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 * 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).
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 * 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,
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 *
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package sun.rmi.server;

import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputFilter;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.rmi.AccessException;
import java.rmi.MarshalException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.ServerError;
import java.rmi.ServerException;
import java.rmi.UnmarshalException;
import java.rmi.server.ExportException;
import java.rmi.server.Operation;
import java.rmi.server.RemoteCall;
import java.rmi.server.RemoteRef;
import java.rmi.server.RemoteStub;
import java.rmi.server.ServerNotActiveException;
import java.rmi.server.ServerRef;
import java.rmi.server.Skeleton;
import java.rmi.server.SkeletonNotFoundException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import sun.rmi.runtime.Log;
import sun.rmi.transport.LiveRef;
import sun.rmi.transport.StreamRemoteCall;
import sun.rmi.transport.Target;
import sun.rmi.transport.tcp.TCPTransport;

UnicastServerRef implements the remote reference layer server-side behavior for remote objects exported with the "UnicastRef" reference type. If an ObjectInputFilter is supplied it is invoked during deserialization to filter the arguments, otherwise the default filter of ObjectInputStream applies. 
Author:
 Ann Wollrath,  Roger Riggs,  Peter Jones/**
 * UnicastServerRef implements the remote reference layer server-side
 * behavior for remote objects exported with the "UnicastRef" reference
 * type.
 * If an {@link ObjectInputFilter ObjectInputFilter} is supplied it is
 * invoked during deserialization to filter the arguments,
 * otherwise the default filter of {@link ObjectInputStream ObjectInputStream}
 * applies.
 *
 * @author  Ann Wollrath
 * @author  Roger Riggs
 * @author  Peter Jones
 */
@SuppressWarnings("deprecation")
public class UnicastServerRef extends UnicastRef
    implements ServerRef, Dispatcher
{
    
value of server call log property /** value of server call log property */
    public static final boolean logCalls = AccessController.doPrivileged(
        (PrivilegedAction<Boolean>) () -> Boolean.getBoolean("java.rmi.server.logCalls"));

    
server call log /** server call log */
    public static final Log callLog =
        Log.getLog("sun.rmi.server.call", "RMI", logCalls);

    // use serialVersionUID from JDK 1.2.2 for interoperability
    private static final long serialVersionUID = -7384275867073752268L;

    
flag to enable writing exceptions to System.err /** flag to enable writing exceptions to System.err */
    private static final boolean wantExceptionLog =
        AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->
            Boolean.getBoolean("sun.rmi.server.exceptionTrace"));

    private boolean forceStubUse = false;

    
flag to remove server-side stack traces before marshalling
exceptions thrown by remote invocations to this VM
/**
     * flag to remove server-side stack traces before marshalling
     * exceptions thrown by remote invocations to this VM
     */
    private static final boolean suppressStackTraces =
        AccessController.doPrivileged((PrivilegedAction<Boolean>) () ->
            Boolean.getBoolean("sun.rmi.server.suppressStackTraces"));

    
skeleton to dispatch remote calls through, for 1.1 stub protocol
(may be null if stub class only uses 1.2 stub protocol)
/**
     * skeleton to dispatch remote calls through, for 1.1 stub protocol
     * (may be null if stub class only uses 1.2 stub protocol)
     */
    private transient Skeleton skel;

    // The ObjectInputFilter for checking the invocation arguments
    private final transient ObjectInputFilter filter;

    
maps method hash to Method object for each remote method /** maps method hash to Method object for each remote method */
    private transient Map<Long,Method> hashToMethod_Map = null;

    
A weak hash map, mapping classes to hash maps that map method
hashes to method objects.
/**
     * A weak hash map, mapping classes to hash maps that map method
     * hashes to method objects.
     **/
    private static final WeakClassHashMap<Map<Long,Method>> hashToMethod_Maps =
        new HashToMethod_Maps();

    
cache of impl classes that have no corresponding skeleton class /** cache of impl classes that have no corresponding skeleton class */
    private static final Map<Class<?>,?> withoutSkeletons =
        Collections.synchronizedMap(new WeakHashMap<Class<?>,Void>());

    private final AtomicInteger methodCallIDCount = new AtomicInteger(0);

    
Create a new (empty) Unicast server remote reference.
The filter is null to defer to the  default ObjectInputStream filter, if any.
/**
     * Create a new (empty) Unicast server remote reference.
     * The filter is null to defer to the  default ObjectInputStream filter, if any.
     */
    public UnicastServerRef() {
        this.filter = null;
    }

    
Construct a Unicast server remote reference for a specified
liveRef.
The filter is null to defer to the  default ObjectInputStream filter, if any.
/**
     * Construct a Unicast server remote reference for a specified
     * liveRef.
     * The filter is null to defer to the  default ObjectInputStream filter, if any.
     */
    public UnicastServerRef(LiveRef ref) {
        super(ref);
        this.filter = null;
    }

    
Construct a Unicast server remote reference for a specified
liveRef and filter.
/**
     * Construct a Unicast server remote reference for a specified
     * liveRef and filter.
     */
    public UnicastServerRef(LiveRef ref, ObjectInputFilter filter) {
        super(ref);
        this.filter = filter;
    }

    
Construct a Unicast server remote reference to be exported
on the specified port.
/**
     * Construct a Unicast server remote reference to be exported
     * on the specified port.
     */
    public UnicastServerRef(int port) {
        super(new LiveRef(port));
        this.filter = null;
    }

    
Constructs a UnicastServerRef to be exported on an
anonymous port (i.e., 0) and that uses a pregenerated stub class
(NOT a dynamic proxy instance) if 'forceStubUse' is 'true'.
This constructor is only called by the method
UnicastRemoteObject.exportObject(Remote) passing 'true' for
'forceStubUse'.  The UnicastRemoteObject.exportObject(Remote) method
returns RemoteStub, so it must ensure that the stub for the
exported object is an instance of a pregenerated stub class that
extends RemoteStub (instead of an instance of a dynamic proxy class
which is not an instance of RemoteStub).
/**
     * Constructs a UnicastServerRef to be exported on an
     * anonymous port (i.e., 0) and that uses a pregenerated stub class
     * (NOT a dynamic proxy instance) if 'forceStubUse' is 'true'.
     *
     * This constructor is only called by the method
     * UnicastRemoteObject.exportObject(Remote) passing 'true' for
     * 'forceStubUse'.  The UnicastRemoteObject.exportObject(Remote) method
     * returns RemoteStub, so it must ensure that the stub for the
     * exported object is an instance of a pregenerated stub class that
     * extends RemoteStub (instead of an instance of a dynamic proxy class
     * which is not an instance of RemoteStub).
     **/
    public UnicastServerRef(boolean forceStubUse) {
        this(0);
        this.forceStubUse = forceStubUse;
    }

    
With the addition of support for dynamic proxies as stubs, this
method is obsolete because it returns RemoteStub instead of the more
general Remote.  It should not be called.  It sets the
'forceStubUse' flag to true so that the stub for the exported object
is forced to be an instance of the pregenerated stub class, which
extends RemoteStub.
Export this object, create the skeleton and stubs for this
dispatcher.  Create a stub based on the type of the impl,
initialize it with the appropriate remote reference. Create the
target defined by the impl, dispatcher (this) and stub.
Export that target via the Ref.
/**
     * With the addition of support for dynamic proxies as stubs, this
     * method is obsolete because it returns RemoteStub instead of the more
     * general Remote.  It should not be called.  It sets the
     * 'forceStubUse' flag to true so that the stub for the exported object
     * is forced to be an instance of the pregenerated stub class, which
     * extends RemoteStub.
     *
     * Export this object, create the skeleton and stubs for this
     * dispatcher.  Create a stub based on the type of the impl,
     * initialize it with the appropriate remote reference. Create the
     * target defined by the impl, dispatcher (this) and stub.
     * Export that target via the Ref.
     **/
    public RemoteStub exportObject(Remote impl, Object data)
        throws RemoteException
    {
        forceStubUse = true;
        return (RemoteStub) exportObject(impl, data, false);
    }

    
Export this object, create the skeleton and stubs for this
dispatcher.  Create a stub based on the type of the impl,
initialize it with the appropriate remote reference. Create the
target defined by the impl, dispatcher (this) and stub.
Export that target via the Ref.
/**
     * Export this object, create the skeleton and stubs for this
     * dispatcher.  Create a stub based on the type of the impl,
     * initialize it with the appropriate remote reference. Create the
     * target defined by the impl, dispatcher (this) and stub.
     * Export that target via the Ref.
     */
    public Remote exportObject(Remote impl, Object data,
                               boolean permanent)
        throws RemoteException
    {
        Class<?> implClass = impl.getClass();
        Remote stub;

        try {
            stub = Util.createProxy(implClass, getClientRef(), forceStubUse);
        } catch (IllegalArgumentException e) {
            throw new ExportException(
                "remote object implements illegal remote interface", e);
        }
        if (stub instanceof RemoteStub) {
            setSkeleton(impl);
        }

        Target target =
            new Target(impl, this, stub, ref.getObjID(), permanent);
        ref.exportObject(target);
        hashToMethod_Map = hashToMethod_Maps.get(implClass);
        return stub;
    }

    
Return the hostname of the current client.  When called from a
thread actively handling a remote method invocation the
hostname of the client is returned.
Throws:
ServerNotActiveException – If called outside of servicing
a remote method invocation./**
     * Return the hostname of the current client.  When called from a
     * thread actively handling a remote method invocation the
     * hostname of the client is returned.
     * @exception ServerNotActiveException If called outside of servicing
     * a remote method invocation.
     */
    public String getClientHost() throws ServerNotActiveException {
        return TCPTransport.getClientHost();
    }

    
Discovers and sets the appropriate skeleton for the impl.
/**
     * Discovers and sets the appropriate skeleton for the impl.
     */
    public void setSkeleton(Remote impl) throws RemoteException {
        if (!withoutSkeletons.containsKey(impl.getClass())) {
            try {
                skel = Util.createSkeleton(impl);
            } catch (SkeletonNotFoundException e) {
                /*
                 * Ignore exception for skeleton class not found, because a
                 * skeleton class is not necessary with the 1.2 stub protocol.
                 * Remember that this impl's class does not have a skeleton
                 * class so we don't waste time searching for it again.
                 */
                withoutSkeletons.put(impl.getClass(), null);
            }
        }
    }

    
Call to dispatch to the remote object (on the server side).
The up-call to the server and the marshalling of return result
(or exception) should be handled before returning from this
method.
Params:
obj – the target remote object for the call
call – the "remote call" from which operation and
method arguments can be obtained.
Throws:
IOException – If unable to marshal return result or
release input or output streams/**
     * Call to dispatch to the remote object (on the server side).
     * The up-call to the server and the marshalling of return result
     * (or exception) should be handled before returning from this
     * method.
     * @param obj the target remote object for the call
     * @param call the "remote call" from which operation and
     * method arguments can be obtained.
     * @exception IOException If unable to marshal return result or
     * release input or output streams
     */
    public void dispatch(Remote obj, RemoteCall call) throws IOException {
        // positive operation number in 1.1 stubs;
        // negative version number in 1.2 stubs and beyond...
        int num;
        long op;

        try {
            // read remote call header
            ObjectInput in;
            try {
                in = call.getInputStream();
                num = in.readInt();
            } catch (Exception readEx) {
                throw new UnmarshalException("error unmarshalling call header",
                                             readEx);
            }
            if (skel != null) {
                // If there is a skeleton, use it
                    oldDispatch(obj, call, num);
                    return;

            } else if (num >= 0){
                throw new UnmarshalException(
                        "skeleton class not found but required for client version");
            }
            try {
                op = in.readLong();
            } catch (Exception readEx) {
                throw new UnmarshalException("error unmarshalling call header",
                        readEx);
            }

            /*
             * Since only system classes (with null class loaders) will be on
             * the execution stack during parameter unmarshalling for the 1.2
             * stub protocol, tell the MarshalInputStream not to bother trying
             * to resolve classes using its superclasses's default method of
             * consulting the first non-null class loader on the stack.
             */
            MarshalInputStream marshalStream = (MarshalInputStream) in;
            marshalStream.skipDefaultResolveClass();

            Method method = hashToMethod_Map.get(op);
            if (method == null) {
                throw new UnmarshalException("unrecognized method hash: " +
                    "method not supported by remote object");
            }

            // if calls are being logged, write out object id and operation
            logCall(obj, method);

            // unmarshal parameters
            Class<?>[] types = method.getParameterTypes();
            Object[] params = new Object[types.length];

            try {
                unmarshalCustomCallData(in);
                // Unmarshal the parameters
                for (int i = 0; i < types.length; i++) {
                    params[i] = unmarshalValue(types[i], in);
                }

            } catch (AccessException aex) {
                // For compatibility, AccessException is not wrapped in UnmarshalException
                // disable saving any refs in the inputStream for GC
                ((StreamRemoteCall) call).discardPendingRefs();
                throw aex;
            } catch (java.io.IOException | ClassNotFoundException e) {
                // disable saving any refs in the inputStream for GC
                ((StreamRemoteCall) call).discardPendingRefs();
                throw new UnmarshalException(
                    "error unmarshalling arguments", e);
            } finally {
                call.releaseInputStream();
            }

            // make upcall on remote object
            Object result;
            try {
                result = method.invoke(obj, params);
            } catch (InvocationTargetException e) {
                throw e.getTargetException();
            }

            // marshal return value
            try {
                ObjectOutput out = call.getResultStream(true);
                Class<?> rtype = method.getReturnType();
                if (rtype != void.class) {
                    marshalValue(rtype, result, out);
                }
            } catch (IOException ex) {
                throw new MarshalException("error marshalling return", ex);
                /*
                 * This throw is problematic because when it is caught below,
                 * we attempt to marshal it back to the client, but at this
                 * point, a "normal return" has already been indicated,
                 * so marshalling an exception will corrupt the stream.
                 * This was the case with skeletons as well; there is no
                 * immediately obvious solution without a protocol change.
                 */
            }
        } catch (Throwable e) {
            Throwable origEx = e;
            logCallException(e);

            ObjectOutput out = call.getResultStream(false);
            if (e instanceof Error) {
                e = new ServerError(
                    "Error occurred in server thread", (Error) e);
            } else if (e instanceof RemoteException) {
                e = new ServerException(
                    "RemoteException occurred in server thread",
                    (Exception) e);
            }
            if (suppressStackTraces) {
                clearStackTraces(e);
            }
            out.writeObject(e);

            // AccessExceptions should cause Transport.serviceCall
            // to flag the connection as unusable.
            if (origEx instanceof AccessException) {
                throw new IOException("Connection is not reusable", origEx);
            }
        } finally {
            call.releaseInputStream(); // in case skeleton doesn't
            call.releaseOutputStream();
        }
    }

    
Sets a filter for invocation arguments, if a filter has been set.
Called by dispatch before the arguments are read.
/**
     * Sets a filter for invocation arguments, if a filter has been set.
     * Called by dispatch before the arguments are read.
     */
    protected void unmarshalCustomCallData(ObjectInput in)
            throws IOException, ClassNotFoundException {
        if (filter != null &&
                in instanceof ObjectInputStream) {
            // Set the filter on the stream
            ObjectInputStream ois = (ObjectInputStream) in;

            AccessController.doPrivileged((PrivilegedAction<Void>)() -> {
                ois.setObjectInputFilter(filter);
                return null;
            });
        }
    }

    
Handle server-side dispatch using the RMI 1.1 stub/skeleton
protocol, given a non-negative operation number or negative method hash
that has already been read from the call stream.
Exceptions are handled by the caller to be sent to the remote client.
Params:
obj – the target remote object for the call
call – the "remote call" from which operation and
method arguments can be obtained.
op – the operation number
Throws:
Exception – if unable to marshal return result or
release input or output streams/**
     * Handle server-side dispatch using the RMI 1.1 stub/skeleton
     * protocol, given a non-negative operation number or negative method hash
     * that has already been read from the call stream.
     * Exceptions are handled by the caller to be sent to the remote client.
     *
     * @param obj the target remote object for the call
     * @param call the "remote call" from which operation and
     * method arguments can be obtained.
     * @param op the operation number
     * @throws Exception if unable to marshal return result or
     * release input or output streams
     */
    private void oldDispatch(Remote obj, RemoteCall call, int op)
        throws Exception
    {
        long hash;              // hash for matching stub with skeleton

        // read remote call header
        ObjectInput in;
        in = call.getInputStream();
        try {
            Class<?> clazz = Class.forName("sun.rmi.transport.DGCImpl_Skel");
            if (clazz.isAssignableFrom(skel.getClass())) {
                ((MarshalInputStream)in).useCodebaseOnly();
            }
        } catch (ClassNotFoundException ignore) { }

        try {
            hash = in.readLong();
        } catch (Exception ioe) {
            throw new UnmarshalException("error unmarshalling call header", ioe);
        }

        // if calls are being logged, write out object id and operation
        Operation[] operations = skel.getOperations();
        logCall(obj, op >= 0 && op < operations.length ?  operations[op] : "op: " + op);
        unmarshalCustomCallData(in);
        // dispatch to skeleton for remote object
        skel.dispatch(obj, call, op, hash);
    }

    
Clear the stack trace of the given Throwable by replacing it with
an empty StackTraceElement array, and do the same for all of its
chained causative exceptions.
/**
     * Clear the stack trace of the given Throwable by replacing it with
     * an empty StackTraceElement array, and do the same for all of its
     * chained causative exceptions.
     */
    public static void clearStackTraces(Throwable t) {
        StackTraceElement[] empty = new StackTraceElement[0];
        while (t != null) {
            t.setStackTrace(empty);
            t = t.getCause();
        }
    }

    
Log the details of an incoming call.  The method parameter is either of
type java.lang.reflect.Method or java.rmi.server.Operation.
/**
     * Log the details of an incoming call.  The method parameter is either of
     * type java.lang.reflect.Method or java.rmi.server.Operation.
     */
    private void logCall(Remote obj, Object method) {
        if (callLog.isLoggable(Log.VERBOSE)) {
            String clientHost;
            try {
                clientHost = getClientHost();
            } catch (ServerNotActiveException snae) {
                clientHost = "(local)"; // shouldn't happen
            }
            callLog.log(Log.VERBOSE, "[" + clientHost + ": " +
                              obj.getClass().getName() +
                              ref.getObjID().toString() + ": " +
                              method + "]");
        }
    }

    
Log the exception detail of an incoming call.
/**
     * Log the exception detail of an incoming call.
     */
    private void logCallException(Throwable e) {
        // if calls are being logged, log them
        if (callLog.isLoggable(Log.BRIEF)) {
            String clientHost = "";
            try {
                clientHost = "[" + getClientHost() + "] ";
            } catch (ServerNotActiveException snae) {
            }
            callLog.log(Log.BRIEF, clientHost + "exception: ", e);
        }

        // write exceptions (only) to System.err if desired
        if (wantExceptionLog) {
            java.io.PrintStream log = System.err;
            synchronized (log) {
                log.println();
                log.println("Exception dispatching call to " +
                            ref.getObjID() + " in thread \"" +
                            Thread.currentThread().getName() +
                            "\" at " + (new Date()) + ":");
                e.printStackTrace(log);
            }
        }
    }

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

    
Return the client remote reference for this remoteRef.
In the case of a client RemoteRef "this" is the answer.
For a server remote reference, a client side one will have to
found or created.
/**
     * Return the client remote reference for this remoteRef.
     * In the case of a client RemoteRef "this" is the answer.
     * For a server remote reference, a client side one will have to
     * found or created.
     */
    protected RemoteRef getClientRef() {
        return new UnicastRef(ref);
    }

    
Write out external representation for remote ref.
/**
     * Write out external representation for remote ref.
     */
    public void writeExternal(ObjectOutput out) throws IOException {
    }

    
Read in external representation for remote ref.
Throws:
ClassNotFoundException – If the class for an object
being restored cannot be found./**
     * 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
    {
        // object is re-exported elsewhere (e.g., by UnicastRemoteObject)
        ref = null;
        skel = null;
    }


    
A weak hash map, mapping classes to hash maps that map method
hashes to method objects.
/**
     * A weak hash map, mapping classes to hash maps that map method
     * hashes to method objects.
     **/
    private static class HashToMethod_Maps
        extends WeakClassHashMap<Map<Long,Method>>
    {
        HashToMethod_Maps() {}

        protected Map<Long,Method> computeValue(Class<?> remoteClass) {
            Map<Long,Method> map = new HashMap<>();
            for (Class<?> cl = remoteClass;
                 cl != null;
                 cl = cl.getSuperclass())
            {
                for (Class<?> intf : cl.getInterfaces()) {
                    if (Remote.class.isAssignableFrom(intf)) {
                        for (Method method : intf.getMethods()) {
                            final Method m = method;
                            /*
                             * Set this Method object to override language
                             * access checks so that the dispatcher can invoke
                             * methods from non-public remote interfaces.
                             */
                            AccessController.doPrivileged(
                                new PrivilegedAction<Void>() {
                                public Void run() {
                                    m.setAccessible(true);
                                    return null;
                                }
                            });
                            map.put(Util.computeMethodHash(m), m);
                        }
                    }
                }
            }
            return map;
        }
    }

}