J2EE Design Pattern : Presentation Tier Patterns : Context Object Design Pattern

• Context Object Design Pattern?
• Example for Context Object

Context Object avoid using protocol specific system information outside of its relevant context.

Context

An application typically uses system information, such as request, configuration, and security data, throughout the lifecycle of a request and response. Aspects of this system information are accessed based on their relevance to a certain processing context.

Problem

When application-specific components and services are exposed to system information that is outside their context, flexibility and reusability of these components are reduced.

Solution

Use a Context Object to encapsulate state in a protocol -independent way to be shared throughout your application.

Encapsulating system data in a Context Object allows it to be shared with other parts of the application without coupling the application to a specific protocol.

Context Object Class Diagram

Participants and Responsibilities

Client

It creates an object with ProtocolInterface.

ProtocolInterface

It is an object that exposes protocol or tier-specific details.

ContextFactory

A ContextFactory creates a protocol- and tier-independent ContextObject.

ContextObject

ContextObject is a generic object used to share domain-neutral state throughout an application.