1.5 KiB
Proxy Design Pattern — Java Example
Pattern: Structural → Proxy Article: https://ankurm.com/proxy-design-pattern-java/
What this example shows
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/