java1.8.java

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.Base64;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.stream.Collectors;

class Application {

    private static final String ENCODING = "UTF-8";

    public static void main(String[] args) throws java.lang.Exception {
        String url = "https://example.com/?vk_user_id=494075&vk_app_id=6736218&vk_is_app_user=1&vk_are_notifications_enabled=1&vk_language=ru&vk_access_token_settings=&vk_platform=android&sign=htQFduJpLxz7ribXRZpDFUH-XEUhC9rBPTJkjUFEkRA";
        String clientSecret = "wvl68m4dR1UpLrVRli";

        Map<String, String> queryParams = getQueryParams(new URL(url));

        String checkString = queryParams.entrySet().stream()
                .filter(entry -> entry.getKey().startsWith("vk_"))
                .sorted(Map.Entry.comparingByKey())
                .map(entry -> encode(entry.getKey()) + "=" + encode(entry.getValue()))
                .collect(Collectors.joining("&"));

        String sign = getHashCode(checkString, clientSecret);
        System.out.println(sign.equals(queryParams.getOrDefault("sign", "")) ? "ok" : "fail");
    }


    private static Map<String, String> getQueryParams(URL url) {
        final Map<String, String> result = new LinkedHashMap<>();
        final String[] pairs = url.getQuery().split("&");

        for (String pair : pairs) {
            int idx = pair.indexOf("=");
            String key = idx > 0 ? decode(pair.substring(0, idx)) : pair;
            String value = idx > 0 && pair.length() > idx + 1 ? decode(pair.substring(idx + 1)) : null;
            result.put(key, value);
        }

        return result;
    }

    private static String getHashCode(String data, String key) throws Exception {
        SecretKeySpec secretKey = new SecretKeySpec(key.getBytes(ENCODING), "HmacSHA256");
        Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(secretKey);
        byte[] hmacData = mac.doFinal(data.getBytes(ENCODING));
        return new String(Base64.getUrlEncoder().withoutPadding().encode(hmacData));
    }


    private static String decode(String value) {
        try {
            return URLDecoder.decode(value, ENCODING);
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        return value;
    }

    private static String encode(String value) {
        try {
            return URLEncoder.encode(value, ENCODING);
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        return value;
    }
}