APP URL签名验证的实现API防篡改

/**
 * 签名生成算法
 * @param HashMap<String,String> params 请求参数集，所有参数必须已转换为字符串类型
 * @param String secret 签名密钥
 * @return 签名
 * @throws IOException
 */
public static String getSignature(HashMap<String,String> params, String secret) throws IOException
{
    // 先将参数以其参数名的字典序升序进行排序
    Map<String, String> sortedParams = new TreeMap<String, String>(params);
    Set<Entry<String, String>> entrys = sortedParams.entrySet();
    // 遍历排序后的字典，将所有参数按"key=value"格式拼接在一起
    StringBuilder basestring = new StringBuilder();
    for (Entry<String, String> param : entrys) {
        basestring.append(param.getKey()).append("=").append(param.getValue());
    }
    basestring.append(secret);
    // 使用MD5对待签名串求签
    byte[] bytes = null;
    try {
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        bytes = md5.digest(basestring.toString().getBytes("UTF-8"));
    } catch (GeneralSecurityException ex) {
        throw new IOException(ex);
    }
    // 将MD5输出的二进制结果转换为小写的十六进制
    StringBuilder sign = new StringBuilder();
    for (int i = 0; i < bytes.length; i++) {
        String hex = Integer.toHexString(bytes[i] & 0xFF);
        if (hex.length() == 1) {
            sign.append("0");
        }
        sign.append(hex);
    }
    return sign.toString();
}