Plugin

Links classes during configuration rather than compilation.

• Overview
• How It Works
• When to Use It

Overview

Configuration shouldn’t be scattered troughout your application, nor should it require a rebuild ir redeployment. Plugin solves both problems by providing a centralized, runtime configuration.

How It Works

• First define with a Separated Interface any behaviors that will have different implementations based on runtime environment.

• The Plugin will use a basic factory pattern, but it requires its linking instructions to be stated at a single, external point, in order that configuration can be easily managed.

• Additionally, the linking to implementations must occur dynamically at runtime rather than during compilation, so that reconfiguraiton won’t require a rebuild. A text file works quite well as the means of stating linking rules. The Plugin factory will simply read the text file, look for an entry specifying the implementation of a requested interface, and return that implementation.

• Plugin works best in a language that supports reflection because the factory can construct implementations without compile-time dependencies on them. When using reflection, the configuration file must contain mappings of interface names to implementation class names. The factory can sit independently in a framework package and enedn’t be changed when you add new implementations to your configuration options.

When to Use It

Use Plugin whenever you have behaviors that require different implementations based on runtime environment.