Proxy Pattern

Preview

1. What is the Proxy Pattern and when is it used in software design?
2. How does the Proxy Pattern improve performance and provide a level of indirection in object communication?
3. What is the difference between a remote proxy and a virtual proxy in the Proxy Pattern?
4. Can multiple proxies be used in a chain to achieve different functionality or security measures?
5. How does the Proxy Pattern relate to other design patterns such as Decorator and Adapter?

Explain

Proxy pattern is a design pattern that provides a substitute or placeholder for another object to control its access, creation, or behavior. A proxy object allows the client to interact with the original object through an interface and provides an additional layer of abstraction for handling the requests and responses to the original object.

A practical example of the proxy pattern is the use of a cache proxy for a web application. The proxy object intercepts requests from the client and checks if the requested data is available in the cache, if it is present in the cache, the proxy object returns the data, if not, it delegates the request to the original object and caches the response for future use. This pattern helps in reducing the response time of the application and minimizes the number of requests made to the original object.

Keypoint

1. Proxy pattern acts as a surrogate for another object to control access to it.
2. It is used to provide a representative object that can handle calls made to the original object from a client.
3. The proxy forwards requests to the real object and can perform additional tasks before or after passing on the requests.
4. The pattern can be used to implement system security, caching, lazy loading, and remote access by passively intercepting and modifying incoming requests.
5. The pattern separates the concerns of the client from the implementation details of the object being accessed.
6. The types of proxy pattern include remote proxy, virtual proxy, protection proxy, cache proxy, and smart proxy.
7. The design of the proxy should ensure compatibility and transparency with the original object’s interface.
8. The proxy should not introduce new dependencies, headaches, or performance penalties for the client or real object.

Review

1. What is the Proxy Pattern?

Answer: The Proxy Pattern is a design pattern in software development that provides a surrogate object to control access to another object, called the Real Subject, which may be resource-intensive to create or support.

2. What are the main benefits of using the Proxy Pattern in software development?

Answer: The main benefits of using the Proxy Pattern include improved performance and scalability, increased security and reliability, and better separation of concerns.

3. What are the different types of Proxy Patterns?

Answer: There are four types of Proxy Patterns: Virtual Proxy, Remote Proxy, Protection Proxy, and Smart Proxy.

4. How does Virtual Proxy work?

Answer: Virtual Proxy creates a placeholder for a heavy and expensive object until it is actually needed. It acts as a buffer between the client and the real object, and is responsible for creating and initializing the real object when it is first accessed.

5. What is a common real-world example of the Proxy Pattern?

Answer: A common real-world example of the Proxy Pattern is a proxy server, which acts as an intermediary between a client and a server. The proxy server can cache frequently accessed resources locally, thereby reducing network traffic and improving performance. It can also provide firewall and authentication services to enhance security.