How do you design and document proxy patterns in UML diagrams?

?? Use UML class diagrams to illustrate these roles and their relationships, along with stereotypes to clarify the roles and functions of the proxy (intermediary), subject (provider of functionality), and client (interactant).

In a proxy pattern, the main participants are: Client: The entity that requires access to the subject. Subject: The common interface implemented by both the RealSubject and Proxy. RealSubject: The actual object that performs the operations. Proxy: The placeholder object that controls access to the RealSubject.

??? A contract between the client and the subject should be defined by an interface that both the proxy and the subject must implement. In UML interface diagrams, dashed lines are used to indicate the realization relationship between the interface and the implementing classes. The proxy should implement this interface in order to delegate client requests to the subject.

Define the common interface that both the RealSubject and Proxy will implement. This ensures that the Client can interact with the Proxy and RealSubject interchangeably.

Implementing the proxy logic is crucial for tailoring its behavior to specific use cases. As highlighted, proxies can offer various functionalities like caching, security, and lazy initialization. The choice of proxy type and its corresponding logic will directly impact how the subject is accessed and interacted with. Visualizing these interactions through UML sequence diagrams can provide a clear understanding of the message flows and object lifespans involved.

Implement the Proxy to control access to the RealSubject. The Proxy can add functionality such as logging, access control, lazy initialization, etc.

?? Proxy Logic: Adapt the proxy's functionality to its type. For instance, a cache proxy stores results to reduce latency, a protection proxy enforces security checks, and a virtual proxy creates subjects on demand. In UML sequence diagrams, arrows represent messages and lifelines represent objects in interactions between the proxy, subject, and client.

Documenting the proxy pattern is essential for understanding its purpose, usage scenarios, and potential implications. By clearly outlining its intent, applicability, benefits, drawbacks, and variations, you can effectively communicate its value and guide its implementation in different contexts. UML notes and comments can be used to provide textual explanations linked to specific diagram elements, while UML package diagrams can visually represent the structural relationships between the proxy pattern classes. This comprehensive documentation will serve as a valuable reference for developers and stakeholders alike.

?? Proxy Pattern: Describe the intent, applicability, advantages, drawbacks, and variations of the proxy pattern in document. Provide textual explanations using UML notes or comments with brackets, and use UML package diagrams to illustrate your proxy pattern classes' structure and dependencies with rectangles.

Once I was in this scenario: You're building an application that displays images from a remote server. Loading images can be slow, especially for users with slower internet connections. Solution: Use a proxy pattern to create a caching layer between your application and the remote image server. How it works: ImageInterface: Defines a common interface for retrieving images. RealImage: The actual implementation that fetches images from the remote server. ImageProxy: The proxy that handles caching. Benefits: Improved performance, Reduced network traffic, Flexibility.