Proxy Design pattern - Sequence Diagram

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Proxy Design Pattern: Sequence Diagram Explained

Visualizing how objects communicate over time is one of the best ways to master structural design patterns. A Sequence Diagram for the Proxy Design Pattern illustrates the exact step-by-step chronological interaction between the Client, the Proxy object, and the underlying Real Subject.

Step-by-Step Flow of the Sequence Diagram

• 1. Client Invocation: The client triggers an operation by calling a method on the Proxy instance, expecting standard service execution.
• 2. Interception & Pre-Processing: The Proxy intercepts the incoming message to handle intermediate responsibilities—such as permission verification, caching lookups, logging, or lazy instantiation.
• 3. Delegation to Real Subject: If all validations pass, the Proxy forwards the request to the target Real Subject method.
• 4. Processing & Return: The Real Subject performs the heavy lifting and returns the result back to the Proxy.
• 5. Post-Processing & Client Delivery: The Proxy can apply post-processing before returning the final response to the client.

Why Sequence Diagrams Are Essential for Developers

1. Clarifies Dynamic Behavior: Unlike static class diagrams, sequence diagrams show exact runtime message ordering and lifelines.
2. Exposes Interception Logic: Makes it immediately obvious where security, caching, or remote networking hooks take place.
3. Simplifies Code Implementation: Provides a clear blueprint for writing clean, decoupled Java code.

Recommended Related Tutorials

Enhance your UML and software design skills with these related guides from our channel:

• Flyweight Design Pattern: Sequence Diagram Explained
• Proxy Design Pattern: Class Diagram Explained
• Proxy Design Pattern: Key Points

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Proxy Design pattern - Sequence 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 - Class 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