Proxy Pattern: Adding Control to Object Access Without Changing the Original Code

In software engineering, there are times when we need to control access to an object without modifying its structure or behavior. This is where the Proxy Pattern becomes highly valuable.

Described in the book Design Patterns: Elements of Reusable Object-Oriented Software by the Gang of Four, the Proxy Pattern is a structural design pattern that provides a placeholder or surrogate for another object to control access to it.

Key Use Cases

• Lazy initialization (e.g., creating expensive objects only when needed)
• Access control (e.g., permission checks before delegating calls)
• Remote proxies (e.g., accessing objects in a different address space)
• Logging, caching, or monitoring behavior around the real object

Java Example

Let’s say we have a VideoService interface that defines a method for loading videos.

Step 1: The Interface and Real Object

Step 2: The Proxy Object

Step 3: Usage

Why Use the Proxy Pattern

• It adds a layer of control between the client and the real object.
• It allows you to extend behavior (like caching, logging, access control) without changing the original class.
• It supports separation of concerns, keeping logic like security or resource management outside the core object.

Final Thoughts

The Proxy Pattern is a clean and effective way to introduce cross-cutting concerns around an object, especially when modifying the original class is not desirable or possible.

It’s particularly useful in distributed systems, security layers, and performance-sensitive applications.

#SoftwareEngineering #DesignPatterns #Java #ProxyPattern #Architecture #CleanCode