JavaMail: Sending an email message to an SMTP server which uses authentication

JavaMail_SMTP_with_authentication.java

import java.util.Properties;
import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMessage.RecipientType;

public class SMTPAuthEmail {
	private Session session;
	
	public static void main(String[] args) throws MessagingException {
		new SMTPAuthEmail().send();
	}
	
	public SMTPAuthEmail() {
		Authenticator authenticator = new Authenticator() {
			private PasswordAuthentication authentication;
			
			{
				authentication = new PasswordAuthentication("username", "password");
			}
			
			protected PasswordAuthentication getPasswordAuthentication() {
				return authentication;
			}
		};
		
		Properties props = new Properties();
		props.put("mail.transport.protocol", "smtp");
		props.put("mail.smtp.host", "smtp.somewhere.com");
		props.put("mail.smtp.port", "587");
		props.put("mail.smtp.auth", "true");
		
		session = Session.getDefaultInstance(props, authenticator);
	}
	
	private void send() throws MessagingException {
		Message message = new MimeMessage(session);
		
		message.setFrom(new InternetAddress("[email protected]"));
		message.addRecipient(RecipientType.TO, new InternetAddress("[email protected]"));
		
		message.setSubject("Hello world!");
		message.setContent("Sent via an SMTP server with authentication.", "text/plain");
		
		Transport.send(message);
	}
}

Part_1-Authenticator.java

Authenticator authenticator = new Authenticator() {
	private PasswordAuthentication authentication;

	{
		authentication = new PasswordAuthentication("username", "password");
	}

	protected PasswordAuthentication getPasswordAuthentication() {
		return authentication;
	}
};

Part_2-Properties_and_Session.java

Properties props = new Properties();
props.put("mail.transport.protocol", "smtp");
props.put("mail.smtp.host", "smtp.somewhere.com");
props.put("mail.smtp.port", "587");
props.put("mail.smtp.auth", "true");
		
Session session = Session.getDefaultInstance(props, authenticator);

Part_3-Sending.java

Message message = new MimeMessage(session);

message.setFrom(new InternetAddress("[email protected]"));
message.addRecipient(RecipientType.TO, new InternetAddress("[email protected]"));

message.setSubject("Hello world!");
message.setContent("Sent via an SMTP server with authentication.", "text/plain");

Transport.send(message);