Java example source code file (UnicastRemoteObject.java)

This example Java source code file (UnicastRemoteObject.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

clonenotsupportedexception, deprecated, remoteexception, remoteserver, remotestub, rmi, rmiclientsocketfactory, rmiserversocketfactory, servercloneexception, unicastremoteobject, unicastserverref, unicastserverref2

The UnicastRemoteObject.java Java example source code

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

import java.rmi.*;
import sun.rmi.server.UnicastServerRef;
import sun.rmi.server.UnicastServerRef2;

/**
 * Used for exporting a remote object with JRMP and obtaining a stub
 * that communicates to the remote object. Stubs are either generated
 * at runtime using dynamic proxy objects, or they are generated statically
 * at build time, typically using the {@code rmic} tool.
 *
 * <p>Deprecated: Static Stubs. Support for statically
 * generated stubs is deprecated. This includes the API in this class that
 * requires the use of static stubs, as well as the runtime support for
 * loading static stubs.  Generating stubs dynamically is preferred, using one
 * of the five non-deprecated ways of exporting objects as listed below. Do
 * not run {@code rmic} to generate static stub classes. It is unnecessary, and
 * it is also deprecated.</em>
 *
 * <p>There are six ways to export remote objects:
 *
 * <ol>
 *
 * <li>Subclassing {@code UnicastRemoteObject} and calling the
 * {@link #UnicastRemoteObject()} constructor.
 *
 * <li>Subclassing {@code UnicastRemoteObject} and calling the
 * {@link #UnicastRemoteObject(int) UnicastRemoteObject(port)} constructor.
 *
 * <li>Subclassing {@code UnicastRemoteObject} and calling the
 * {@link #UnicastRemoteObject(int, RMIClientSocketFactory, RMIServerSocketFactory)
 * UnicastRemoteObject(port, csf, ssf)} constructor.
 *
 * <li>Calling the
 * {@link #exportObject(Remote) exportObject(Remote)} method.
 * <strong>Deprecated.
 *
 * <li>Calling the
 * {@link #exportObject(Remote, int) exportObject(Remote, port)} method.
 *
 * <li>Calling the
 * {@link #exportObject(Remote, int, RMIClientSocketFactory, RMIServerSocketFactory)
 * exportObject(Remote, port, csf, ssf)} method.
 *
 * </ol>
 *
 * <p>The fourth technique, {@link #exportObject(Remote)},
 * always uses statically generated stubs and is deprecated.
 *
 * <p>The other five techniques all use the following approach: if the
 * {@code java.rmi.server.ignoreStubClasses} property is {@code true}
 * (case insensitive) or if a static stub cannot be found, stubs are generated
 * dynamically using {@link java.lang.reflect.Proxy Proxy} objects. Otherwise,
 * static stubs are used.
 *
 * <p>The default value of the
 * {@code java.rmi.server.ignoreStubClasses} property is {@code false}.
 *
 * <p>Statically generated stubs are typically pregenerated from the
 * remote object's class using the {@code rmic} tool. A static stub is
 * loaded and an instance of that stub class is constructed as described
 * below.
 *
 * <ul>
 *
 * <li>A "root class" is determined as follows: if the remote object's
 * class directly implements an interface that extends {@link Remote}, then
 * the remote object's class is the root class; otherwise, the root class is
 * the most derived superclass of the remote object's class that directly
 * implements an interface that extends {@code Remote}.
 *
 * <li>The name of the stub class to load is determined by concatenating
 * the binary name of the root class with the suffix {@code _Stub}.
 *
 * <li>The stub class is loaded by name using the class loader of the root
 * class. The stub class must extend {@link RemoteStub} and must have a
 * public constructor that has one parameter of type {@link RemoteRef}.
 *
 * <li>Finally, an instance of the stub class is constructed with a
 * {@link RemoteRef}.
 *
 * <li>If the appropriate stub class could not be found, or if the stub class
 * could not be loaded, or if a problem occurs creating the stub instance, a
 * {@link StubNotFoundException} is thrown.
 *
 * </ul>
 *
 * <p>Stubs are dynamically generated by constructing an instance of
 * a {@link java.lang.reflect.Proxy Proxy} with the following characteristics:
 *
 * <ul>
 *
 * <li>The proxy's class is defined by the class loader of the remote
 * object's class.
 *
 * <li>The proxy implements all the remote interfaces implemented by the
 * remote object's class.
 *
 * <li>The proxy's invocation handler is a {@link
 * RemoteObjectInvocationHandler} instance constructed with a
 * {@link RemoteRef}.
 *
 * <li>If the proxy could not be created, a {@link StubNotFoundException}
 * will be thrown.
 *
 * </ul>
 *
 * @implNote
 * Depending upon which constructor or static method is used for exporting an
 * object, {@link RMISocketFactory} may be used for creating sockets.
 * By default, server sockets created by {@link RMISocketFactory}
 * listen on all network interfaces. See the
 * {@link RMISocketFactory} class and the section
 * <a href="{@docRoot}/../platform/rmi/spec/rmi-server29.html">RMI Socket Factories
 * in the
 * <a href="{@docRoot}/../platform/rmi/spec/rmiTOC.html">Java RMI Specification.
 *
 * @author  Ann Wollrath
 * @author  Peter Jones
 * @since   JDK1.1
 **/
public class UnicastRemoteObject extends RemoteServer {

    /**
     * @serial port number on which to export object
     */
    private int port = 0;

    /**
     * @serial client-side socket factory (if any)
     */
    private RMIClientSocketFactory csf = null;

    /**
     * @serial server-side socket factory (if any) to use when
     * exporting object
     */
    private RMIServerSocketFactory ssf = null;

    /* indicate compatibility with JDK 1.1.x version of class */
    private static final long serialVersionUID = 4974527148936298033L;

    /**
     * Creates and exports a new UnicastRemoteObject object using an
     * anonymous port.
     *
     * <p>The object is exported with a server socket
     * created using the {@link RMISocketFactory} class.
     *
     * @throws RemoteException if failed to export object
     * @since JDK1.1
     */
    protected UnicastRemoteObject() throws RemoteException
    {
        this(0);
    }

    /**
     * Creates and exports a new UnicastRemoteObject object using the
     * particular supplied port.
     *
     * <p>The object is exported with a server socket
     * created using the {@link RMISocketFactory} class.
     *
     * @param port the port number on which the remote object receives calls
     * (if <code>port is zero, an anonymous port is chosen)
     * @throws RemoteException if failed to export object
     * @since 1.2
     */
    protected UnicastRemoteObject(int port) throws RemoteException
    {
        this.port = port;
        exportObject((Remote) this, port);
    }

    /**
     * Creates and exports a new UnicastRemoteObject object using the
     * particular supplied port and socket factories.
     *
     * <p>Either socket factory may be {@code null}, in which case
     * the corresponding client or server socket creation method of
     * {@link RMISocketFactory} is used instead.
     *
     * @param port the port number on which the remote object receives calls
     * (if <code>port is zero, an anonymous port is chosen)
     * @param csf the client-side socket factory for making calls to the
     * remote object
     * @param ssf the server-side socket factory for receiving remote calls
     * @throws RemoteException if failed to export object
     * @since 1.2
     */
    protected UnicastRemoteObject(int port,
                                  RMIClientSocketFactory csf,
                                  RMIServerSocketFactory ssf)
        throws RemoteException
    {
        this.port = port;
        this.csf = csf;
        this.ssf = ssf;
        exportObject((Remote) this, port, csf, ssf);
    }

    /**
     * Re-export the remote object when it is deserialized.
     */
    private void readObject(java.io.ObjectInputStream in)
        throws java.io.IOException, java.lang.ClassNotFoundException
    {
        in.defaultReadObject();
        reexport();
    }

    /**
     * Returns a clone of the remote object that is distinct from
     * the original.
     *
     * @exception CloneNotSupportedException if clone failed due to
     * a RemoteException.
     * @return the new remote object
     * @since JDK1.1
     */
    public Object clone() throws CloneNotSupportedException
    {
        try {
            UnicastRemoteObject cloned = (UnicastRemoteObject) super.clone();
            cloned.reexport();
            return cloned;
        } catch (RemoteException e) {
            throw new ServerCloneException("Clone failed", e);
        }
    }

    /*
     * Exports this UnicastRemoteObject using its initialized fields because
     * its creation bypassed running its constructors (via deserialization
     * or cloning, for example).
     */
    private void reexport() throws RemoteException
    {
        if (csf == null && ssf == null) {
            exportObject((Remote) this, port);
        } else {
            exportObject((Remote) this, port, csf, ssf);
        }
    }

    /**
     * Exports the remote object to make it available to receive incoming
     * calls using an anonymous port. This method will always return a
     * statically generated stub.
     *
     * <p>The object is exported with a server socket
     * created using the {@link RMISocketFactory} class.
     *
     * @param obj the remote object to be exported
     * @return remote object stub
     * @exception RemoteException if export fails
     * @since JDK1.1
     * @deprecated This method is deprecated because it supports only static stubs.
     * Use {@link #exportObject(Remote, int) exportObject(Remote, port)} or
     * {@link #exportObject(Remote, int, RMIClientSocketFactory, RMIServerSocketFactory)
     * exportObject(Remote, port, csf, ssf)}
     * instead.
     */
    @Deprecated
    public static RemoteStub exportObject(Remote obj)
        throws RemoteException
    {
        /*
         * Use UnicastServerRef constructor passing the boolean value true
         * to indicate that only a generated stub class should be used.  A
         * generated stub class must be used instead of a dynamic proxy
         * because the return value of this method is RemoteStub which a
         * dynamic proxy class cannot extend.
         */
        return (RemoteStub) exportObject(obj, new UnicastServerRef(true));
    }

    /**
     * Exports the remote object to make it available to receive incoming
     * calls, using the particular supplied port.
     *
     * <p>The object is exported with a server socket
     * created using the {@link RMISocketFactory} class.
     *
     * @param obj the remote object to be exported
     * @param port the port to export the object on
     * @return remote object stub
     * @exception RemoteException if export fails
     * @since 1.2
     */
    public static Remote exportObject(Remote obj, int port)
        throws RemoteException
    {
        return exportObject(obj, new UnicastServerRef(port));
    }

    /**
     * Exports the remote object to make it available to receive incoming
     * calls, using a transport specified by the given socket factory.
     *
     * <p>Either socket factory may be {@code null}, in which case
     * the corresponding client or server socket creation method of
     * {@link RMISocketFactory} is used instead.
     *
     * @param obj the remote object to be exported
     * @param port the port to export the object on
     * @param csf the client-side socket factory for making calls to the
     * remote object
     * @param ssf the server-side socket factory for receiving remote calls
     * @return remote object stub
     * @exception RemoteException if export fails
     * @since 1.2
     */
    public static Remote exportObject(Remote obj, int port,
                                      RMIClientSocketFactory csf,
                                      RMIServerSocketFactory ssf)
        throws RemoteException
    {

        return exportObject(obj, new UnicastServerRef2(port, csf, ssf));
    }

    /**
     * Removes the remote object, obj, from the RMI runtime. If
     * successful, the object can no longer accept incoming RMI calls.
     * If the force parameter is true, the object is forcibly unexported
     * even if there are pending calls to the remote object or the
     * remote object still has calls in progress.  If the force
     * parameter is false, the object is only unexported if there are
     * no pending or in progress calls to the object.
     *
     * @param obj the remote object to be unexported
     * @param force if true, unexports the object even if there are
     * pending or in-progress calls; if false, only unexports the object
     * if there are no pending or in-progress calls
     * @return true if operation is successful, false otherwise
     * @exception NoSuchObjectException if the remote object is not
     * currently exported
     * @since 1.2
     */
    public static boolean unexportObject(Remote obj, boolean force)
        throws java.rmi.NoSuchObjectException
    {
        return sun.rmi.transport.ObjectTable.unexportObject(obj, force);
    }

    /**
     * Exports the specified object using the specified server ref.
     */
    private static Remote exportObject(Remote obj, UnicastServerRef sref)
        throws RemoteException
    {
        // if obj extends UnicastRemoteObject, set its ref.
        if (obj instanceof UnicastRemoteObject) {
            ((UnicastRemoteObject) obj).ref = sref;
        }
        return sref.exportObject(obj, null, false);
    }
}