Applied Design Patterns with Java

Structural :: Adapter (137) {C ch 9}

Applicability

Use the Adapter pattern when:

• an existing class does not have an interface matching a current need;
• there is a need to create a reusable class that cooperates with unrelated or unforeseen classes (without compatible interfaces);
• (object Adapter only) there are several existing subclasses, but it's impractical to adapt their interface by subclassing them. An object Adapter can adapt the interface of its parent class.

Structure

A class adapter uses multiple inheritance to adapt one interface to another:

An object adapter relies on object composition:


Participants

• Target (Shape) defines the domain-specific interface that Client uses.
• Client (DrawingEditor) collaborates with objects conforming to the Target interface.
• Adaptee (TextView) defines an existing interface that needs adapting.
• Adapter (TextShape) adapts the interface of Adaptee to the Target interface.

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