proxy - Harsh4999/Design-Patterns GitHub Wiki

Proxy

Use

Proxy acts on behalf of the object and is used for lots of reasons some of the main reasons are protections proxy, remote proxy and virtual proxy.
When we want an object which can work in place of an object
Client is unaware of existence of proxy
Lazy loading uses proxy

Subject interface = Used by client has some operation
Real subject = Implementation of subject interface with method definition
Proxy = Implements subject and maintains a reference of actual object for providing actual functionality.

Proxy must implement same interface as real subject
We can either create actual object later when required or ask for one in constructor
In method implementations of proxy we implement the functionality before delegating to real object
To provide client with instance of a proxy we can provide them factory
There a 2 types of proxies 1) Static 2) Dynamic
When we want to absolutely hold on to the object till we need it hence saving memory and processor this is useful
Dynamic proxy allows us to create proxies at runtime
Dynamic proxy will help in changing classes for proxy in runtime
How the proxy gets hold of real object depends on use case we must ensure to not initialize object unless and until its absolutely necessary
Proxy can cache some state till object is not made
When using proxy we must check for sync
Eg: Hibernate uses proxy for lazy loading while virtual loading