Jakarta Activation

Jakarta Activation (JAF; formerly JavaBeans Activation Framework) is a Jakarta EE API that enables developers to:[1]

  • determine the type of an arbitrary piece of data,
  • encapsulate access to it,
  • discover the operations available on it and
  • to instantiate the appropriate bean to perform the operation(s).

It also enables developers to dynamically register types of arbitrary data and actions associated with particular kinds of data. Additionally, it enables a program to dynamically provide or retrieve JavaBeans that implement actions associated with some kind of data. Originally an extension API, it was available as a standard API in Java SE (from Java SE 6 on) and Java EE, but was removed in Java SE 11.

DataSource Interface
  • Provides access to an arbitrary collection of data
  • Get name of the data, data-type name (content type), and the data itself as Input Stream or Output Stream
  • Two implementation classes provided
    • URLDataSource simplifies the handling of data described by URLs
    • FileDataSource simple DataSource object that encapsulates a file provides data typing services -> delegated to a FileTypeMap object.
  • Other implementations
    • javax.mail.internet.MimePartDataSource
    • javax.mail.util.ByteArrayDataSource

DataContentHandler interface
  • Convert the object to a byte stream and write it to the output stream
  • Convert streams in to objects
  • Used to get object/data which can be transferred
  • Uses java.awt.datatransfer.DataFlavor to indicate the data that can be accessed. DataFlavor is a data format as would appear on a clipboard, during drag and drop, or in a file system.

CommandMap class
  • An abstract class provides an interface to a registry of command objects available in the system
  • Developer develop their own implementation or use
    • MailcapCommandMap class that implements a CommandMap whose configuration is based on mailcap files (1524)
  • Command list available from a MIME Type is stored in CommandInfo object.

CommandObject interface
  • Interface to be implemented by JavaBeans components that are ActivationFramework aware
  • Simple interface with one method:
    • setCommandContext(String verb, DataHandler dh)

Example: Compose an e-mail with attachment

 
import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.internet.*;
import javax.mail.*;

...

// Create a message.
MimeMessage message = new MimeMessage(session);

...

// Create the Multipart to be added the parts to
Multipart multipart= new MimeMultipart();

// Create and fill the first text message part
MimeBodyPart mbp = new MimeBodyPart();
mbp.setText("Body");
multipart.addBodyPart(mbp);

// Create a file attachment and fill as second message part
MimeBodyPart mbp = new MimeBodyPart();
FileDataSource fds = new FileDataSource("C:\\attachment.zip");
mbp.setDataHandler(new DataHandler(fds));
mbp.setFileName(fds.getName());
multipart.addBodyPart(mbp);

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

...

References
  1. JavaBeans Activation Framework. Retrieved 2020-03-30.
  • Official website
  • JSR 925: JavaBeans Activation Framework 1.2 Specification
  • Introduction to JavaBeans Activation Framework
  • Introductory presentation
  • Hanson, Jeff (October 30, 2007). "REST easy with the JavaBeans Activation Framework". JavaWorld. Retrieved 2020-07-27.
  • Example also available in Java 6 New Features: A Tutorial book, chapter-13 ISBN 0-9752128-8-5
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