Java Mail API: Transforming Mail into Data Carriers

That was theory. Now let's see it in practice. This application supposes that the XML document reader and writer are already in place. To send the document as an attachment I will add a function to the MailClient.java -- sendDocument(). It takes a filename and the recipient’s address as String and returns a boolean value corresponding to the success or failure of the transfer. For clarity I am including the complete file.

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;
  }
  public boolean sendDocument(String filename, String toAddress,  String from,  String subject, String message)
         {
 :
 :
         }
 
}

First create an object of MimeMesage and set the from and to addresses as well as the subject. Also set the body of the message.

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;
  }
  public boolean sendDocument(String filename, String toAddress, String from,  String subject, String message)
         {
 try
       {
     // create a message
     MimeMessage msg = new MimeMessage(session);
     msg.setFrom(new InternetAddress(from));
     InternetAddress[] address = {new InternetAddress(to)};
     msg.setRecipients(Message.RecipientType.TO, address);
     msg.setSubject(subject);
               
     // create and fill the first message part
     MimeBodyPart mbp1 = new MimeBodyPart();
     mbp1.setText(msgText1);

     // create the second message part
     MimeBodyPart mbp2 = new MimeBodyPart();

 :
 :
     } catch (MessagingException mex) {
     mex.printStackTrace();
     Exception ex = null;
     if ((ex = mex.getNextException()) != null) {
  ex.printStackTrace();
     }

   }
 
}

Then create an object of FileDataSource from the file name. Next, set the data handler for the mbp2 object of MimeBodyPart. The data handler reads the data from the file and gives it to the MimeBodyPart. Here I will just show the function.

public boolean sendDocument(String filename, String toAddress, String from,  String subject, String message)
  {
  try 
  {
     // create a message
     MimeMessage msg = new MimeMessage(session);
     msg.setFrom(new InternetAddress(from));
     InternetAddress[] address = {new InternetAddress(to)};
     msg.setRecipients(Message.RecipientType.TO, address);
     msg.setSubject(subject);
               
     // create and fill the first message part
     MimeBodyPart mbp1 = new MimeBodyPart();
     mbp1.setText(msgText1);

     // create the second message part
     MimeBodyPart mbp2 = new MimeBodyPart();

     // attach the file to the message
        FileDataSource fds = new FileDataSource(filename);
     mbp2.setDataHandler(new DataHandler(fds));
     mbp2.setFileName(fds.getName());

 :
 :
     } catch (MessagingException mex) {
     mex.printStackTrace();
     Exception ex = null;
     if ((ex = mex.getNextException()) != null) {
  ex.printStackTrace();
     }

Then create an object of Multipart, add the two MimeBodyPart objects to it, and send the file using send of the Transport class.

public boolean sendDocument(String filename, String toAddress, String from,  String subject, String message)
   {
   try 
   {
     // create a message
     MimeMessage msg = new MimeMessage(session);
     msg.setFrom(new InternetAddress(from));
     InternetAddress[] address = {new InternetAddress(to)};
     msg.setRecipients(Message.RecipientType.TO, address);
     msg.setSubject(subject);
               
     // create and fill the first message part
     MimeBodyPart mbp1 = new MimeBodyPart();
     mbp1.setText(msgText1);

     // create the second message part
     MimeBodyPart mbp2 = new MimeBodyPart();

     // attach the file to the message
     FileDataSource fds = new FileDataSource(filename);
     mbp2.setDataHandler(new DataHandler(fds));
     mbp2.setFileName(fds.getName());

     // create the Multipart and add its parts to it
     Multipart mp = new MimeMultipart();
     mp.addBodyPart(mbp1);
     mp.addBodyPart(mbp2);

     // add the Multipart to the message
     msg.setContent(mp);

     // set the Date: header
     msg.setSentDate(new Date());
    
     // send the message
     Transport.send(msg);

     } catch (MessagingException mex) {
     mex.printStackTrace();
     Exception ex = null;
           
     if ((ex = mex.getNextException()) != null) {
  ex.printStackTrace();
     return false;
     }
   return true;
}