SCOPE"　　
}

示例；
{　 
    "openid":"OPENID",
　　"nickname":"NICKNAME",
　　"sex":1,
　　"province":"PROVINCE",
　　"city":"CITY",
　　"country":"COUNTRY",
　　"headimgurl": "http://wx.qlogo.cn/mmopen/g3MonUZtNHkdmzicIlibx6iaFqAc56vxLSUfpb6n5WKSYVY0ChQKkiaJSgQ1dZuTOgvLLrhJbERQQ4eMsv84eavHiaiceqxibJxCfHe/0",
　　"privilege":["PRIVILEGE1","PRIVILEGE2"],
　　"unionid": " o6_bmasdasdsad6_2sgVt7hMZOPfL"
}

public class Token {
    private String openid; //授权用户唯一标识
    private String accessToken; //接口调用凭证
    private Integer ExpiresIn; //access_token接口调用凭证超时时间，单位（秒）
    public String getOpenid() {
        return openid;
    }
    public void setOpenid(String openid) {
        this.openid = openid;
    }
    public String getAccessToken() {
        return accessToken;
    }
    public void setAccessToken(String accessToken) {
        this.accessToken = accessToken;
    }
    public Integer getExpiresIn() {
        return ExpiresIn;
    }
    public void setExpiresIn(Integer expiresIn) {
        ExpiresIn = expiresIn;
    }

public class WechatUserInfo {
    private String unionid;  //用户唯一标识
    private String nickname; //昵称
    private String headimgurl; //头像地址
    private String subscribe; // 用户是否订阅该公众号标识，值为0时，代表此用户没有关注该公众号，拉取不到其余信息。 1 用户已经绑定公众号
    public String getUnionid() {
        return unionid;
    }
    public void setUnionid(String unionid) {
        this.unionid = unionid;
    }
    public String getNickname() {
        return nickname;
    }
    public void setNickname(String nickname) {
        this.nickname = nickname;
    }
    public String getHeadimgurl() {
        return headimgurl;
    }
    public void setHeadimgurl(String headimgurl) {
        this.headimgurl = headimgurl;
    }
    public String getSubscribe() {
        return subscribe;
    }
    public void setSubscribe(String subscribe) {
        this.subscribe = subscribe;
    }

public static String urlEncodeUTF8(String source){
    String result = source;
    try {
        result = java.net.URLEncoder.encode(source,"utf-8");
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
    return result;
}

/**
* 发送https请求
* @param requestUrl 请求地址
* @param requestMethod 请求方式（GET、POST）
* @param outputStr 提交的数据
* @return 返回微信服务器响应的信息
*/

public static String httpsRequest(String requestUrl, String requestMethod, String outputStr) {
        try {
            // 创建SSLContext对象，并使用我们指定的信任管理器初始化
            TrustManager[] tm = { new MyX509TrustManager() };
            SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE");
            sslContext.init(null, tm, new java.security.SecureRandom());
            // 从上述SSLContext对象中得到SSLSocketFactory对象
            SSLSocketFactory ssf = sslContext.getSocketFactory();
            URL url = new URL(requestUrl);
            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            conn.setSSLSocketFactory(ssf);
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setUseCaches(false);
            // 设置请求方式（GET/POST）
            conn.setRequestMethod(requestMethod);
            conn.setRequestProperty("content-type", "application/x-www-form-urlencoded"); 
            // 当outputStr不为null时向输出流写数据
            if (null != outputStr) {
                OutputStream outputStream = conn.getOutputStream();
                // 注意编码格式
                outputStream.write(outputStr.getBytes("UTF-8"));
                outputStream.close();
            }
            // 从输入流读取返回内容
            InputStream inputStream = conn.getInputStream();
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "utf-8");
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String str = null;
            StringBuffer buffer = new StringBuffer();
            while ((str = bufferedReader.readLine()) != null) {
                buffer.append(str);
            }
            // 释放资源
            bufferedReader.close();
            inputStreamReader.close();
            inputStream.close();
            inputStream = null;
            conn.disconnect();
            return buffer.toString();
        } catch (ConnectException ce) {
            log.error("连接超时：{}", ce);
        } catch (Exception e) {
            log.error("https请求异常：{}", e);
        }
        return null;
    }
    

public static Token getTokenWithOpenid(String appid, String appsecret, String code) {
        String findAccessTokenUrl = "https://api.weixin.qq.com/sns/oauth2/access_token?appid=APPID&secret=SECRET&code=CODE&grant_type=authorization_code";
        Token token = null;
        String requestUrl = findAccessTokenUrl.replace("APPID", appid).replace("SECRET", appsecret).replace("CODE", code);// 发起GET请求获取凭证
        JSONObject jsonObject = JSONObject.fromObject(httpsRequest(requestUrl, "GET", null));

        if (null != jsonObject) {
            try {
                token = new Token();
                token.setOpenid(jsonObject.getString("openid"));
                token.setAccessToken(jsonObject.getString("access_token"));
                token.setExpiresIn(jsonObject.getInt("expires_in"));
            } catch (JSONException e) {
                token = null;
                // 获取token失败
                log.error("获取token失败 errcode:{} errmsg:{}", jsonObject.getInt("errcode"), jsonObject.getString("errmsg"));
            }
        }
        return token;
    }

public static WechatUserInfo  getUserinfo(String access_token, String openid) {
        WechatUserInfo wxuse = new WechatUserInfo();
        String findUseinfo = "https://api.weixin.qq.com/sns/userinfo?access_token=ACCESS_TOKEN&openid=OPENID";
        String requestUrl = findUseinfo.replace("ACCESS_TOKEN", access_token).replace("OPENID", openid);
        JSONObject jsonObject = JSONObject.fromObject(httpsRequest(requestUrl, "GET", null));

        if (null != jsonObject) {
            try {
                wxuse.setNickname(jsonObject.getString("nickname"));
                wxuse.setHeadimgurl(jsonObject.getString("headimgurl"));
                wxuse.setUnionid(jsonObject.getString("unionid"));
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        return wxuse;
    }

public String weChatLanded(){
        String requestUrl  = "https://open.weixin.qq.com/connect/qrconnect?appid=APPID&redirect_uri=REDIRECT_URI&response_type=code&scope=SCOPE&state=STATE#wechat_redirect";
        String loginAppid = "wxea43f181e32e8df0";  //微信申请的appid
        String loginRedirectUrl = "https://www.jb51.net/weChatLogin_epf.action";//调用微信接口后返回的资源名
        String loginScope = "snsapi_login";//写死
        redirectURL = requestUrl.replace("APPID", loginAppid).replace("REDIRECT_URI", CommonUtil.urlEncodeUTF8(loginRedirectUrl)).replace("SCOPE", loginScope);
        return SUCCESS;
    }

@SuppressWarnings("static-access")
        public String weChatLogin_epf(){
            //通过code获取access_token
            String loginAppid = "wxea43f181e32e8df0";
            String loginSecrect = "4721e5f744e6c0f3c4094b25449ee7e3";
            Token tokenWithOpenid = CommonUtil.getTokenWithOpenid(loginAppid, loginSecrect,code);
            String openid = tokenWithOpenid.getOpenid();
            String access_token = tokenWithOpenid.getAccessToken();
            //通过access_token调用接口
            WechatUserInfo wxuse  = CommonUtil.getUserinfo(access_token, openid);
            return SUCCESS;
        }