Decode base64Url in Java

Question

https://web.archive.org/web/20110422225659/https://en.wikipedia.org/wiki/Base64#URL_applications

talks about base64Url - Decode

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a modified Base64 for URL variant exists, where no padding '=' will be used, and the '+' and '/' characters of standard Base64 are respectively replaced by '-' and '_'

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I created the following function:

public static String base64UrlDecode(String input) {
    String result = null;
    BASE64Decoder decoder = new BASE64Decoder();
    try {
        result = decoder.decodeBuffer(input.replace('-','+').replace('/','_')).toString();
    }
    catch (IOException e) {
        System.out.println(e.getMessage());
    }
    return result;
}

it returns a very small set of characters that don't even resemble to the expected results. any ideas?

Answer 1

With the usage of Base64 from Apache Commons, who can be configured to URL safe, I created the following function:

import org.apache.commons.codec.binary.Base64;

public static String base64UrlDecode(String input) {
    String result = null;
    Base64 decoder = new Base64(true);
    byte[] decodedBytes = decoder.decode(input);
    result = new String(decodedBytes);
    return result;
}

The constructor Base64(true) makes the decoding URL-safe.