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 * Copyright (c) 1996, 2004, 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.
 *
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package java.rmi.server;

import java.rmi.*;

/**
 * <code>RemoteRef</code> represents the handle for a remote object. A
 * <code>RemoteStub</code> uses a remote reference to carry out a
 * remote method invocation to a remote object.
 *
 * @author  Ann Wollrath
 * @since   1.1
 * @see     java.rmi.server.RemoteStub
 */
public interface RemoteRef extends java.io.Externalizable {

    /** indicate compatibility with JDK 1.1.x version of class. */
    static final long serialVersionUID = 3632638527362204081L;

    /**
     * Initialize the server package prefix: assumes that the
     * implementation of server ref classes (e.g., UnicastRef,
     * UnicastServerRef) are located in the package defined by the
     * prefix.
     */
    final static String packagePrefix = "sun.rmi.server";

    /**
     * Invoke a method. This form of delegating method invocation
     * to the reference allows the reference to take care of
     * setting up the connection to the remote host, marshaling
     * some representation for the method and parameters, then
     * communicating the method invocation to the remote host.
     * This method either returns the result of a method invocation
     * on the remote object which resides on the remote host or
     * throws a RemoteException if the call failed or an
     * application-level exception if the remote invocation throws
     * an exception.
     *
     * @param obj the object that contains the RemoteRef (e.g., the
     *            RemoteStub for the object.
     * @param method the method to be invoked
     * @param params the parameter list
     * @param opnum  a hash that may be used to represent the method
     * @return result of remote method invocation
     * @exception Exception if any exception occurs during remote method
     * invocation
     * @since 1.2
     */
    Object invoke(Remote obj,
                  java.lang.reflect.Method method,
                  Object[] params,
                  long opnum)
        throws Exception;

    /**
     * Creates an appropriate call object for a new remote method
     * invocation on this object.  Passing operation array and index,
     * allows the stubs generator to assign the operation indexes and
     * interpret them. The remote reference may need the operation to
     * encode in the call.
     *
     * @since 1.1
     * @deprecated 1.2 style stubs no longer use this method. Instead of
     * using a sequence of method calls on the stub's the remote reference
     * (<code>newCall</code>, <code>invoke</code>, and <code>done</code>), a
     * stub uses a single method, <code>invoke(Remote, Method, Object[],
     * int)</code>, on the remote reference to carry out parameter
     * marshalling, remote method executing and unmarshalling of the return
     * value.
     *
     * @param obj remote stub through which to make call
     * @param op array of stub operations
     * @param opnum operation number
     * @param hash stub/skeleton interface hash
     * @return call object representing remote call
     * @throws RemoteException if failed to initiate new remote call
     * @see #invoke(Remote,java.lang.reflect.Method,Object[],long)
     */
    @Deprecated
    RemoteCall newCall(RemoteObject obj, Operation[] op, int opnum, long hash)
        throws RemoteException;

    /**
     * Executes the remote call.
     *
     * Invoke will raise any "user" exceptions which
     * should pass through and not be caught by the stub.  If any
     * exception is raised during the remote invocation, invoke should
     * take care of cleaning up the connection before raising the
     * "user" or remote exception.
     *
     * @since 1.1
     * @deprecated 1.2 style stubs no longer use this method. Instead of
     * using a sequence of method calls to the remote reference
     * (<code>newCall</code>, <code>invoke</code>, and <code>done</code>), a
     * stub uses a single method, <code>invoke(Remote, Method, Object[],
     * int)</code>, on the remote reference to carry out parameter
     * marshalling, remote method executing and unmarshalling of the return
     * value.
     *
     * @param call object representing remote call
     * @throws Exception if any exception occurs during remote method
     * @see #invoke(Remote,java.lang.reflect.Method,Object[],long)
     */
    @Deprecated
    void invoke(RemoteCall call) throws Exception;

    /**
     * Allows the remote reference to clean up (or reuse) the connection.
     * Done should only be called if the invoke returns successfully
     * (non-exceptionally) to the stub.
     *
     * @since 1.1
     * @deprecated 1.2 style stubs no longer use this method. Instead of
     * using a sequence of method calls to the remote reference
     * (<code>newCall</code>, <code>invoke</code>, and <code>done</code>), a
     * stub uses a single method, <code>invoke(Remote, Method, Object[],
     * int)</code>, on the remote reference to carry out parameter
     * marshalling, remote method executing and unmarshalling of the return
     * value.
     *
     * @param call object representing remote call
     * @throws RemoteException if remote error occurs during call cleanup
     * @see #invoke(Remote,java.lang.reflect.Method,Object[],long)
     */
    @Deprecated
    void done(RemoteCall call) throws RemoteException;

    /**
     * Returns the class name of the ref type to be serialized onto
     * the stream 'out'.
     * @param out the output stream to which the reference will be serialized
     * @return the class name (without package qualification) of the reference
     * type
     * @since 1.1
     */
    String getRefClass(java.io.ObjectOutput out);

    /**
     * Returns a hashcode for a remote object.  Two remote object stubs
     * that refer to the same remote object will have the same hash code
     * (in order to support remote objects as keys in hash tables).
     *
     * @return remote object hashcode
     * @see             java.util.Hashtable
     * @since 1.1
     */
    int remoteHashCode();

    /**
     * Compares two remote objects for equality.
     * Returns a boolean that indicates whether this remote object is
     * equivalent to the specified Object. This method is used when a
     * remote object is stored in a hashtable.
     * @param   obj     the Object to compare with
     * @return  true if these Objects are equal; false otherwise.
     * @see             java.util.Hashtable
     * @since 1.1
     */
    boolean remoteEquals(RemoteRef obj);

    /**
     * Returns a String that represents the reference of this remote
     * object.
     * @return string representing remote object reference
     * @since 1.1
     */
    String remoteToString();

}
