Java Mail API: Getting Started

Now we will see how to put it all together as a class that can be extended and reused. So let's get started.

Start with the package name.

package ap.mail;

Then come the imports.

The last two imports are important if the password authenticator has to be used.

Next is the class. The class must subclass the Authenticator, as the class itself would implement the logic for password authentication.

The variables to be used across the methods have to be declared.

public class MailClient extends Authenticator
{
  protected String from;
  protected Session session;
  protected PasswordAuthentication authentication;
  protected Folder rootFolder,currentFolder;
  protected Store store;
  :
}

Then comes the constructor. Since the Properties will be used to pass the information regarding the host username and password, the object of the Properties class would be instantiated here.

public class MailClient extends Authenticator
{
 protected String from;
  protected Session session;
  protected PasswordAuthentication authentication;
  protected Folder rootFolder,currentFolder;
  protected Store store;

  public MailClient(String user, String host, boolean debug,String password)
  {
    from = user + '@' + host;
    authentication = new PasswordAuthentication(user, password);
    Properties props = new Properties();
    props.put("mail.user", user);
    props.put("mail.host", host);
    props.put("mail.debug", debug ? "true" : "false");
    props.put("mail.store.protocol", "pop3");
    props.put("mail.transport.protocol", "smtp");
    session = Session.getInstance(props, this);
  }

  :
}

To provide the authentication support, the getPasswordAuthenticator() method has to be overridden. Since this application would not provide its own implementation, this method would just return an object of type PasswordAuthentication.

public class MailClient extends Authenticator
{
 protected String from;
  protected Session session;
  protected PasswordAuthentication authentication;
  protected Folder rootFolder,currentFolder;
  protected Store store;

  public MailClient(String user, String host, boolean debug,String password)
  {
    from = user + '@' + host;
    authentication = new PasswordAuthentication(user, password);
    Properties props = new Properties();
    props.put("mail.user", user);
    props.put("mail.host", host);
    props.put("mail.debug", debug ? "true" : "false");
    props.put("mail.store.protocol", "pop3");
    props.put("mail.transport.protocol", "smtp");
    session = Session.getInstance(props, this);
  }
  public PasswordAuthentication getPasswordAuthentication()
  {
    return authentication;
  }

  :
}

The next step is to connect to the store.

public class MailClient extends Authenticator
{
 protected String from;
  protected Session session;
  protected PasswordAuthentication authentication;
  protected Folder rootFolder,currentFolder;
  protected Store store;

  public MailClient(String user, String host, boolean debug,String password)
  {
    from = user + '@' + host;
    authentication = new PasswordAuthentication(user, password);
    Properties props = new Properties();
    props.put("mail.user", user);
    props.put("mail.host", host);
    props.put("mail.debug", debug ? "true" : "false");
    props.put("mail.store.protocol", "pop3");
    props.put("mail.transport.protocol", "smtp");
    session = Session.getInstance(props, this);
  }
  public PasswordAuthentication getPasswordAuthentication()
  {
    return authentication;
  }
 public boolean connectToStore()
    {
     boolean connected=false;
      try
      {
        store = session.getStore();
        store.connect();
        rootFolder = store.getDefaultFolder();
        openFolder("INBOX");
        connected=true;
      }
      catch (NoSuchProviderException e)
      {
        e.printStackTrace();
      }
      catch (MessagingException e)
      {
        e.printStackTrace();
      }
        return connected;
    }

  :
}

Once the connection to the store has been established, to extract the messages, the folder has to be opened. That is done like this:

public class MailClient extends Authenticator
{
 protected String from;
  protected Session session;
  protected PasswordAuthentication authentication;
  protected Folder rootFolder,currentFolder;
  protected Store store;

  public MailClient(String user, String host, boolean debug,String password)
  {
    from = user + '@' + host;
    authentication = new PasswordAuthentication(user, password);
    Properties props = new Properties();
    props.put("mail.user", user);
    props.put("mail.host", host);
    props.put("mail.debug", debug ? "true" : "false");
    props.put("mail.store.protocol", "pop3");
    props.put("mail.transport.protocol", "smtp");
    session = Session.getInstance(props, this);
  }
  public PasswordAuthentication getPasswordAuthentication()
  {
    return authentication;
  }
 public boolean connectToStore()
    {
     boolean connected=false;
      try
      {
        store = session.getStore();
        store.connect();
        rootFolder = store.getDefaultFolder();
        openFolder("INBOX");
        connected=true;
      }
      catch (NoSuchProviderException e)
      {
        e.printStackTrace();
      }
      catch (MessagingException e)
      {
        e.printStackTrace();
      }
        return connected;
    }
 public boolean openFolder(String folder)
  {
   boolean isOpenend=false;
    try
    {
      currentFolder = rootFolder.getFolder(folder);
      currentFolder.open(Folder.READ_WRITE);
      isOpenend=true;
    }
    catch (MessagingException e)
    {
      e.printStackTrace();
    }
   return isOpenend;
  }
  
}

That’s it. This class can now connect to a mail server. In this case, it connects to an Apache James Server. And this brings this discussion to its conclusion. In this part the discussion was focused on the basics of Java Mail. The next part will focus on APIs that help applications send huge amounts of data, and on how to actually achieve this end. Till next time.