Java EE Notes: email

In this post, I will build on the previous post about sending attachments with JavaMail. We will send HTML-formatted email with images that we include as attachments with the email. The protocol also allows to link to images on a webserver, but because spammers use this method to validate working email addresses, most email clients block external images.

The main idea is to include images as attachments like we did before, but now we also include a content-id per image we attach. Use HTML-code to format our email and use the cid: prefix along with the content-id in the src-attribute of the img-tag to refer to the image attachment.

The example code:


// Create new message with mail session.
Message message = new MimeMessage(session);

// Create multipart message.
MimeMultipart multipart = new MimeMultipart();

// Create bodypart.
BodyPart bodyPart = new MimeBodyPart();

// Create the HTML with link to image CID.
// Prefix the link with "cid:".
String str = "<html><h1>Hello</h1>" +
            "<img src=\"cid:image_cid\"></html>";

// Set the MIME-type to HTML.
bodyPart.setContent(str, "text/html");

// Add the HTML bodypart to the multipart.
multipart.addBodyPart(bodyPart);

// Create another bodypart to include the image attachment.
bodyPart = new MimeBodyPart();

// Read image from file system.
DataSource ds = new FileDataSource("C:\\images\\image.png");
bodyPart.setDataHandler(new DataHandler(ds));

// Set the content-ID of the image attachment.
// Enclose the image CID with the lesser and greater signs.
bodyPart.setHeader("Content-ID", "<image_cid>");

// Add image attachment to multipart.
multipart.addBodyPart(bodyPart);

// Add multipart content to message.
message.setContent(multipart);

// Now set the header and send the email.
...

In this post, I'll show you how to configure JavaMail to use the SMTP server of GMail in Glassfish. This way, you avoid hardcoding server addresses in your application and make your application more portable. It also minimalizes the amount of "plumping" code.

Setup Glassfish

First, fire up the admin screen of Glassfish and click on JavaMail Sessions. Then create a new session configuration by clicking "new".

Make sure the following fields are filled in:

JNDI name: mail/<name>
Mail Host: smtp.gmail.com
Default User: <email>
Default Return Address: <email>

The JNDI name must be prefixed with "mail/". Use your GMail email address in last two fields.

Skip the Advanced settings and create additional properties at the bottom of the screen:

mail.smtp.socketFactory.port: 465
mail.smtp.port: 465
mail.smtp.socketFactory.fallback: false
mail.smtp.auth: true
mail.smtp.password: <gmail_password>
mail.smtp.socketFactory.class: javax.net.ssl.SSLSocketFactory

Use your valid GMail password in the password field. Save, and your configuration is ready for use.

Example client to send email with attachments

Next, we create a client to use the newly created JavaMail service in Glassfish. Before we can do that, we need the application server libraries: appserv-rt.jar and javaee.jar. You can find them in the lib directory of your Glassfish installation. Make sure all the libraries are in your build/class-path.

If you still get unresolved classes related to JavaMail, then you might also need the JavaMail libraries, which you can download here.

The example client below builds an email with three attachments from three different sources, and sends the email to two recipients. You have to use MIME-types to indicate the type of attachments. Save the code below as Main.java, compile, and run!


import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.BodyPart;
import javax.mail.Message;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import javax.mail.internet.MimeMessage.RecipientType;
import javax.mail.util.ByteArrayDataSource;
import javax.naming.InitialContext;

public class Main {

    public void runTest() throws Exception {
        InitialContext ctx = new InitialContext();
        Session session =
            (Session) ctx.lookup("mail/<name>");
        // Or by injection.
        //@Resource(name = "mail/<name>")
        //private Session session;

        // Create email and headers.
        Message msg = new MimeMessage(session);
        msg.setSubject("My Subject");
        msg.setRecipient(RecipientType.TO,
                         new InternetAddress(
                         "tony@email.com",
                         "Tony"));
        msg.setRecipient(RecipientType.CC,
                         new InternetAddress(
                         "michelle@email.com",
                         "Michelle"));
        msg.setFrom(new InternetAddress(
                    "jack@email.com",
                    "Jack"));

        // Body text.
        BodyPart messageBodyPart = new MimeBodyPart();
        messageBodyPart.setText("Here are the files.");

        // Multipart message.
        Multipart multipart = new MimeMultipart();
        multipart.addBodyPart(messageBodyPart);

        // Attachment file from string.
        messageBodyPart = new MimeBodyPart();
        messageBodyPart.setFileName("README1.txt");
        messageBodyPart.setContent(new String(
                                   "file 1 content"),
                                   "text/plain");
        multipart.addBodyPart(messageBodyPart);

        // Attachment file from file.
        messageBodyPart = new MimeBodyPart();
        messageBodyPart.setFileName("README2.txt");
        DataSource src = new FileDataSource("file.txt");
        messageBodyPart.setDataHandler(new DataHandler(src));
        multipart.addBodyPart(messageBodyPart);

        // Attachment file from byte array.
        messageBodyPart = new MimeBodyPart();
        messageBodyPart.setFileName("README3.txt");
        src = new ByteArrayDataSource(
            "file 3 content".getBytes(),
            "text/plain");
        messageBodyPart.setDataHandler(new DataHandler(src));
        multipart.addBodyPart(messageBodyPart);

        // Add multipart message to email.
        msg.setContent(multipart);

        // Send email.
        Transport.send(msg);
    }

    public static void main(String[] args) {
        Main cli = new Main();
        try {
            cli.runTest();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Java EE Notes

Sunday, April 18, 2010

Sending HTML email with images with JavaMail API

Tuesday, April 13, 2010

Using JavaMail API with Glassfish and GMail