Proxy

Definition

A proxy is an intermediary or substitute that acts on behalf of another entity to facilitate communication or decision-making processes. In design patterns, the proxy pattern allows an object to represent another object, providing a surrogate or placeholder to control access to it. This is useful for implementing lazy loading, access control, logging, and other functionalities without changing the original object's interface.

5 Must Know Facts For Your Next Test

1. The proxy pattern is often used to control access to a resource that may be expensive to create or use, such as network connections or large data sets.
2. There are different types of proxies, including virtual proxies for lazy loading, protective proxies for access control, and remote proxies for handling requests from remote locations.
3. Implementing a proxy can enhance performance by reducing the number of direct interactions with a resource, which can lead to improved application responsiveness.
4. The proxy pattern helps in encapsulating the complexity of the actual object and can add additional functionalities like logging or security checks without altering the object itself.
5. Using proxies can improve maintainability since changes in the actual object do not directly affect the clients using the proxy.

Review Questions

• How does the proxy pattern help manage resource access and enhance application performance?
  • The proxy pattern helps manage resource access by acting as an intermediary that controls how and when an actual resource is accessed. By using virtual proxies for lazy loading, it delays the creation of heavy resources until they are absolutely needed. This leads to enhanced application performance as it reduces unnecessary resource usage and can improve responsiveness by minimizing load times.
• Discuss the various types of proxies and their specific roles in design patterns.
  • There are several types of proxies, each serving distinct roles in design patterns. Virtual proxies are used for lazy loading, which defers resource creation until necessary. Protective proxies enforce access control by restricting certain operations on an object. Remote proxies handle communication with objects located on different servers or networks, allowing clients to interact with them as if they were local. Each type enhances functionality while maintaining a clean interface.
• Evaluate the impact of implementing the proxy pattern on system architecture and maintenance over time.
  • Implementing the proxy pattern positively impacts system architecture by promoting separation of concerns; it encapsulates complex behaviors behind a simple interface. This improves maintainability because developers can modify or replace the underlying actual object without altering client code. Additionally, since proxies can add features like logging or security checks independently, they allow systems to adapt and evolve more easily over time without significant restructuring.

Related terms

Facade: A design pattern that provides a simplified interface to a complex subsystem, making it easier to use.

Decorator: A structural design pattern that allows behavior to be added to individual objects, either statically or dynamically, without affecting the behavior of other objects from the same class.

Observer: A behavioral design pattern where an object, known as the subject, maintains a list of its dependents, called observers, and notifies them of state changes.