Segurança

package com.transfersmile.ts;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import java.util.Map;
import java.util.TreeMap;

public static String getSign(Map<String, String> params, String authKey) {
    String param = sortParam(params) + authKey;
    return sha256(param);
}

public static String sha256(String str) {
    String encodeStr = "";
    try {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        byte[] encodedhash = digest.digest(str.getBytes(StandardCharsets.UTF_8));
        encodeStr = bytesToHex(encodedhash);
    } catch (NoSuchAlgorithmException e) {
        throw new RuntimeException("algorithm not supported");
    }
    return encodeStr;
}

public static String sortParam(Map<String, String> params) {
    try {
        Map<String, String> map = new TreeMap<>(params);

        StringBuilder sb = new StringBuilder();
        for (String k : map.keySet()) {
            String v = map.get(k);
            if (v != null && v.length() > 0) {
                sb.append(k).append("=").append(v).append("&");
            }
        }

        if (sb.length() <= 0) {
            return "";
        }

        return sb.subSequence(0, sb.length() - 1).toString();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return "";
}

private static String bytesToHex(byte[] hash) {
    StringBuilder hexString = new StringBuilder(2 * hash.length);
    for (int i = 0; i < hash.length; i++) {
        String hex = Integer.toHexString(0xff & hash[i]);
        if (hex.length() == 1) {
            hexString.append('0');
        }
        hexString.append(hex);
    }
    return hexString.toString();
}