JavaBeans Activation Framework

Introduction

In computer programming, JavaBeans Activation Framework, or JAF, 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 you 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.

• JSR-925
• Latest spec version is 1.1
• It's an old spec released on April 2006
• It's originally an extension API
  • Now available as a standard API in Java SE and Java EE
  • Has only one package javax.activation (4 interfaces, 13 classes)

Datasource Interface

• Provides access to an arbitrary collection of data
• Get name of the data, data-type name (content type), and the data itself asInputStream or OutputStream
• 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);

...

JAF in use

• REST easy with the JavaBeans Activation Framework
  • http://www.javaworld.com/javaworld/jw-10-2007/jw-10-resteasy.html
• Example also available in Java' 6™ New Features: A Tutorial' book, chapter-13 ISBN 0-9752128-8-5
• Other presentation deck: http://www.hilbertinc.com/whitepapers/JAF.pdf

References

External links

• JSR 925: JavaBeans™ Activation Framework 1.1 Specification
• JavaBeans Activation Framework official page
• Introduction to JavaBeans Activation Framework
• http://www.javaworld.com/javaworld/jw-10-2007/jw-10-resteasy.html
• http://www.hilbertinc.com/whitepapers/JAF.pdf