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	/*
	* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.rmi.server;

	import java.io.IOException;
	import java.io.ObjectInput;
	import java.io.ObjectOutput;
	import java.lang.reflect.Proxy;
	import java.net.MalformedURLException;
	import java.net.URL;
	import java.rmi.*;
	import java.rmi.activation.*;
	import java.rmi.server.Operation;
	import java.rmi.server.RMIClassLoader;
	import java.rmi.server.RemoteCall;
	import java.rmi.server.RemoteObject;
	import java.rmi.server.RemoteObjectInvocationHandler;
	import java.rmi.server.RemoteRef;
	import java.rmi.server.RemoteStub;

	@SuppressWarnings("deprecation")
	public class ActivatableRef implements RemoteRef {

	private static final long serialVersionUID = 7579060052569229166L;

	protected ActivationID id;
	protected RemoteRef ref;
	transient boolean force = false;

	private static final int MAX_RETRIES = 3;
	private static final String versionComplaint =
	"activation requires 1.2 stubs";

	/**
	* Create a new (empty) ActivatableRef
	*/
	public ActivatableRef()
	{}

	/**
	* Create a ActivatableRef with the specified id
	*/
	public ActivatableRef(ActivationID id, RemoteRef ref)
	{
	this.id = id;
	this.ref = ref;
	}

	/**
	* Returns the stub for the remote object whose class is
	* specified in the activation descriptor. The ActivatableRef
	* in the resulting stub has its activation id set to the
	* activation id supplied as the second argument.
	*/
	public static Remote getStub(ActivationDesc desc, ActivationID id)
	throws StubNotFoundException
	{
	String className = desc.getClassName();

	try {
	Class<?> cl =
	RMIClassLoader.loadClass(desc.getLocation(), className);
	RemoteRef clientRef = new ActivatableRef(id, null);
	return Util.createProxy(cl, clientRef, false);

	} catch (IllegalArgumentException e) {
	throw new StubNotFoundException(
	"class implements an illegal remote interface", e);

	} catch (ClassNotFoundException e) {
	throw new StubNotFoundException("unable to load class: " +
	className, e);
	} catch (MalformedURLException e) {
	throw new StubNotFoundException("malformed URL", e);
	}
	}

	/**
	* Invoke method on remote object. This method delegates remote
	* method invocation to the underlying ref type. If the
	* underlying reference is not known (is null), then the object
	* must be activated first. If an attempt at method invocation
	* fails, the object should force reactivation. Method invocation
	* must preserve "at most once" call semantics. In RMI, "at most
	* once" applies to parameter deserialization at the remote site
	* and the remote object's method execution. "At most once" does
	* not apply to parameter serialization at the client so the
	* parameters of a call don't need to be buffered in anticipation
	* of call retry. Thus, a method call is only be retried if the
	* initial method invocation does not execute at all at the server
	* (including parameter deserialization).
	*/
	public Object invoke(Remote obj,
	java.lang.reflect.Method method,
	Object[] params,
	long opnum)
	throws Exception
	{

	boolean force = false;
	RemoteRef localRef;
	Exception exception = null;

	/*
	* Attempt object activation if active ref is unknown.
	* Throws a RemoteException if object can't be activated.
	*/
	synchronized (this) {
	if (ref == null) {
	localRef = activate(force);
	force = true;
	} else {
	localRef = ref;
	}
	}

	for (int retries = MAX_RETRIES; retries > 0; retries--) {

	try {
	return localRef.invoke(obj, method, params, opnum);
	} catch (NoSuchObjectException e) {
	/*
	* Object is not active in VM; retry call
	*/
	exception = e;
	} catch (ConnectException e) {
	/*
	* Failure during connection setup; retry call
	*/
	exception = e;
	} catch (UnknownHostException e) {
	/*
	* Failure during connection setup; retry call.
	*/
	exception = e;
	} catch (ConnectIOException e) {
	/*
	* Failure setting up multiplexed connection or reusing
	* cached connection; retry call
	*/
	exception = e;
	} catch (MarshalException e) {
	/*
	* Failure during parameter serialization; call may
	* have reached server, so call retry not possible.
	*/
	throw e;
	} catch (ServerError e) {
	/*
	* Call reached server; propagate remote exception.
	*/
	throw e;
	} catch (ServerException e) {
	/*
	* Call reached server; propagate remote exception
	*/
	throw e;
	} catch (RemoteException e) {
	/*
	* This is a catch-all for other RemoteExceptions.
	* UnmarshalException being the only one relevant.
	*
	* StubNotFoundException should never show up because
	* it is generally thrown when attempting to locate
	* a stub.
	*
	* UnexpectedException should never show up because
	* it is only thrown by a stub and would be wrapped
	* in a ServerException if it was propagated by a
	* remote call.
	*/
	synchronized (this) {
	if (localRef == ref) {
	ref = null; // this may be overly conservative
	}
	}

	throw e;
	}

	if (retries > 1) {
	/*
	* Activate object, since object could not be reached.
	*/
	synchronized (this) {
	if (localRef.remoteEquals(ref) \|\| ref == null) {
	RemoteRef newRef = activate(force);

	if (newRef.remoteEquals(localRef) &&
	exception instanceof NoSuchObjectException &&
	force == false) {
	/*
	* If last exception was NoSuchObjectException,
	* then old value of ref is definitely wrong,
	* so make sure that it is different.
	*/
	newRef = activate(true);
	}

	localRef = newRef;
	force = true;
	} else {
	localRef = ref;
	force = false;
	}
	}
	}
	}

	/*
	* Retries unsuccessful, so throw last exception
	*/
	throw exception;
	}

	/**
	* private method to obtain the ref for a call.
	*/
	private synchronized RemoteRef getRef()
	throws RemoteException
	{
	if (ref == null) {
	ref = activate(false);
	}

	return ref;
	}

	/**
	* private method to activate the remote object.
	*
	* NOTE: the caller must be synchronized on "this" before
	* calling this method.
	*/
	private RemoteRef activate(boolean force)
	throws RemoteException
	{
	assert Thread.holdsLock(this);

	ref = null;
	try {
	/*
	* Activate the object and retrieve the remote reference
	* from inside the stub returned as the result. Then
	* set this activatable ref's internal ref to be the
	* ref inside the ref of the stub. In more clear terms,
	* the stub returned from the activate call contains an
	* ActivatableRef. We need to set the ref in this
	* ActivatableRef to the ref inside the ActivatableRef
	* retrieved from the stub. The ref type embedded in the
	* ActivatableRef is typically a UnicastRef.
	*/

	Remote proxy = id.activate(force);
	ActivatableRef newRef = null;

	if (proxy instanceof RemoteStub) {
	newRef = (ActivatableRef) ((RemoteStub) proxy).getRef();
	} else {
	/*
	* Assume that proxy is an instance of a dynamic proxy
	* class. If that assumption is not correct, or either of
	* the casts below fails, the resulting exception will be
	* wrapped in an ActivateFailedException below.
	*/
	RemoteObjectInvocationHandler handler =
	(RemoteObjectInvocationHandler)
	Proxy.getInvocationHandler(proxy);
	newRef = (ActivatableRef) handler.getRef();
	}
	ref = newRef.ref;
	return ref;

	} catch (ConnectException e) {
	throw new ConnectException("activation failed", e);
	} catch (RemoteException e) {
	throw new ConnectIOException("activation failed", e);
	} catch (UnknownObjectException e) {
	throw new NoSuchObjectException("object not registered");
	} catch (ActivationException e) {
	throw new ActivateFailedException("activation failed", e);
	}
	}

	/**
	* This call is used by the old 1.1 stub protocol and is
	* unsupported since activation requires 1.2 stubs.
	*/
	public synchronized RemoteCall newCall(RemoteObject obj,
	Operation[] ops,
	int opnum,
	long hash)
	throws RemoteException
	{
	throw new UnsupportedOperationException(versionComplaint);
	}

	/**
	* This call is used by the old 1.1 stub protocol and is
	* unsupported since activation requires 1.2 stubs.
	*/
	public void invoke(RemoteCall call) throws Exception
	{
	throw new UnsupportedOperationException(versionComplaint);
	}

	/**
	* This call is used by the old 1.1 stub protocol and is
	* unsupported since activation requires 1.2 stubs.
	*/
	public void done(RemoteCall call) throws RemoteException {
	throw new UnsupportedOperationException(versionComplaint);
	}

	/**
	* Returns the class of the ref type to be serialized
	*/
	public String getRefClass(ObjectOutput out)
	{
	return "ActivatableRef";
	}

	/**
	* Write out external representation for remote ref.
	*/
	public void writeExternal(ObjectOutput out) throws IOException
	{
	RemoteRef localRef = ref;

	out.writeObject(id);
	if (localRef == null) {
	out.writeUTF("");
	} else {
	out.writeUTF(localRef.getRefClass(out));
	localRef.writeExternal(out);
	}
	}

	/**
	* Read in external representation for remote ref.
	* @exception ClassNotFoundException If the class for an object
	* being restored cannot be found.
	*/
	public void readExternal(ObjectInput in)
	throws IOException, ClassNotFoundException
	{
	id = (ActivationID)in.readObject();
	ref = null;
	String className = in.readUTF();

	if (className.equals("")) return;

	try {
	Class<?> refClass = Class.forName(RemoteRef.packagePrefix + "." +
	className);
	ref = (RemoteRef)refClass.newInstance();
	ref.readExternal(in);
	} catch (InstantiationException e) {
	throw new UnmarshalException("Unable to create remote reference",
	e);
	} catch (IllegalAccessException e) {
	throw new UnmarshalException("Illegal access creating remote reference");
	}
	}

	//----------------------------------------------------------------------;
	/**
	* Method from object, forward from RemoteObject
	*/
	public String remoteToString() {
	return Util.getUnqualifiedName(getClass()) +
	" [remoteRef: " + ref + "]";
	}

	/**
	* default implementation of hashCode for remote objects
	*/
	public int remoteHashCode() {
	return id.hashCode();
	}

	/** default implementation of equals for remote objects
	*/
	public boolean remoteEquals(RemoteRef ref) {
	if (ref instanceof ActivatableRef)
	return id.equals(((ActivatableRef)ref).id);
	return false;
	}
	}

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