获取微信身份令牌

    // 开发者ID
    private static final String APPID = "";
    // 开发者密码
    private static final String SECRET = "";
    // 授权码发放类型
    private static final String GRANT_TYPE = "client_credential";
    // 授权码类型
    private static final String TYPE = "jsapi";
    // 获取微信 TOKEN 接口
    private static final String ACCESS_TOKEN_URL = "https://api.weixin.qq.com/cgi-bin/token";
    // 获取微信令牌接口
    private static final String TICKET_URL = "https://api.weixin.qq.com/cgi-bin/ticket/getticket";

    // 请求参数名
    private static final String ACCESS_TOKEN_KEY = "access_token";
    private static final String TICKET_KEY = "ticket";

    // JSON 解析
    private static JsonParser parse = new JsonParser();

    // 注意 URL 一定要动态获取，不能 hardcode
    public static Map weChatSignature(String url) {
        String token = getToken();
        Map result = new HashMap();

        String ticket = getTicket(token);
        String nonceStr = UUID.randomUUID().toString();                      // 随机字符串
        String timestamp = Long.toString(System.currentTimeMillis() / 1000); // 时间戳
        
        //注意这里参数名必须全部小写，且必须有序
        String context = "jsapi_ticket=" + ticket + "&noncestr=" + nonceStr + 
                         "×tamp=" + timestamp + "&url=" + url;
        String signature = SHA1(context);

        result.put("url", url);
        result.put("jsapi_ticket", ticket);
        result.put("nonce_str", nonceStr);
        result.put("timestamp", timestamp);
        result.put("signature", signature);
        result.put("appid", APPID);

        return result;
    }

    // 获取 token
    public static String getToken() {
        // https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=&secret=
        String url = ACCESS_TOKEN_URL + "?grant_type=" + GRANT_TYPE + "&appid=" + APPID + "&secret=" + SECRET;
        String response = httpGetForJson(url);
        return ((JsonObject) parse.parse(response)).get(ACCESS_TOKEN_KEY).getAsString();
    }

    // 获取 ticket
    public static String getTicket(String token) {
        // https://api.weixin.qq.com/cgi-bin/ticket/getticket?access_token=&type=
        String url = TICKET_URL + "?access_token=" + token + "&type=" + TYPE;
        String response = httpGetForJson(url);
        return ((JsonObject) parse.parse(response)).get(TICKET_KEY).getAsString();
    }

    // 发送请求
    public static String httpGetForJson(String url) {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            // 创建 HTTPGET
            HttpGet httpget = new HttpGet(url);
            // 发送 GET 请求
            CloseableHttpResponse response = httpclient.execute(httpget);
            HttpEntity entity = response.getEntity();
            return entity == null ? "" : EntityUtils.toString(entity);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return "";
    }

    // 加密
    public static String SHA1(final String value) {
        MessageDigest digest;
        try {
            digest = MessageDigest.getInstance("SHA-1");
            digest.update(value.getBytes());
            byte messageDigest[] = digest.digest();
            StringBuffer hexString = new StringBuffer();
            for (int i = 0; i < messageDigest.length; i++) {
                String shaHex = Integer.toHexString(messageDigest[i] & 0xFF);
                if (shaHex.length() < 2) {
                    hexString.append(0);
                }
                hexString.append(shaHex);
            }
            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return "";
    }