[SOLVED] Masking access token by regex pattern match and replace in java

Masking access token by regex pattern match and replace in java

I'm trying to mask an access token with stars. The response payload is converted to a string. I need to match the token pattern with the string and replace the token value with stars.

{"accessToken":"knjnandHJHJBhjHJhjGhjghjGHJGhjgHJGjIG6gg8F68c6F6f6F6d67f79GV78INy8c5SV8n98f5D6g89Byf5446f678u8878GF756d57899bVY7TC6c7VY8UBi9u8","accessTokenExpirationTime":1800}

This should be like below

{"accessToken":"*********************************************************************************************************************","accessTokenExpirationTime":1800}

The code below cannot find a match and replace

String payload = PAYLOAD_STRING;
Pattern pattern = Pattern.compile("[a-zA-Z0-9]{126}$");
Matcher matcher = pattern.matcher(payload);
String result = matcher.replaceAll("<h1>*</h1>");
System.out.println(result);

Solution

You can use Pattern & Matcher like this:

String payload = ....;

Pattern pattern = Pattern.compile("\"accessToken\":\"([a-zA-Z0-9]+)\"");
Matcher matcher = pattern.matcher(payload);

if (matcher.find()) {
    String accessToken = matcher.group(1);
    String maskedToken = "*".repeat(accessToken.length());
    String result = payload.replace(accessToken, maskedToken);
    System.out.println(result);
} else {
    System.out.println("Access token not found.");
}