52 lines
1.9 KiB
Java
52 lines
1.9 KiB
Java
package proxy;
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/**
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* Proxy Design Pattern — Runnable Demo
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*
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* Shows two proxy types:
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* 1. Virtual Proxy (lazy connection)
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* 2. Logging Proxy (cross-cutting concern)
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* 3. Proxy chaining (both together)
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*
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* Run: javac proxy/*.java && java proxy.Main
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* Article: https://ankurm.com/proxy-design-pattern-java/
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*/
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public class Main {
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public static void main(String[] args) throws InterruptedException {
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System.out.println("=== Proxy Design Pattern Demo ===\n");
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// --- Virtual Proxy: lazy connection ---
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System.out.println("-- Virtual Proxy (lazy loading) --");
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DatabaseConnection lazy = new LazyConnectionProxy("jdbc:postgresql://localhost/mydb");
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lazy.connect(); // absorbed by proxy, no real connection yet
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System.out.println("(no real connection yet — saved startup time)");
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System.out.println("Result: " + lazy.executeQuery("SELECT * FROM users WHERE id=1"));
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System.out.println("Result: " + lazy.executeQuery("SELECT COUNT(*) FROM orders"));
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lazy.disconnect();
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System.out.println();
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// --- Logging Proxy: wraps the real connection ---
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System.out.println("-- Logging Proxy --");
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DatabaseConnection real = new RealDatabaseConnection("jdbc:mysql://localhost/shopdb");
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real.connect();
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DatabaseConnection logged = new LoggingProxy(real);
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logged.executeQuery("SELECT * FROM products LIMIT 10");
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logged.disconnect();
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System.out.println();
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// --- Proxy chaining: lazy + logging ---
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System.out.println("-- Chained Proxies: Lazy + Logging --");
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DatabaseConnection chain =
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new LoggingProxy(
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new LazyConnectionProxy("jdbc:oracle://localhost/warehouse"));
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chain.connect();
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chain.executeQuery("SELECT SUM(quantity) FROM inventory");
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chain.disconnect();
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System.out.println("\n=== Demo complete ===");
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}
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}
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