Java Training Introduction to Java Mail

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Java TrainingIntroduction to Java Mail

• Written by Jeff Smith

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What is JavaMail? -1

• JavaMail is an API for sending and receiving
  email using Java. The current version is 1.3.1
  and can be downloaded from Sun's website at
• http//java.sun.com/products/javamail/
• Possible uses
• Send email from web pages using servlets
• Create a GUI email client
• Send email from Java stored procedures
• Send email from any type of Java application
• Spam your friends and enemies! (read email
  addresses from a database, write a for () loop,
  and away the emails go!)

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What is JavaMail? -2

• To send JavaMail, you'll need to add at least two
  JAR files from Sun to your classpath (placing
  them in a lib directory may be a good idea)
• activation.jar
• mail.jar
• (Note You can download these files from the Java
  Zone)
• For more complex emailing tasks (like receiving
  or managing pop3 or imap mail servers), you'll
  need to download additional files like pop3.jar
  and imap.jar.
• You will also need access to a mail server and
  possibly a username/password for that mail server

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How Does Email Work?

• In general, each internet domain has an email
  server.
• When you send out an email
• Your email client program sends the message to
  your email server
• Your email server contacts the addressee's email
  server using the SMTP (simple mail transfer
  protocol)
• Your email server verifies that the addressee's
  user name is valid
• Your email server then transfers the email to the
  addressee's email server
• When the addressee logs into his email server
  (using his email client program), he gets his
  email

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Mail Servers (sendmail)-1

• sendmail is the most commonly used mail server in
  the world, as it generally comes free with Unix
  and Linux installations
• very powerful and flexible. Supports POP3 and
  IMAP
• well documented (lots of books on setting up
  sendmail)
• long track record (first version appeared in
  early '80s)
• tedious to set up (lots of cryptic configuration
  files)
• free
• www.sendmail.org

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Mail Servers (qmail)-2

• qmail is probably the most popular alternative to
  sendmail in the UNIX world
• perhaps more secure than sendmail (at least older
  versions of sendmail)
• Easier to set up and administer than sendmail
• pretty good documentation (several books written
  on qmail in the past few years)
• free
• http//www.qmail.org/top.html

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Mail Servers (MS Exchange)-2

• MS Exchange is widely used in the Windows world,
  especially in corporate environments that use MS
  Office (and hence MS Outlook)
• Expensive
• Integrated into MS Active Directory
• GUI administration tools are easier to learn for
  Windows people
• MS Outlook is a powerful and slick email program
  that will work with Exchange, sendmail, or qmail.
  It does, however, have a history of security
  vulnerabilities and some organizations refuse to
  use it because of that.

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POP3, IMAP, MAPI -1

• Currently, the most popular protocols are
• POP3 (Post Office Protocol, version 3)
• IMAP (Internet Message Access Protocol)
• MAPI (Messaging Application Programming
  Interface--Microsoft Windows email interface)

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POP3

• POP3 is the oldest and most widely used. It was
  designed to support offline mail processing.
• Mail is delivered to a server and a user's
  computer runs a mail client program to download
  any new mail
• Once messages are delivered, they are generally
  deleted from the mail server
• This minimizes disk space requirements for mail
  server, but ties the mail to a particular
  machine. If user goes to another computer, he
  can't access his mail
• POP3 has limited support for reading mail online
  (and leaving the mail on the mail server)
• Simpler protocol than IMAP makes it easier to
  implement. More POP3 mail clients available

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IMAP

• IMAP
• Developed at University of Washington
• Primarily used to access mail and leave it on the
  mail server. This allows users to access their
  mail from any computer
• Requires more disk space to store email messages
• Can work in "offline" mode like POP3
• Easy to manage multiple mailboxes
• Supports tagging emails with flags like "read",
  "deleted", "answered", etc.

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MAPI

• MAPI
• Set of C functions (API) developed by Microsoft
  and supported in MS Exchange/Outlook
• Also supported by Eudora Mail
• For more info, type the following search string
  in Google"MAPI sitemsdn.microsoft.com"

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Apache James Mail Server

• Apache has a free mail server called James
• Supports POP3, SMTP, and NNTP
• Download the binary file
• .ZIP version (for Windows)
• .TAR version (for Linux)
• Uncompress it and then run run.bat (Windows) or
  run.sh (Linux) to start the mail server
• Download from here
• http//james.apache.org/download.cgi

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NOAA Mail Server

• You can use ESRL/NOAAs email server
• email.boulder.noaa.gov
• mailProperties.setProperty("mail.smtp.host","email
  .boulder.noaa.gov")
• This will work IF you send emails to _at_noaa.gov
  email addresses (like jeff.s.smith_at_noaa.gov)
• When I tried to send an email to
  jeffssmith1_at_yahoo.com I got this error message
• Invalid Address
• Relaying not allowed jeffssmith1_at_yahoo.com

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Using JavaMail -1

• Once you have a mail server you can use (either
  James or another mail server), you can send
  emails through it by using JavaMail
• In general, to send a plain text email using
  JavaMail, you do the following
• Get a mail session instance
• Create a MimeMessage object (passing in the mail
  session instance into the constructor)
• Set the MimeMessage object's properties (like the
  toAddress, fromAddress, message, etc.)
• Send the message

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Getting a Mail Session

• Get a mail session for the James mail server. If
  James is running on your own computer, your
  mail.smtp.host is localhost.
• If your mail server is a remote computer, it
  might be something like mailgate.fsl.noaa.gov
• Get a mail session for the James mail server
• private Session getMailSession() throws Exception
• Properties mailProperties new Properties()
• mailProperties.setProperty("mail.transport.proto
  col",
• "smtp")
• mailProperties.setProperty("mail.smtp.host",
• "localhost")
• return Session.getInstance(mailProperties,
  null)

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Plain Text Email Example

• Next, send your email using the mail session
• MimeMessage msg new MimeMessage(getMailSession()
  )
• msg.setFrom(new InternetAddress("bill.gates_at_msn.co
  m"))
• msg.addRecipient(Message.RecipientType.TO,
• new InternetAddress("larry.ellison_at_oracle.co
  m"))
• msg.setSubject("RE Oracle vs SQL Server")
• msg.setText("SQL Server is better than Oracle")
• Transport.send(msg)

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Exceptions and imports

• Your code which sends an email will need to catch
  the following checked exceptions
• Exception
• MessagingException
• AddressException
• You should import the following packages
• import javax.mail.
• import javax.mail.internet.

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HTML Email

• You can also send HTML email with JavaMail. HTML
  email can be used to
• Use different size fonts
• imbed images into your email
• Use different colored text, bold, italic, etc.

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HTML Email

• With HTML email,
• you set the mime message content type to
  "text/html"
• call the setContent() method to set your html
  content
• It helps to know a little HTML!

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Mail Security

• Virtually all mail servers require a username and
  password to receive email
• Some mail servers require a username and password
  to send an email (by default, James does not).
• This prevents spammers from hijacking the mail
  server to send unauthorized email
• JavaMail supports this username/password
  authorization and authentication
• To implement this, you get a transport object
  from the mail session and call the connect()
  method with the mail host, username, and password
• See next slide for code example

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HTML Email Example

• Example of sending html message with an imbedded
  image using username/password authorization
• MimeMessage msg new MimeMessage(mailSession)
• msg.setFrom(new InternetAddress("bill_at_msn.com"))
• msg.addRecipient(Message.RecipientType.TO, new
• InternetAddress(tom_at_msn.com"))
• msg.setSubject(subject)
• String html "MY SPAM
  
• src'http//www.wrfportal.org/images/NOAA_logo.
  jpg'
• "
• msg.setContent(html, "text/html")
• Transport transport mailSession.getTransport("sm
  tp")
• transport.connect("localhost","user", "passwd")
• msg.saveChanges()
• transport.sendMessage(msg, msg.getAllRecipients())
  
• transport.close()

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Email attachments -1

• To append an email attachment, you need to send a
  "multipart" message
• Create your MimeMessage object as usual, setting
  the from address, to address, subject, etc...
• Create a MimeBodyPart object for your main
  message and set its text (or content) to be your
  message
• Create a MimeMultiPart object for your attachment
  and call its setContent() method to attach your
  file
• Create a Multipart object and add both body parts
  to it.
• Call your MimeMessage's setContent() method,
  passing in your Multipart object
• Call Transport.send() to send the message
• Whew!!!

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Email attachment Example-1
MimeMessage msg new MimeMessage(getMailSession()
) msg.setFrom(new InternetAddress("bill.gates_at_msn
.com")) msg.addRecipient(Message.RecipientType.TO
, new InternetAddress("larry.ellison_at_oracle
.com")) msg.setSubject("RE Oracle vs SQL
Server") //Create the main message (body)
part MimeBodyPart mainBodyPart new
MimeBodyPart() mainBodyPart.setText("Here is my
message")
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Email attachment Example-2
//Create attachment body part MimeBodyPart
attachBodyPart new MimeBodyPart() DataSource
source new FileDataSource("1.jpg") attachBodyPa
rt.setDataHandler(new DataHandler(source)) attach
BodyPart.setFileName("1.jpg") //Now create the
multipart and add the parts Multipart multipart
new MimeMultipart() multipart.addBodyPart(mainBod
yPart) multipart.addBodyPart(attachBodyPart) /
/add the multipart to the original Mime
message msg.setContent(multipart) Transport.send
(msg)
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Exercise -1

• Write a program in package gov.noaa.email that
  reads a list of email recipients from a disk file
  and then sends them each an email message.
• Use your NOAA webmail account to test this (or
  you can use our Yahoo email account)
• You'll need to
• Create a file and populate it with a list of
  email addresses (use your own email address or
  someone else in the class)
• Send a single email to all the recipients you
  read from the db table.
• If you are feeling ambitious, you can send an
  HTML email message.
• Use an email client (NOAA webmail?) to verify
  message delivery
• Extra credit send an email attachment and write
  an Ant script for your project

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JavaMail Summary

• JavaMail is powerful with good support for things
  like HTML and attachments
• But adding an attachment isn't as simple as it
  should be. A nice framework (or helper class)
  would be useful to simplify JavaMail code
• JavaMail also supports
• receiving email
• administering mail servers
• For an article on receiving email via JavaMail,
  see
• http//www.javaworld.com/javaworld/jw-10-2001/jw-1
  026-javamail-p2.html