A DatabaseConnection interface is implemented by a real, expensive connection (RealDatabaseConnection) and by two proxies that sit in front of it: LazyConnectionProxy defers opening the real connection until the first query actually runs (virtual proxy), and LoggingProxy wraps any DatabaseConnection — real or proxied — and adds timing/audit logging around every call (cross-cutting concern proxy). Because both proxies implement the same interface as the real subject, they compose: Main chains LoggingProxy around a LazyConnectionProxy to get lazy loading and logging together.

How to run

javac proxy/*.java -d out/proxy
java -cp out/proxy proxy.Main

Requires Java 25.

Post Section ↔ File Mapping

Post Section	File(s)
The Subject Interface	`DatabaseConnection.java`
The Real Subject	`RealDatabaseConnection.java`
Virtual Proxy: Lazy Initialisation	`LazyConnectionProxy.java`
Logging Proxy: Cross-Cutting Concerns	`LoggingProxy.java`
Wiring It Together: Proxy Chaining	`Main.java`

Note: the "Dynamic Proxy with java.lang.reflect.Proxy" snippet is illustrative only — it is not part of this repository's runnable example.

Article: https://ankurm.com/proxy-design-pattern-java/ All patterns: https://ankurm.com/design-patterns-java/