Introduction-to-Design-Patternsssss.pptx

It's about Design and Proxy Pattern

1. Introduction to Design Patterns Design patterns are reusable solutions to common software design problems. They provide a structured approach to building robust, maintainable, and scalable applications. Understanding design patterns is crucial for any software developer to write clean, modular, and efficient code. by Light OFC

2. What is the Proxy Pattern? The Proxy Pattern is a structural design pattern that provides a surrogate or placeholder for another object to control access to it. It acts as an intermediary between a client and the real subject, allowing you to perform additional logic before forwarding the request.

3. Motivation for the Proxy Pattern To control and manage access to an object, adding security, caching, or logging functionality. To provide a placeholder for an object that is expensive to create or located remotely. To add additional behavior to an object without modifying its original interface.

4. Structure of the Proxy Pattern The Proxy Pattern consists of four main participants: the Client , the Proxy , the RealSubject , and the Subject interface. The Proxy acts as a surrogate for the RealSubject, controlling access and adding additional functionality. The Proxy maintains a reference to the RealSubject and forwards requests from the Client to the RealSubject. This indirection allows the Proxy to perform additional operations before or after forwarding the request.

5. Proxy Pattern Variations Remote Proxy Provides a local representative for an object that resides in a different address space, perhaps on a remote server. This allows clients to interact with the remote object as if it were local. Virtual Proxy Creates expensive objects on demand, controlling and managing their lifecycle. This can improve performance by deferring the creation of objects until they are actually needed. Protection Proxy Controls access to the original object, checking permissions and performing access control before forwarding requests. This can add an extra layer of security to sensitive operations. Smart Reference Proxy Adds additional housekeeping tasks when an object is accessed, such as reference counting, lazy initialization, or automatic locking/unlocking.

6. Advantages of the Proxy Pattern Improved Performance The Proxy can cache frequently accessed data, reducing the load on the original resource and improving overall system performance. Enhanced Security The Proxy can add an extra layer of access control, verifying permissions and protecting the original object from unauthorized access. Simplified Interfaces The Proxy can provide a simplified or customized interface, hiding the complexity of the original object and making it easier to use. Flexibility and Extensibility The Proxy pattern allows you to add new functionality or modify existing behavior without changing the original object's interface.

7. Disadvantages of the Proxy Pattern Increased Complexity Introducing a Proxy can make the overall system more complex, as it adds an additional layer of indirection and abstraction. Performance Overhead The Proxy may introduce a small amount of performance overhead due to the additional method calls and logic it performs. Potential for Misuse If not implemented carefully, the Proxy can be used to hide inappropriate behavior or bypass important checks and validations. Difficulty Debugging The presence of a Proxy can make it more challenging to debug issues, as the additional layer of abstraction can obscure the underlying problem.

8. Real-world Examples of the Proxy Pattern Web Browser Proxy Web browsers often employ a proxy server to cache content, improve security, and provide anonymity for users. The proxy acts as an intermediary, managing access to the internet on the user's behalf. Virtual Machine Proxy In cloud computing, virtual machines may use a proxy to manage network traffic, provide load balancing, and enable secure communication between the VM and external resources. Image Loading Proxy Some websites use a proxy to lazily load images, only fetching them when they are about to be displayed. This improves page load times and reduces bandwidth usage. Access Control Proxy Enterprises may use a proxy to control and monitor access to sensitive internal resources, adding an extra layer of security and compliance checks.

9. Implementing the Proxy Pattern in Code Define the Subject Interface Create an abstract class or interface that defines the common methods to be implemented by the RealSubject and the Proxy. Implement the RealSubject Provide the actual implementation of the Subject interface, containing the core functionality that the client needs to access. Create the Proxy Class Implement the Proxy class, which maintains a reference to the RealSubject and forwards requests from the client to the RealSubject. Add Proxy-specific Functionality Enhance the Proxy with additional behavior, such as caching, access control, or logging, to provide the desired extra functionality. Client Interaction The client interacts with the Proxy object, which in turn interacts with the RealSubject, handling the request and any additional logic.

10. Conclusion and Key Takeaways In summary, the Proxy Pattern is a powerful structural design pattern that allows you to control and manage access to an object, providing additional functionality such as security, caching, and logging. By introducing an intermediary Proxy, you can enhance the original object's capabilities without modifying its core interface.