Sample of Java Pattern -- Template Method

EmailTemplate.java

package templatemethod;

import javax.mail.*;
import javax.mail.internet.*;

public abstract class EmailTemplate {
    public void send(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd, String[] recipients, String subject,String message, String from){
        MimeMessage msg = connect(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd);
        try {
            InternetAddress addressFrom = new InternetAddress(from);
            msg.setFrom(addressFrom);

            InternetAddress[] addressTo = new InternetAddress[recipients.length];
            for (int i = 0; i < recipients.length; i++) {
                addressTo[i] = new InternetAddress(recipients[i]);
            }
            msg.setRecipients(Message.RecipientType.TO, addressTo);

            msg.setSubject(subject);
            msg.setContent(message, "text/html");
            Transport.send(msg);
        } catch (MessagingException e) {
            System.out.println("Could not send this email, title=" + subject + " addressTo=" + recipients[0] + ", please check the email server connection.");
        }
    }
    
    protected abstract MimeMessage connect(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd);
}

GeneralEmailService.java

package templatemethod;

import java.security.Security;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Session;
import javax.mail.internet.MimeMessage;

import templatemethod.GoogleEmailService.SMTPAuthenticator;

public class GeneralEmailService extends EmailTemplate{
    private String smtpAuthUser;
    private String smtpAuthPwd;
    protected MimeMessage connect(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd){
        
        this.smtpAuthUser = smtpAuthUser;
        this.smtpAuthPwd = smtpAuthPwd;
        
        boolean debug = false;

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", smtpHostName);
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", smtpPort);
        props.setProperty("mail.smtp.quitwait", "false");

        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);

        session.setDebug(debug);

        MimeMessage msg = new MimeMessage(session);
        
        return msg;
        
    }
    
    private class SMTPAuthenticator extends javax.mail.Authenticator {
        public PasswordAuthentication getPasswordAuthentication() {
            String username = smtpAuthUser;
            String password = smtpAuthPwd;
            return new PasswordAuthentication(username, password);
        }
    }


}

GoogleEmailService.java

package templatemethod;

import java.security.Security;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.internet.MimeMessage;

public class GoogleEmailService extends EmailTemplate{
    private String smtpAuthUser;
    private String smtpAuthPwd;
    protected MimeMessage connect(String smtpHostName, String smtpPort, String smtpAuthUser, String smtpAuthPwd){
        
        this.smtpAuthUser = smtpAuthUser;
        this.smtpAuthPwd = smtpAuthPwd;
        
        boolean debug = false;

        Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", smtpHostName);
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", smtpPort);
        props.setProperty("mail.smtp.quitwait", "false");

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

        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);

        session.setDebug(debug);

        MimeMessage msg = new MimeMessage(session);
        
        return msg;
        
    }
    
    private class SMTPAuthenticator extends javax.mail.Authenticator {
        public PasswordAuthentication getPasswordAuthentication() {
            String username = smtpAuthUser;
            String password = smtpAuthPwd;
            return new PasswordAuthentication(username, password);
        }
    }

}

TemplateMethodTest.java

package templatemethod;

public class TemplateMethodTest {

    public static void main(String[] args) {
        String smtpHostName = "";
        String smtpPort = "";
        String smtpAuthUser = "";
        String smtpAuthPwd = "";
        String[] recipients = {""};
        String subject = "";
        String message = "";
        String from = "";
        EmailTemplate googleEmailService = new GoogleEmailService();
        googleEmailService.send(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd, recipients, subject, message, from);
        EmailTemplate generalEmailService = new GeneralEmailService();
        generalEmailService.send(smtpHostName, smtpPort, smtpAuthUser, smtpAuthPwd, recipients, subject, message, from);
    }

}

you may download the source code.