Validate Alma webhook signature in Java

ValidateSignature.java

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Base64;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public class ValidateSignature {

  public static String encode(String key, byte[] data) throws Exception {
    Mac hmac = Mac.getInstance("HmacSHA256");
    SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), key);
    hmac.init(secret_key);
    return Base64.getEncoder().encodeToString(hmac.doFinal(data));
  }

  public static void main(String [] args) throws Exception {
    System.out.println(encode(args[0], Files.readAllBytes(Paths.get(args[1]))));
  }
}

$ javac ValidateSignature.java
$ java ValidateSignature [KEY] ../json.txt
I/OLK158f+VJrF0cy8bNszVo6rcwl6/97p6Xqm9cqMM=