33 lines
1.5 KiB
Markdown
33 lines
1.5 KiB
Markdown
# Proxy Design Pattern — Java Example
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**Pattern:** Structural → Proxy
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**Article:** https://ankurm.com/proxy-design-pattern-java/
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## What this example shows
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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.
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## How to run
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```bash
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javac proxy/*.java -d out/proxy
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java -cp out/proxy proxy.Main
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```
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Requires Java 25.
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## Post Section ↔ File Mapping
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| Post Section | File(s) |
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|---|---|
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| The Subject Interface | `DatabaseConnection.java` |
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| The Real Subject | `RealDatabaseConnection.java` |
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| Virtual Proxy: Lazy Initialisation | `LazyConnectionProxy.java` |
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| Logging Proxy: Cross-Cutting Concerns | `LoggingProxy.java` |
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| Wiring It Together: Proxy Chaining | `Main.java` |
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Note: the "Dynamic Proxy with java.lang.reflect.Proxy" snippet is illustrative only — it is not part of this repository's runnable example.
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Article: https://ankurm.com/proxy-design-pattern-java/
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All patterns: https://ankurm.com/design-patterns-java/
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