Recap: Proxy Pattern

Proxy places a stand-in with the real object's interface in front of it, to control the calls that reach it.

• Intent. Provide a surrogate or placeholder for another object to control access to it.
• Participants. The subject interface, the real subject, the proxy that holds or creates it, and the client.
• Four kinds. Virtual creates on first use, protection checks permission, remote forwards over the network, caching returns a stored result.
• Against Decorator. The same shape; a proxy controls access to one subject and often creates it, while decorators add stackable features to an object they are handed.
• In the wild. JavaScript's Proxy with its traps; Python's __getattr__, which does not forward special methods.
• The trap. Self-calls inside the real object skip the proxy, which is why Spring's @Transactional fails on them.