TestInvocationHandlerProxying.java

import com.cpox.model.partner.Partner;
import net.bytebuddy.ByteBuddy;
import net.bytebuddy.implementation.FieldAccessor;
import net.bytebuddy.implementation.InvocationHandlerAdapter;
import net.bytebuddy.implementation.MethodDelegation;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Date;

import static net.bytebuddy.matcher.ElementMatchers.isClone;
import static net.bytebuddy.matcher.ElementMatchers.isEquals;
import static net.bytebuddy.matcher.ElementMatchers.isGetter;
import static net.bytebuddy.matcher.ElementMatchers.isHashCode;
import static net.bytebuddy.matcher.ElementMatchers.named;
import static net.bytebuddy.matcher.ElementMatchers.not;

/**
 * Simple proxying using Byte Buddy.
 * <p>
 * All methods of the Partner class are delegated to the original proxied object, except String getters that are
 * handled by the Invocation Handler.
 * <p>
 * Decided not to use this in production because there are simpler ways to handle LOV internal to screen value
 * using BeanUtils and cloning the Partner object, then replacing the defined String fields.
 */
public class TestInvocationHandler {

	private static final Logger LOG = LoggerFactory.getLogger(TestInvocationHandler.class);

	protected interface MyProxyInterface {
		void setInvocationHandler(MyHandler handler);

		Partner getProxied();

		void setProxied(Partner partner);
	}

	protected static class MyHandler implements InvocationHandler {
		@Override
		public Object invoke(final Object o, final Method method, final Object[] objects) throws Throwable {
			LOG.debug("Invoked: {}", method.getName());
			return method.invoke(((MyProxyInterface) o).getProxied(), objects);
		}
	}

	@Test
	public void testApache() throws IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
		final Class<? extends Partner> a = new ByteBuddy()
				.subclass(Partner.class)
				.defineField("invocationHandler", MyHandler.class)
				.defineField("proxied", Partner.class)
				.implement(MyProxyInterface.class)
				.intercept(FieldAccessor.ofBeanProperty())
				// delegate String getters to invocationHandler
				.method(isGetter(String.class))
				.intercept(InvocationHandlerAdapter.toField("invocationHandler"))
				// delegate everything else to the proxied instance
				.method(not(
						isGetter(String.class)
								.or(named("setInvocationHandler"))
								.or(named("setProxied"))
								.or(named("getProxied"))
								.or(isEquals())
								.or(isHashCode())
								.or(isClone())
				))
				.intercept(MethodDelegation.toField("proxied"))
				.make()
				.load(TestInvocationHandler.class.getClassLoader())
				.getLoaded();
//		for (int i = 0; i < 10; i++) {
		final Partner partner = new Partner();
		partner.setGender("My Gender");
		partner.setDateOfBirth(new Date());
		final Partner proxy = a.newInstance();
		((MyProxyInterface) proxy).setInvocationHandler(new MyHandler());
		((MyProxyInterface) proxy).setProxied(partner);
//		a.getDeclaredField("invocationHandler").set(proxy, new MyHandler(p));
//		a.getDeclaredField("partner").set(proxy, p);
		System.out.println(" " + proxy.getGender());
		System.out.println(" " + proxy.getDateOfBirth());
//		}
	}
}