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Framework Deliverables

Note that the JavaMail Reference Implementation includes DataContentHandlers for some basic data types used in mail messages.

Framework Core Classes

interface DataSource: The DataSource interface provides the JavaBeans Activation Framework with an abstraction of some arbitrary collection of data. It provides a type for that data as well as access to it in the form of InputStreams and OutputStreams where appropriate.

class DataHandler: The DataHandler class provides a consistent interface to data available in many different sources and formats. It manages simple stream to string conversions and related operations using DataContentHandlers. It provides access to commands that can operate on the data. The commands are found using a CommandMap.

interface DataContentHandler: The DataContentHandler interface is implemented by objects that can be used to extend the capabilities of the DataHandler’s implementation of the Transferable interface. Through DataContentHandlers the framework can be extended to convert streams in to objects, and to write objects to streams.

interface DataContentHandlerFactory: This interface defines a factory for DataContentHandlers. An implementation of this interface should map a MIME type into an instance of DataContentHandler. The design pattern for classes implementing this interface is the same as for the ContentHandler mechanism used in java.net.URL.

class CommandMap: The CommandMap class provides an interface to the registry of viewer, editor, print, etc. objects available in the system. Developers are expected to either use the CommandMap implementation included with this package (MailcapCommandMap) or develop their own. Note that some of the methods in this class are abstract.

interface CommandObject: Beans that are Activation Framework aware implement this interface to find out which command verb they’re being asked to perform, and to obtain the DataHandler representing the data they should operate on. Beans that don’t implement this interface may be used as well. Such commands may obtain the data using the Externalizable interface, or using an application-specific method.

class CommandInfo: The CommandInfo class is used by CommandMap implementations to describe the results of command requests. It provides the requestor with both the verb requested, as well as an instance of the bean. There is also a method that will return the name of the class that implements the command but it is not guaranteed to return a valid value. The reason for this is to allow CommandMap implementations that subclass CommandInfo to provide special behavior. For example a CommandMap could dynamically generate Beans. In this case, it might not be possible to create an object with all the correct state information solely from the class name.

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