JavaMail quick start

Send and receive email with the JavaMail APIs

By Tony Loton, JavaWorld.com, 10/26/01

In my own pet project, a talking email client reads -- that is, speaks -- incoming messages. It's based on a refinement of an idea I introduced in "Talking Java!" I'll tell you more about it later.

For now, start by installing and configuring the JavaMail software.

Setup

If you use Java 2 Platform, Enterprise Edition (J2EE) 1.3, you're in luck: it includes JavaMail, so no additional setup is required. If, however, you're running Java 2 Platform, Standard Edition (J2SE) 1.1.7 and upwards, and you want email capability for your applications, download and install the following:

• JavaMail
• JavaBeans Activation Framework

To install, simply unzip the downloaded files and add the contained jar files to your classpath. As an example, here's my classpath for this project:

.;C:\Apps\Java\javamail-1.2\mail.jar;C:\Apps\Java
\javamail-1.2\mailapi.jar;C:\Apps\Java\javamail-1.2
\pop3.jar;C:\Apps\Java\javamail-1.2\smtp.jar;C:\Apps
\Java\jaf-1.0.1\activation.jar

The mailapi.jar file contains the core API classes, while the pop3.jar and smtp.jar files contain the provider implementations for the respective mail protocols. (We won't use the imap.jar file in this article.) Think of the provider implementations as similar to JDBC (Java Database Connectivity) drivers, but for messaging systems rather than databases. As for the mail.jar file, it contains each of the above jar files, so you could restrict your classpath to just the mail.jar and activation.jar files.

The activation.jar file allows you to handle MIME (Multipurpose Internet Mail Extensions) types accessible via binary data streams. Look for the DataHandler class in the Not Just Plain Text section later.

For the record, the rest of this article does not offer comprehensive API coverage; rather, you will learn by doing. If it's in-depth API information you're looking for, then look at the PDF files and Javadocs included in the respective download bundles.

Once you've installed the software, you need to get email account details to run the examples that follow. You'll need your ISP's SMTP (Simple Mail Transfer Protocol) server name and POP (Post Office Protocol) server name, your email account login name, and your mailbox password. Figure 1 shows my details -- not the real ones, you understand -- as used by Microsoft Outlook.

Figure 1. Tony's Internet mail settings

Sending email via SMTP

The first example shows how to send a basic email message via SMTP. Below, you'll find the SimpleSender class, which takes your message's details from the command line and calls a separate method -- send(...) -- to send it:

package com.lotontech.mail;
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
/**
  * A simple email sender class.
  */
public class SimpleSender
{
  /**
    * Main method to send a message given on the command line.
    */
  public static void main(String args[])
  {
    try
    {
      String smtpServer=args[0];
      String to=args[1];
      String from=args[2];
      String subject=args[3];
      String body=args[4];
      send(smtpServer, to, from, subject, body);
    }
    catch (Exception ex)
    {
      System.out.println("Usage: java com.lotontech.mail.SimpleSender"
       +" smtpServer toAddress fromAddress subjectText bodyText");
    }
    System.exit(0);
  }

Next, run SimpleSender as below. Replace smtp.myISP.net with your own SMTP server, as derived from your mail settings:

> java com.lotontech.mail.SimpleSender smtp.myISP.net bill@lotontech.com ben@lotontech.com "Hello" "Just to say Hello."

And, if it works, at the receiving end you'll see something like what's shown in Figure 2.

Figure 2. Message received from SimpleSender

The send(...) method completes the SimpleSender class. I'll show the code first, then detail the theory:

  /**
    * "send" method to send the message.
    */
  public static void send(String smtpServer, String to, String from
   , String subject, String body)
  {
    try
    {
      Properties props = System.getProperties();
      // -- Attaching to default Session, or we could start a new one --
      props.put("mail.smtp.host", smtpServer);
      Session session = Session.getDefaultInstance(props, null);
      // -- Create a new message --
      Message msg = new MimeMessage(session);
      // -- Set the FROM and TO fields --
      msg.setFrom(new InternetAddress(from));
      msg.setRecipients(Message.RecipientType.TO,
        InternetAddress.parse(to, false));
      // -- We could include CC recipients too --
      // if (cc != null)
      // msg.setRecipients(Message.RecipientType.CC
      // ,InternetAddress.parse(cc, false));
      // -- Set the subject and body text --
      msg.setSubject(subject);
      msg.setText(body);
      // -- Set some other header information --
      msg.setHeader("X-Mailer", "LOTONtechEmail");
      msg.setSentDate(new Date());
      // -- Send the message --
      Transport.send(msg);
      System.out.println("Message sent OK.");
    }
    catch (Exception ex)
    {
      ex.printStackTrace();
    }
  }
}

First, notice that you're obtaining a mail session (java.mail.Session), without which you can do nothing. In this case you're calling Session.getDefaultInstance(...) to get a shared session, which other desktop applications may reuse; you can also set up an entirely new session -- via the Session.getInstance(...) method -- that would be unique to your application. The latter could prove important for email clients not isolated on a per-user basis, such as a Web-based email system implemented with servlets.

Establishing a session requires you to set certain properties; at minimum, you need the mail.smtp.host property if you're sending messages via SMTP. You'll find other properties described within the API documentation.