Package com.valescom.support.subscription.java

The subscription package provides a basis for implementing the publish/subscribe model.

See:
Description

Interface Summary

Publication	Responsibility: Providing an interface for all publications to which a Subscriber can subsribe.
Subscriber	Responsibility: Indicating that an Object is a Subscriber.
Subscription	Responsibility: Providing an interface for Objects that define an interest in Publications.
Subscriptions	Responsibility: Providing an interface for maintaining Subscriptions for Subscribers.
SubscriptionVisitor	Responsibility: Providing an interface for a Subscription Visitor.

Class Summary

BasePublication	Responsibility: Providing a base implementation of the Publication interface.
BaseSubscriptions	Responsibility: Providing a base implementation of the Subscriptions interface
Categories	Responsibility: Representing the catagories of a Publication and acting as a Subscription, which evaluates to true if the Catagories are equal.
Expression	Responsibility: Providing an implementation of Subscription, that evaluates an expression (Expr).
ExprSubscriptions	Responsibility: Managing Expressions and Categories.
SynchronizedSubscriptions	Responsibility: Synchronizing all Subscriptions methods.

Exception Summary

ExprException

Responsibility: Indicating that a String Expression can not be parsed.

Package com.valescom.support.subscription.java Description

The subscription package provides a basis for implementing the publish/subscribe model. This model is very similar to the model defined in the com.valescom.support.observer.java package, except that it is more sophisticated. This subscription package is heavily used in the com.valescom.support.event.java package.

Subscribers register an interest in a specific publication by means of a Subscription. A Subscription is either a boolean expression based on a set of Categories (Expression) or the set of Categories itself. Each Publication is accompanied by such a set of Categories.

Subscribers catch a Publication when one of their subscriptions evaluates to true.

Subscribers do not know about each other, but communicate via Publication. This enables a loose coupling between subscribers and eases up the development of relatively independent components.

Use a Subscriptions implementation to (un)subscribe subscribers from and to subscriptions. This implementation can also be used to determine which subscribers are interested in a specific publication.

Design Rules

• To create a special subscriber implement the Subscriber interface.
• To create a special subscription implement the Subscription interface.
• To create a special publication implement the Publication interface or extend the BasePublication class.
• To create a special subscriptions database implement the Subscriptions interface or extend the BaseSubscriptions class.