SimpleDynamicProxy.java

package thinkinginjava.typeinfo;

import java.lang.reflect.*;

/*
 * InvocationHandler is the interface implemented by the invocation handler of a proxy instance. 
 * Each proxy instance has an associated invocation handler. When a method is invoked on a proxy instance, 
 * the method invocation is encoded and dispatched to the invoke method of its invocation handler.
 */
class DynamicProxyHandler implements InvocationHandler {
    private Object proxied;

    public DynamicProxyHandler(Object proxied) {
        this.proxied = proxied;
    }

    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable {
        System.out.println("**** proxy: " + proxy.getClass() + ", method: "
                + method + ", args: " + args);
        if (args != null)
            for (Object arg : args)
                System.out.println("  " + arg);
        return method.invoke(proxied, args);
    }
}

class SimpleDynamicProxy {
    public static void consumer(Interface iface) {
        iface.doSomething();
        iface.somethingElse("bonobo");
    }

    public static void main(String[] args) {
        RealObject real = new RealObject();
        consumer(real);

        // Insert a proxy and call again:
        Interface proxy = (Interface) Proxy.newProxyInstance(
                Interface.class.getClassLoader(),
                new Class[]{Interface.class}, new DynamicProxyHandler(real));
        consumer(proxy);
    }
}