Java Network Programming, Second Edition

The Message Class

The javax.mail.Message class is the abstract superclass for all individual emails, news postings, and similar messages:

public abstract class Message extends Object implements Part

There’s one concrete Message subclass in the standard JavaMail API, javax.mail.internet.MimeMessage . This is used for both email and Usenet news messages. Service providers are free to add classes for their own message formats. For instance, IBM might provide a NotesMessage class for Lotus Notes.

The Message class mainly declares abstract getter and setter methods that define the common properties of most messages. These properties include the addressees of the message, the recipients of the message, the subject and content of the message, and various other attributes. You can think of these as properties of the envelope that contains the message.

Furthermore, the Message class implements the Part interface. The Part interface mostly handles the body of an email message. It declares methods for getting and setting the content type of the message body, getting and setting the actual message body content, getting and setting arbitrary headers from the message, and getting input streams that are fed by the message body. The main body part of a message can contain other parts. This is used to handle attachments, message bodies that are available in multiple formats, and other multipart emails. Since the Message class is abstract and needs to be subclassed by concrete classes such as MimeMessage ...