Base64: java.lang.IllegalArgumentException: Illegal character

I'm trying to send a confirmation email after user registration. I'm using the JavaMail library for this purpose and the Java 8 Base64 util class.

I'm encoding user emails in the following way:

byte[] encodedEmail = Base64.getUrlEncoder().encode(user.getEmail().getBytes(StandardCharsets.UTF_8));
Multipart multipart = new MimeMultipart();
InternetHeaders headers = new InternetHeaders();
headers.addHeader("Content-type", "text/html; charset=UTF-8");
String confirmLink = "Complete your registration by clicking on following"+ "\n<a href='" + confirmationURL + encodedEmail + "'>link</a>";
MimeBodyPart link = new MimeBodyPart(headers,
confirmLink.getBytes("UTF-8"));
multipart.addBodyPart(link);

where confirmationURL is:

private final static String confirmationURL = "http://localhost:8080/project/controller?command=confirmRegistration&ID=";

And then decoding this in ConfirmRegistrationCommand in such way:

    String encryptedEmail = request.getParameter("ID");

    String decodedEmail = new String(Base64.getUrlDecoder().decode(encryptedEmail), StandardCharsets.UTF_8);

    RepositoryFactory repositoryFactory = RepositoryFactory
            .getFactoryByName(FactoryType.MYSQL_REPOSITORY_FACTORY);
    UserRepository userRepository = repositoryFactory.getUserRepository();
    User user = userRepository.find(decodedEmail);

    if (user.getEmail().equals(decodedEmail)) {
        user.setActiveStatus(true);
        return Path.WELCOME_PAGE;
    } else {
        return Path.ERROR_PAGE;
    }

And when I'm trying to decode:

http://localhost:8080/project/controller?command=confirmRegistration&ID=[B@6499375d

I'm getting java.lang.IllegalArgumentException: Illegal base64 character 5b.

I tried to use basic Encode/Decoder (not URL ones) with no success.

SOLVED:

The problem was the next - in the line:

 String confirmLink = "Complete your registration by clicking on following"+ "\n<a href='" + confirmationURL + encodedEmail + "'>link</a>";

I'm calling toString on an array of bytes, so I should do the following:

String encodedEmail = new String(Base64.getEncoder().encode(
                user.getEmail().getBytes(StandardCharsets.UTF_8)));

Thanks to Jon Skeet and ByteHamster.

Your encoded text is [B@6499375d. That is not Base64, something went wrong while encoding. That decoding code looks good.

Use this code to convert the byte[] to a String before adding it to the URL:

String encodedEmailString = new String(encodedEmail, "UTF-8");
// ...
String confirmLink = "Complete your registration by clicking on following"
    + "\n<a href='" + confirmationURL + encodedEmailString + "'>link</a>";