HMAC in Java

hmac.java

package hello;

import javax.crypto.Mac;
import javax.crypto.spec.*;

public class HMAC {
    public void hash() {
        try {
            String secret = "salt";// 加密使用的key
            String message = "1";// 需要加密的字符串（本项目是 "{uuid}_{timestamp}" ）

            Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
            SecretKeySpec secret_key = new SecretKeySpec(secret.getBytes(), "HmacSHA256");
            sha256_HMAC.init(secret_key);

            String hash = byteArrayToHexString(sha256_HMAC.doFinal(message.getBytes()));// 重点
            System.out.println(hash);
        }
        catch (Exception e){
            System.out.println("Error");
        }
    }

    @org.jetbrains.annotations.NotNull
    private static String byteArrayToHexString(byte[] b) {
        StringBuilder hs = new StringBuilder();
        String stmp;
        for (int n = 0; b!=null && n < b.length; n++) {
            stmp = Integer.toHexString(b[n] & 0XFF);
            if (stmp.length() == 1)
                hs.append('0');
            hs.append(stmp);
        }
        return hs.toString().toLowerCase();
    }
}