List files in a folder inside classpath

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final var dir = "/com/";

final var uri = getClass().getResource(dir).toURI();
System.out.println("uri = " + uri);

final var pathInCP = "jar".equals(uri.getScheme()) ?
  FileSystems.newFileSystem(uri, Collections.emptyMap()).getPath(dir) :
  Paths.get(uri);

Files.list(pathInCP).forEach(path -> {
  final var fileName = path.getFileName().toString();
  final var type = Files.isRegularFile(path) ? "file" : Files.isDirectory(path) ? "dir" : "?";
  System.out.println("File: '" + fileName + "' - type: " + type);
});

ExecutorService & invokeAll()

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final var callables = IntStream
  .range(1, 5)
  .mapToObj(operand -> (Callable<Integer>) () -> {
      Thread.sleep(operand * 1000);
      System.out.printf("callable[%s]: operand=%s\n", Thread.currentThread().getName(), operand);
      return operand;
  })
  .collect(Collectors.toList());

final var service = Executors.newFixedThreadPool(callables.size());
final var futures = service.invokeAll(callables, 3, TimeUnit.SECONDS);
service.shutdown();

System.out.printf("\nfutures.size() = %s\n\n", futures.size());
for (int i = 0; i < futures.size(); i++) {
  final var future = futures.get(i);
  if (future.isCancelled()) {
    System.err.printf("%s: canceled\n", i + 1);
  } else {
    final Integer rs = future.get();
    System.out.printf("%s: result = %s\n", i + 1, rs);
  }
}

Output is:

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callable[pool-1-thread-1]: operand=1
callable[pool-1-thread-2]: operand=2

futures.size() = 4

1: result = 1
2: result = 2
3: canceled
4: canceled

Replace text by Pattern

Suppose in a payment system, we have some nested JSONs with its signatures. We want to log received messages, however the security team has forced you to mask following fields before writing to log files: srcCardId, destCardId, trx, and refNo.

Following code is just a simulation for single message, and you want to log received serverSignedJson.

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final var mapper = new ObjectMapper();

final var trxUser = new TransferUserData("c123-1-9870", "c345-1-9871", 1210L, 23874623L, 1000001L, null);
final var trxUserJson = mapper.writeValueAsString(trxUser);
System.out.println("trxUser = " + trxUserJson);

final var userSigned = new SignedData(trxUserJson, signByUser(trxUserJson));
final var userSignedJson = mapper.writeValueAsString(userSigned);
System.out.println("userSigned = " + userSignedJson);

final var serverData = new ServerData("1000", userSignedJson);
final var serverDataJson = mapper.writeValueAsString(serverData);
System.out.println("serverData = " + serverDataJson);

final var serverSigned = new SignedData(serverDataJson, signByServer(serverDataJson));
final var serverSignedJson = mapper.writeValueAsString(serverSigned);
System.out.println("serverSigned = " + serverSignedJson);

The output is something like this:

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trxUser = {"srcCardId":"c123-1-9870","destCardId":"c345-1-9871","amount":1210,"trxId":23874623,"refNo":1000001,"trx":null}
userSigned = {"raw":"{\"srcCardId\":\"c123-1-9870\",\"destCardId\":\"c345-1-9871\",\"amount\":1210,\"trxId\":23874623,\"refNo\":1000001,\"trx\":null}","signed":"SIGNED_BY_USER"}
serverData = {"serverId":"1000","signedUserData":"{\"raw\":\"{\\\"srcCardId\\\":\\\"c123-1-9870\\\",\\\"destCardId\\\":\\\"c345-1-9871\\\",\\\"amount\\\":1210,\\\"trxId\\\":23874623,\\\"refNo\\\":1000001,\\\"trx\\\":null}\",\"signed\":\"SIGNED_BY_USER\"}"}
serverSigned = {"raw":"{\"serverId\":\"1000\",\"signedUserData\":\"{\\\"raw\\\":\\\"{\\\\\\\"srcCardId\\\\\\\":\\\\\\\"c123-1-9870\\\\\\\",\\\\\\\"destCardId\\\\\\\":\\\\\\\"c345-1-9871\\\\\\\",\\\\\\\"amount\\\\\\\":1210,\\\\\\\"trxId\\\\\\\":23874623,\\\\\\\"refNo\\\\\\\":1000001,\\\\\\\"trx\\\\\\\":null}\\\",\\\"signed\\\":\\\"SIGNED_BY_USER\\\"}\"}","signed":"SIGNED_BY_SERVER"}

The mask() method tries to find the fields’ value and replace it via using regex:

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String mask(String json) {
  final var pattern = Pattern.compile(
	  "\"(srcCardId|destCardId|trx|refNo)\\\\*?\":.*?(null|\"(?<STRVAL>.*?)\\\\*?\"|(?<NUMVAL>\\d+))");

  final Matcher matcher = pattern.matcher(json);

  final StringBuilder builder = new StringBuilder();

  while (matcher.find()) {
    final String expr = matcher.group(0);

    if (matcher.group("STRVAL") != null || matcher.group("NUMVAL") != null) {

      final String replacement = matcher.group("STRVAL") != null ?
        matcher.group("STRVAL") :
        matcher.group("NUMVAL");

      final String newStr = replacement.length() > 2 ?
        "*".repeat(replacement.length() - 2) + replacement.substring(replacement.length() - 2) :
        replacement;

      final String newExpr = expr.replace(replacement, newStr);
      matcher.appendReplacement(builder, Matcher.quoteReplacement(newExpr));
    } else {
      matcher.appendReplacement(builder, Matcher.quoteReplacement(expr));
    }
  }
  matcher.appendTail(builder);
  return builder.toString();
}

The output is this:

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serverSignedJson = {"raw":"{\"serverId\":\"1000\",\"signedUserData\":\"{\\\"raw\\\":\\\"{\\\\\\\"srcCardId\\\\\\\":\\\\\\\"*********70\\\\\\\",\\\\\\\"destCardId\\\\\\\":\\\\\\\"*********71\\\\\\\",\\\\\\\"amount\\\\\\\":1210,\\\\\\\"trxId\\\\\\\":23874623,\\\\\\\"refNo\\\\\\\":*****01,\\\\\\\"trx\\\\\\\":null}\\\",\\\"signed\\\":\\\"SIGNED_BY_USER\\\"}\"}","signed":"SIGNED_BY_SERVER"}