Activatable.java

/*
 * Copyright 1997-2005 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
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package java.rmi.activation;

import java.rmi.MarshalledObject;
import java.rmi.NoSuchObjectException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.activation.UnknownGroupException;
import java.rmi.activation.UnknownObjectException;
import java.rmi.server.RMIClientSocketFactory;
import java.rmi.server.RMIServerSocketFactory;
import java.rmi.server.RemoteServer;
import sun.rmi.server.ActivatableServerRef;

/**
 * The <code>Activatable</code> class provides support for remote
 * objects that require persistent access over time and that
 * can be activated by the system.
 *
 * <p>For the constructors and static <code>exportObject</code> methods,
 * the stub for a remote object being exported is obtained as described in
 * {@link java.rmi.server.UnicastRemoteObject}.
 *
 * <p>An attempt to serialize explicitly an instance of this class will
 * fail.
 *
 * @author      Ann Wollrath
 * @since       1.2
 * @serial      exclude
 */
public abstract class Activatable extends RemoteServer {

    private ActivationID id;
    /** indicate compatibility with the Java 2 SDK v1.2 version of class */
    private static final long serialVersionUID = -3120617863591563455L;

    /**
     * Constructs an activatable remote object by registering
     * an activation descriptor (with the specified location, data, and
     * restart mode) for this object, and exporting the object with the
     * specified port.
     *
     * <p><strong>Note:</strong> Using the <code>Activatable</code>
     * constructors that both register and export an activatable remote
     * object is strongly discouraged because the actions of registering
     * and exporting the remote object are <i>not</i> guaranteed to be
     * atomic.  Instead, an application should register an activation
     * descriptor and export a remote object separately, so that exceptions
     * can be handled properly.
     *
     * <p>This method invokes the {@link
     * #exportObject(Remote,String,MarshalledObject,boolean,int)
     * exportObject} method with this object, and the specified location,
     * data, restart mode, and port.  Subsequent calls to {@link #getID}
     * will return the activation identifier returned from the call to
     * <code>exportObject</code>.
     *
     * @param location the location for classes for this object
     * @param data the object's initialization data
     * @param port the port on which the object is exported (an anonymous
     * port is used if port=0)
     * @param restart if true, the object is restarted (reactivated) when
     * either the activator is restarted or the object's activation group
     * is restarted after an unexpected crash; if false, the object is only
     * activated on demand.  Specifying <code>restart</code> to be
     * <code>true</code> does not force an initial immediate activation of
     * a newly registered object;  initial activation is lazy.
     * @exception ActivationException if object registration fails.
     * @exception RemoteException if either of the following fails:
     * a) registering the object with the activation system or b) exporting
     * the object to the RMI runtime.
     * @since 1.2
     **/
    protected Activatable(String location,
                          MarshalledObject<?> data,
                          boolean restart,
                          int port)
        throws ActivationException, RemoteException
    {
        super();
        id = exportObject(this, location, data, restart, port);
    }

    /**
     * Constructs an activatable remote object by registering
     * an activation descriptor (with the specified location, data, and
     * restart mode) for this object, and exporting the object with the
     * specified port, and specified client and server socket factories.
     *
     * <p><strong>Note:</strong> Using the <code>Activatable</code>
     * constructors that both register and export an activatable remote
     * object is strongly discouraged because the actions of registering
     * and exporting the remote object are <i>not</i> guaranteed to be
     * atomic.  Instead, an application should register an activation
     * descriptor and export a remote object separately, so that exceptions
     * can be handled properly.
     *
     * <p>This method invokes the {@link
     * #exportObject(Remote,String,MarshalledObject,boolean,int,RMIClientSocketFactory,RMIServerSocketFactory)
     * exportObject} method with this object, and the specified location,
     * data, restart mode, port, and client and server socket factories.
     * Subsequent calls to {@link #getID} will return the activation
     * identifier returned from the call to <code>exportObject</code>.
     *
     * @param location the location for classes for this object
     * @param data the object's initialization data
     * @param restart if true, the object is restarted (reactivated) when
     * either the activator is restarted or the object's activation group
     * is restarted after an unexpected crash; if false, the object is only
     * activated on demand.  Specifying <code>restart</code> to be
     * <code>true</code> does not force an initial immediate activation of
     * a newly registered object;  initial activation is lazy.
     * @param port the port on which the object is exported (an anonymous
     * port is used if port=0)
     * @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
     * @exception ActivationException if object registration fails.
     * @exception RemoteException if either of the following fails:
     * a) registering the object with the activation system or b) exporting
     * the object to the RMI runtime.
     * @since 1.2
     **/
    protected Activatable(String location,
                          MarshalledObject<?> data,
                          boolean restart,
                          int port,
                          RMIClientSocketFactory csf,
                          RMIServerSocketFactory ssf)
        throws ActivationException, RemoteException
    {
        super();
        id = exportObject(this, location, data, restart, port, csf, ssf);
    }

    /**
     * Constructor used to activate/export the object on a specified
     * port. An "activatable" remote object must have a constructor that
     * takes two arguments: <ul>
     * <li>the object's activation identifier (<code>ActivationID</code>), and
     * <li>the object's initialization data (a <code>MarshalledObject</code>).
     * </ul><p>
     *
     * A concrete subclass of this class must call this constructor when it is
     * <i>activated</i> via the two parameter constructor described above. As
     * a side-effect of construction, the remote object is "exported"
     * to the RMI runtime (on the specified <code>port</code>) and is
     * available to accept incoming calls from clients.
     *
     * @param id activation identifier for the object
     * @param port the port number on which the object is exported
     * @exception RemoteException if exporting the object to the RMI
     * runtime fails
     * @since 1.2
     */
    protected Activatable(ActivationID id, int port)
        throws RemoteException
    {
        super();
        this.id = id;
        exportObject(this, id, port);
    }

    /**
     * Constructor used to activate/export the object on a specified
     * port. An "activatable" remote object must have a constructor that
     * takes two arguments: <ul>
     * <li>the object's activation identifier (<code>ActivationID</code>), and
     * <li>the object's initialization data (a <code>MarshalledObject</code>).
     * </ul><p>
     *
     * A concrete subclass of this class must call this constructor when it is
     * <i>activated</i> via the two parameter constructor described above. As
     * a side-effect of construction, the remote object is "exported"
     * to the RMI runtime (on the specified <code>port</code>) and is
     * available to accept incoming calls from clients.
     *
     * @param id activation identifier for the object
     * @param port the port number on which the object is exported
     * @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
     * @exception RemoteException if exporting the object to the RMI
     * runtime fails
     * @since 1.2
     */
    protected Activatable(ActivationID id, int port,
                          RMIClientSocketFactory csf,
                          RMIServerSocketFactory ssf)
        throws RemoteException
    {
        super();
        this.id = id;
        exportObject(this, id, port, csf, ssf);
    }

    /**
     * Returns the object's activation identifier.  The method is
     * protected so that only subclasses can obtain an object's
     * identifier.
     * @return the object's activation identifier
     * @since 1.2
     */
    protected ActivationID getID() {
        return id;
    }

    /**
     * Register an object descriptor for an activatable remote
     * object so that is can be activated on demand.
     *
     * @param desc  the object's descriptor
     * @return the stub for the activatable remote object
     * @exception UnknownGroupException if group id in <code>desc</code>
     * is not registered with the activation system
     * @exception ActivationException if activation system is not running
     * @exception RemoteException if remote call fails
     * @since 1.2
     */
    public static Remote register(ActivationDesc desc)
        throws UnknownGroupException, ActivationException, RemoteException
    {
        // register object with activator.
        ActivationID id =
            ActivationGroup.getSystem().registerObject(desc);
        return sun.rmi.server.ActivatableRef.getStub(desc, id);
    }

    /**
     * Informs the system that the object with the corresponding activation
     * <code>id</code> is currently inactive. If the object is currently
     * active, the object is "unexported" from the RMI runtime (only if
     * there are no pending or in-progress calls)
     * so the that it can no longer receive incoming calls. This call
     * informs this VM's ActivationGroup that the object is inactive,
     * that, in turn, informs its ActivationMonitor. If this call
     * completes successfully, a subsequent activate request to the activator
     * will cause the object to reactivate. The operation may still
     * succeed if the object is considered active but has already
     * unexported itself.
     *
     * @param id the object's activation identifier
     * @return true if the operation succeeds (the operation will
     * succeed if the object in currently known to be active and is
     * either already unexported or is currently exported and has no
     * pending/executing calls); false is returned if the object has
     * pending/executing calls in which case it cannot be deactivated
     * @exception UnknownObjectException if object is not known (it may
     * already be inactive)
     * @exception ActivationException if group is not active
     * @exception RemoteException if call informing monitor fails
     * @since 1.2
     */
    public static boolean inactive(ActivationID id)
        throws UnknownObjectException, ActivationException, RemoteException
    {
        return ActivationGroup.currentGroup().inactiveObject(id);
    }

    /**
     * Revokes previous registration for the activation descriptor
     * associated with <code>id</code>. An object can no longer be
     * activated via that <code>id</code>.
     *
     * @param id the object's activation identifier
     * @exception UnknownObjectException if object (<code>id</code>) is unknown
     * @exception ActivationException if activation system is not running
     * @exception RemoteException if remote call to activation system fails
     * @since 1.2
     */
    public static void unregister(ActivationID id)
        throws UnknownObjectException, ActivationException, RemoteException
    {
        ActivationGroup.getSystem().unregisterObject(id);
    }

    /**
     * Registers an activation descriptor (with the specified location,
     * data, and restart mode) for the specified object, and exports that
     * object with the specified port.
     *
     * <p><strong>Note:</strong> Using this method (as well as the
     * <code>Activatable</code> constructors that both register and export
     * an activatable remote object) is strongly discouraged because the
     * actions of registering and exporting the remote object are
     * <i>not</i> guaranteed to be atomic.  Instead, an application should
     * register an activation descriptor and export a remote object
     * separately, so that exceptions can be handled properly.
     *
     * <p>This method invokes the {@link
     * #exportObject(Remote,String,MarshalledObject,boolean,int,RMIClientSocketFactory,RMIServerSocketFactory)
     * exportObject} method with the specified object, location, data,
     * restart mode, and port, and <code>null</code> for both client and
     * server socket factories, and then returns the resulting activation
     * identifier.
     *
     * @param obj the object being exported
     * @param location the object's code location
     * @param data the object's bootstrapping data
     * @param restart if true, the object is restarted (reactivated) when
     * either the activator is restarted or the object's activation group
     * is restarted after an unexpected crash; if false, the object is only
     * activated on demand.  Specifying <code>restart</code> to be
     * <code>true</code> does not force an initial immediate activation of
     * a newly registered object;  initial activation is lazy.
     * @param port the port on which the object is exported (an anonymous
     * port is used if port=0)
     * @return the activation identifier obtained from registering the
     * descriptor, <code>desc</code>, with the activation system
     * the wrong group
     * @exception ActivationException if activation group is not active
     * @exception RemoteException if object registration or export fails
     * @since 1.2
     **/
    public static ActivationID exportObject(Remote obj,
                                            String location,
                                            MarshalledObject<?> data,
                                            boolean restart,
                                            int port)
        throws ActivationException, RemoteException
    {
        return exportObject(obj, location, data, restart, port, null, null);
    }

    /**
     * Registers an activation descriptor (with the specified location,
     * data, and restart mode) for the specified object, and exports that
     * object with the specified port, and the specified client and server
     * socket factories.
     *
     * <p><strong>Note:</strong> Using this method (as well as the
     * <code>Activatable</code> constructors that both register and export
     * an activatable remote object) is strongly discouraged because the
     * actions of registering and exporting the remote object are
     * <i>not</i> guaranteed to be atomic.  Instead, an application should
     * register an activation descriptor and export a remote object
     * separately, so that exceptions can be handled properly.
     *
     * <p>This method first registers an activation descriptor for the
     * specified object as follows. It obtains the activation system by
     * invoking the method {@link ActivationGroup#getSystem
     * ActivationGroup.getSystem}.  This method then obtains an {@link
     * ActivationID} for the object by invoking the activation system's
     * {@link ActivationSystem#registerObject registerObject} method with
     * an {@link ActivationDesc} constructed with the specified object's
     * class name, and the specified location, data, and restart mode.  If
     * an exception occurs obtaining the activation system or registering
     * the activation descriptor, that exception is thrown to the caller.
     *
     * <p>Next, this method exports the object by invoking the {@link
     * #exportObject(Remote,ActivationID,int,RMIClientSocketFactory,RMIServerSocketFactory)
     * exportObject} method with the specified remote object, the
     * activation identifier obtained from registration, the specified
     * port, and the specified client and server socket factories.  If an
     * exception occurs exporting the object, this method attempts to
     * unregister the activation identifier (obtained from registration) by
     * invoking the activation system's {@link
     * ActivationSystem#unregisterObject unregisterObject} method with the
     * activation identifier.  If an exception occurs unregistering the
     * identifier, that exception is ignored, and the original exception
     * that occurred exporting the object is thrown to the caller.
     *
     * <p>Finally, this method invokes the {@link
     * ActivationGroup#activeObject activeObject} method on the activation
     * group in this VM with the activation identifier and the specified
     * remote object, and returns the activation identifier to the caller.
     *
     * @param obj the object being exported
     * @param location the object's code location
     * @param data the object's bootstrapping data
     * @param restart if true, the object is restarted (reactivated) when
     * either the activator is restarted or the object's activation group
     * is restarted after an unexpected crash; if false, the object is only
     * activated on demand.  Specifying <code>restart</code> to be
     * <code>true</code> does not force an initial immediate activation of
     * a newly registered object;  initial activation is lazy.
     * @param port the port on which the object is exported (an anonymous
     * port is used if port=0)
     * @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 the activation identifier obtained from registering the
     * descriptor with the activation system
     * @exception ActivationException if activation group is not active
     * @exception RemoteException if object registration or export fails
     * @since 1.2
     **/
    public static ActivationID exportObject(Remote obj,
                                            String location,
                                            MarshalledObject<?> data,
                                            boolean restart,
                                            int port,
                                            RMIClientSocketFactory csf,
                                            RMIServerSocketFactory ssf)
        throws ActivationException, RemoteException
    {
        ActivationDesc desc = new ActivationDesc(obj.getClass().getName(),
                                                 location, data, restart);
        /*
         * Register descriptor.
         */
        ActivationSystem system =  ActivationGroup.getSystem();
        ActivationID id = system.registerObject(desc);

        /*
         * Export object.
         */
        try {
            exportObject(obj, id, port, csf, ssf);
        } catch (RemoteException e) {
            /*
             * Attempt to unregister activation descriptor because export
             * failed and register/export should be atomic (see 4323621).
             */
            try {
                system.unregisterObject(id);
            } catch (Exception ex) {
            }
            /*
             * Report original exception.
             */
            throw e;
        }

        /*
         * This call can't fail (it is a local call, and the only possible
         * exception, thrown if the group is inactive, will not be thrown
         * because the group is not inactive).
         */
        ActivationGroup.currentGroup().activeObject(id, obj);

        return id;
    }

    /**
     * Export the activatable remote object to the RMI runtime to make
     * the object available to receive incoming calls. The object is
     * exported on an anonymous port, if <code>port</code> is zero. <p>
     *
     * During activation, this <code>exportObject</code> method should
     * be invoked explicitly by an "activatable" object, that does not
     * extend the <code>Activatable</code> class. There is no need for objects
     * that do extend the <code>Activatable</code> class to invoke this
     * method directly because the object is exported during construction.
     *
     * @return the stub for the activatable remote object
     * @param obj the remote object implementation
     * @param id the object's  activation identifier
     * @param port the port on which the object is exported (an anonymous
     * port is used if port=0)
     * @exception RemoteException if object export fails
     * @since 1.2
     */
    public static Remote exportObject(Remote obj,
                                      ActivationID id,
                                      int port)
        throws RemoteException
    {
        return exportObject(obj, new ActivatableServerRef(id, port));
    }

    /**
     * Export the activatable remote object to the RMI runtime to make
     * the object available to receive incoming calls. The object is
     * exported on an anonymous port, if <code>port</code> is zero. <p>
     *
     * During activation, this <code>exportObject</code> method should
     * be invoked explicitly by an "activatable" object, that does not
     * extend the <code>Activatable</code> class. There is no need for objects
     * that do extend the <code>Activatable</code> class to invoke this
     * method directly because the object is exported during construction.
     *
     * @return the stub for the activatable remote object
     * @param obj the remote object implementation
     * @param id the object's  activation identifier
     * @param port the port on which the object is exported (an anonymous
     * port is used if port=0)
     * @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
     * @exception RemoteException if object export fails
     * @since 1.2
     */
    public static Remote exportObject(Remote obj,
                                      ActivationID id,
                                      int port,
                                      RMIClientSocketFactory csf,
                                      RMIServerSocketFactory ssf)
        throws RemoteException
    {
        return exportObject(obj, new ActivatableServerRef(id, port, csf, ssf));
    }

    /**
     * Remove 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 NoSuchObjectException
    {
        return sun.rmi.transport.ObjectTable.unexportObject(obj, force);
    }

    /**
     * Exports the specified object using the specified server ref.
     */
    private static Remote exportObject(Remote obj, ActivatableServerRef sref)
        throws RemoteException
    {
        // if obj extends Activatable, set its ref.
        if (obj instanceof Activatable) {
            ((Activatable) obj).ref = sref;

        }
        return sref.exportObject(obj, null, false);
    }
}