Invoker.java

/*
 * Copyright (C) 2011 Christopher Probst
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of the 'FoxNet RMI' nor the names of its 
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.indyforge.foxnet.rmi;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import com.indyforge.foxnet.rmi.binding.RemoteBinding;

/**
 * An invoker can invoke methods synchronously/asynchronously or via a proxy
 * object. Every invoker has an {@link InvokerManager} which is used to send
 * Invocations.
 * 
 * @author Christopher Probst
 */
public final class Invoker implements InvocationHandler {

	/**
	 * @param proxy
	 *            The proxy.
	 * @return the invoker instance of the given proxy or null.
	 */
	public static Invoker of(Object proxy) {
		// Check to be a proxy class
		if (proxy == null || !Proxy.isProxyClass(proxy.getClass())) {
			return null;
		} else {
			// Try to get the handler
			InvocationHandler handler = Proxy.getInvocationHandler(proxy);

			// Conditional return...
			return handler instanceof Invoker ? (Invoker) handler : null;
		}
	}

	// The invoker manager which created this invoker
	private final InvokerManager invokerManager;

	// The remote binding of this invoker
	private final RemoteBinding remoteBinding;

	// The proxy invocation timeout
	private volatile long proxyTimeout;

	// The lazy proxy object which is created when needed
	private volatile Object lazyProxy;

	/**
	 * Creates a new invoker using the given arguments.
	 * 
	 * @param invokerManager
	 *            The invoker manager.
	 * @param remoteBinding
	 *            The remote binding.
	 */
	public Invoker(InvokerManager invokerManager, RemoteBinding remoteBinding) {
		if (invokerManager == null) {
			throw new NullPointerException("invokerManager");
		} else if (remoteBinding == null) {
			throw new NullPointerException("remoteBinding");
		}
		this.invokerManager = invokerManager;
		this.remoteBinding = remoteBinding;
	}

	/**
	 * @return the proxy timeout which is used when invoking proxy methods.
	 */
	public long proxyTimeout() {
		return proxyTimeout;
	}

	/**
	 * Sets the proxy timeout which is used when invoking proxy methods.
	 * 
	 * @param proxyTimeout
	 *            The new proxy timeout. A value <= 0 means waiting without a
	 *            limit.
	 * @return this for chaining.
	 */
	public Invoker proxyTimeout(long proxyTimeout) {
		this.proxyTimeout = proxyTimeout;
		return this;
	}

	/**
	 * @return the invoker manager of this invoker.
	 */
	public InvokerManager manager() {
		return invokerManager;
	}

	/**
	 * @return the remote binding of this invoker.
	 */
	public RemoteBinding binding() {
		return remoteBinding;
	}

	/**
	 * Invokes the method with the given method id and arguments. This method
	 * should not be called directly.
	 * 
	 * @param methodId
	 *            The methodId.
	 * @param arguments
	 *            The arguments.
	 * @return an invocation.
	 */
	public Invocation invoke(int methodId, Object... arguments) {
		// Convert
		invokerManager.localsToRemotes(arguments);

		// Create invocation
		Invocation invocation = new Invocation(this, methodId, arguments);

		// Send the invocation
		invokerManager.sendInvocation(invocation);

		return invocation;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object,
	 * java.lang.reflect.Method, java.lang.Object[])
	 */
	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {

		// Check the proxy class
		if (lazyProxy == null || lazyProxy != proxy) {
			throw new IllegalArgumentException("The given proxy is not "
					+ "the valid proxy of this invoker");
		}

		// Invoke the method remotely
		Invocation invocation = invoke(method, args);

		// Simply synchronize and return or throw
		if (invocation.synchronize(proxyTimeout)) {
			return invocation.attachment();
		} else {
			throw invocation.cause();
		}
	}

	/**
	 * Invokes the given method with the given arguments.
	 * 
	 * @param method
	 *            The method.
	 * @param arguments
	 *            The arguments.
	 * @return an invocation.
	 */
	public Invocation invoke(Method method, Object... arguments) {
		Integer methodId = remoteBinding.methodIds().get(method);
		if (methodId == null) {
			throw new IllegalArgumentException("Unknown method");
		}
		return invoke(methodId, arguments);
	}

	/**
	 * Invokes the method with the given name and arguments.
	 * 
	 * @param methodName
	 *            The method name.
	 * @param arguments
	 *            The arguments.
	 * @return an invocation.
	 */
	public Invocation invoke(String methodName, Object... arguments) {
		Integer methodId = remoteBinding.nameIds().get(methodName);
		if (methodId == null) {
			throw new IllegalArgumentException("Unknown method name");
		}
		return invoke(methodId, arguments);
	}

	/**
	 * @return the proxy object for this invoker.
	 */
	public Object proxy() {
		/*
		 * Use double-check idiom here.
		 */
		Object tmpProxy = lazyProxy;
		if (tmpProxy == null) {
			synchronized (this) {
				tmpProxy = lazyProxy;
				if (tmpProxy == null) {
					lazyProxy = tmpProxy = Proxy.newProxyInstance(Thread
							.currentThread().getContextClassLoader(),
							remoteBinding.interfaces(), this);
				}
			}
		}

		return tmpProxy;
	}
}