send email using Java

It is said that we could conveniently sending email in Java. with the requirement of my project, I started to use it for my solution.

package requirement

sending email in Java needs two part of jar, First of it is the JavaEE declared API which do not includes implementation. Another part is provided by vendor, different web server may have disparate support.
For me, com.sun.mail has rather enough function.
In maven you need to add two <dependency>

<dependency>
    <groupId>com.sun.mail</groupId>
    <artifactId>javax.mail</artifactId>
    <version>1.5.1</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.1</version>
</dependency>

Please refer to JavaMail API for further exploration.

coding

I want to implement the mailing function in a clear way, hence I separate it into three parts by sender-info mail-info and mail-sending.
First part includes information about the sender, the procedure of sending email regularly needs a logined session from sender, which is similar to the procedure of logining mail.google.com by your gmail account.
So you need to fill the account authentication in this class:

package rugal.mail.pojo;

/**
 *
 * @author Rugal Bernstein
 */
public class Sender
{

    private final String emailAddress;

    private String password;

    //simply resolve smtp host name by default, could manually change later
    private String smtpHostName;

    //default smtp port is 25, but some mail system will have different port
    private String smtpPort = "25";

    public String getEmailAddress()
    {
        return emailAddress;
    }

    public String getUsername()
    {
        return emailAddress.split("@")[0];
    }

    public String getPassword()
    {
        return password;
    }

    public void setPassword(String password)
    {
        this.password = password;
    }

    public String getSmtpHostName()
    {
        return smtpHostName;
    }

    public void setSmtpHostName(String smtpHostName)
    {
        this.smtpHostName = smtpHostName;
    }

    public String getSmtpPort()
    {
        return smtpPort;
    }

    public void setSmtpPort(String smtpPort)
    {
        this.smtpPort = smtpPort;
    }

    public Sender(String emailAddress)
    {
        this.emailAddress = emailAddress;
        resolveSmtpHost();
    }

    private void resolveSmtpHost()
    {
        this.smtpHostName = "smtp." + this.emailAddress.split("@")[1];
    }
}

I think there is a very strange design in javax.mail, it needs to inherit Authenticator class to provide identity autorization, as below.
I still could not figure out the reason, since this could be better designed.

package rugal.mail.pojo;

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;

/**
 *
 * @author Rugal Bernstein
 */
public class AccountAuthenticator extends Authenticator
{

    private String id = null;

    private String password = null;

    public AccountAuthenticator(String id, String password)
    {
        this.id = id;
        this.password = password;
    }

    @Override
    protected PasswordAuthentication getPasswordAuthentication()
    {
        return new PasswordAuthentication(id, password);
    }
}

And this is my mail information class that includes the recipient address and mail content.
It will be very conveinent!

package rugal.mail.pojo;

/**
 *
 * @author Rugal Bernstein
 */
public class Mail
{

    private final String recipient;

    private String subject;

    public String getRecipient()
    {
        return recipient;
    }

    private String content = "";

    public String getSubject()
    {
        return subject;
    }

    public void setSubject(String subject)
    {
        this.subject = subject;
    }

    public String getContent()
    {
        return content;
    }

    public void setContent(String content)
    {
        this.content = content;
    }

    public Mail(String recipient)
    {
        this.recipient = recipient;
    }

    public Mail(String recipient, String subject, String content)
    {
        this.recipient = recipient;
        this.subject = subject;
        this.content = content;
    }

}

And this is a service class that provide integrated function of sending mail.

package rugal.mail.service;

import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import org.springframework.stereotype.Service;
import rugal.mail.pojo.AccountAuthenticator;
import rugal.mail.pojo.Mail;
import rugal.mail.pojo.Sender;

/**
 * This is a mail service provide mail sending function<BR/>
 * This class is designed as one to many mailing method<BR/>
 * you need to provide sender instance as constructor parameter<BR/>
 * then use <code>send</code> method to send mail
 *
 * @author Rugal Bernstein
 */
@Service
public class SendMailService
{

    private static final String mail_smtp_auth = "mail.smtp.auth";

    private static final String mail_smtp_starttls_enable = "mail.smtp.starttls.enable";

    private static final String mail_smtp_host = "mail.smtp.host";

    private static final String mail_smtp_port = "mail.smtp.port";

    private Session session;

    private final Sender sender;

    private final Properties properties = new Properties();

    public SendMailService(Sender sender)
    {
        this.sender = sender;
        properties.put(mail_smtp_starttls_enable, "true");
        properties.put(mail_smtp_auth, "true");
        properties.put(mail_smtp_host, sender.getSmtpHostName());
        properties.put(mail_smtp_port, sender.getSmtpPort());

    }

    public void send(Mail mail) throws MessagingException
    {
        if (null == session) {
            //need this authenticator class to specify authentication
            session = Session.getDefaultInstance(properties, 
                   new AccountAuthenticator(sender.getUsername(), sender.getPassword()));
        }
        MimeMessage message = new MimeMessage(session);
        message.setFrom(new InternetAddress(sender.getEmailAddress()));
        InternetAddress toAddress = new InternetAddress(mail.getRecipient());

        message.addRecipient(Message.RecipientType.TO, toAddress);

        message.setSubject(mail.getSubject());
        message.setText(mail.getContent());
        Transport.send(message);
    }
}

test functionality

I like to use JUnit to do the unit test.

package rugal.mail.service;

import javax.mail.MessagingException;
import org.junit.Before;
import org.junit.Test;
import rugal.mail.pojo.Mail;
import rugal.mail.pojo.Sender;

/**
 *
 * @author Rugal Bernstein
 */
public class SendMailServiceTest
{

    private Mail mail;

    private Sender sender;

    private SendMailService instance;

    @Before
    public void setUp()
    {
        mail = new Mail("example@web.com");
        mail.setContent("This is a test mail");
        mail.setSubject("This is a test subject");
        sender = new Sender("example@web.com");
        sender.setPassword("123456");
        instance = new SendMailService(sender);

    }

    /**
     * Test of send method, of class MailSender.
     *
     * @throws javax.mail.MessagingException
     */
    @Test
    public void testSend() throws MessagingException
    {
        System.out.println("begin");
        instance.send(mail);
        System.out.println("end");
    }
}

Seems everything is done!
JavaMail API is pulchritude indeed!