Simple example on how to create proxies

ProxyTest.java

package com.learnquest;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Logger;

public class ProxyTest {

	public static void main(String[] args) throws Exception {
		ICalculator calc = (ICalculator) ObjectFactory.create(Calculator.class);
		System.out.println(calc.getClass().getName());
		int result = calc.add(100, 200);
		List names = (List) ObjectFactory.create(ArrayList.class);
		names.add("alice");

	}

}

class ObjectFactory {
	public static Object create(Class clazz) throws Exception {
		Object targetObject = clazz.newInstance();
		Object proxyInstance = Proxy.newProxyInstance(clazz.getClassLoader(),
				clazz.getInterfaces(), new LoggingAspect(targetObject));
		return proxyInstance;
		// return clazz.newInstance();
	}
}

class LoggingAspect implements InvocationHandler {
	private Logger logger;
	private Object target;

	public LoggingAspect(Object target) {
		this.target = target;
		logger = Logger.getLogger(target.getClass().getName());
	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		StringBuffer buff = new StringBuffer();
		buff.append(method.getName() + " is called with arguments ");
		if (args != null) {
			for (Object object : args) {
				buff.append(object).append(" , ");
			}
		}
		logger.info(buff.toString());
		// call the target object
		Object result = method.invoke(target, args);
		logger.info("method " + method.getName() + " returned a result of "
				+ result);
		return result;
	}

}

interface ICalculator {

	public abstract int add(int x, int y);

}

class Calculator implements ICalculator {
	@Override
	public int add(int x, int y) {
		return x + y;
	}
}