Proxy Design pattern - Class Diagram

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Proxy Design Pattern: Class Diagram Explained

A class diagram provides the foundational structural blueprint for understanding how classes and interfaces connect in a design pattern. In the Proxy Design Pattern, the class diagram demonstrates how a surrogate object maintains the same contract as the actual service object, allowing seamless substitution without rewriting client code.

Key Participants in the Class Diagram

• Subject (Interface / Abstract Class): Declares the common interface implemented by both the real subject and the proxy. This guarantees that the proxy can substitute for the real object seamlessly.
• RealSubject: The underlying class containing the actual business logic, resource-heavy operations, or sensitive tasks.
• Proxy: Implements the Subject interface, maintains a reference to the RealSubject, and controls access to it (e.g., adding caching, lazy loading, logging, or security checks).
• Client: Interacts exclusively with the Subject interface, remaining oblivious to whether it is talking directly to the RealSubject or the Proxy.

Relationships & Structural Insights

1. Interface Implementation: Both RealSubject and Proxy share an "is-a" implementation relationship with Subject.
2. Composition / Association: The Proxy holds a "has-a" reference to RealSubject, enabling dynamic delegation at runtime.
3. Polymorphic Usage: The client depends strictly on abstraction, ensuring clean compliance with the Open/Closed Principle.

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Proxy Design pattern - Class Diagram

See also:

Proxy Design Pattern - Introduction

Proxy Design pattern - Real Time Example[ATM]

Proxy Design pattern - Real Time Example [Proxy Server]

Proxy Design pattern - Sequence Diagram

Proxy Design pattern - Implementation [Protection Proxy]

Proxy Design pattern - Implementation [Remote Proxy]

Proxy Design pattern - Implementation[Virtual Proxy]

Proxy Design Pattern - Key Points

All Design Patterns Links