AuthenticationFailedException using Gmail in Javax

I’m developing a method to send emails, but Gmail doesn’t work. I’m reciving:

javax.mail.AuthenticationFailedException: 535-5.7.8 Username and Password not accepted.

The idea of the code is to send a simple message:

class SimpleAuth extends Authenticator {
    public String username = null;
    public String password = null;

    public SimpleAuth(String user, String pwd) {
        username = user;
        password = pwd;
    }

    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(username, password);
    }
}

public boolean send() throws Exception {
    // Smtp server
    final String smtp = "smtp.gmail.com";
    final String port = "465";

    // Properties setting
    Properties props = new Properties();

    props.setProperty("mail.host", "cServSmtp");
    props.put("mail.transport.protocol", "smtp");

    props.put("mail.smtp.host", smtp);
    props.put("mail.smtp.auth", "true");

    props.put("mail.smtp.user", username);
    props.put("mail.debug", "true");
    props.put("mail.smtp.port", port);
    props.put("mail.smtp.socketFactory.port", port);

    props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");

    props.put("mail.smtp.socketFactory.fallback", "true");

    props.put("mail.smtp.ssl.protocols", "TLSv1.2");

    props.put("mail.smtp.starttls.enable", "true");

    // Authentication
    SimpleAuth auth = new SimpleAuth(username, password);

    // Instance session
    Session session = Session.getInstance(props, auth);
    session.setDebug(false);

    // Message setting
    Message msg = new MimeMessage(session);
    msg.setRecipient(Message.RecipientType.TO, new InternetAddress(recipientEmail));

    msg.setFrom(new InternetAddress(username, "Diego Borba"));
    msg.setSubject("Subject");
    msg.setContent("Text here", "text/plain");

    // Instance transport
    Transport tr = session.getTransport();

    try {
        // Send e-mail
        tr = session.getTransport("smtp");
        tr.connect(smtp, username, password);
        msg.saveChanges();
        tr.sendMessage(msg, msg.getAllRecipients());
        tr.close();
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
    return true;
}

I changed a bit of the code to facilitate reproduction, but the idea is the same.

Important observations:

• It worked with Outlook and Hotmail (smtp.office365.com)
• I made sure the username and password are correct.
• I must use SSL.
• I checked Google Support, but I didn’t find anything.
• I’m using Java8 (Jre 1.8.0_361)

>Solution :

This happends becouse you dont alowed the Less Secure Apps in your Google account.

You just need to change this configuration!

Check this out: Solve error javax.mail.AuthenticationFailedException