Java example source code file (ActivationGroupImpl.java)

This example Java source code file (ActivationGroupImpl.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

activationexception, activationgroupimpl, activationid, activeentry, classloader, hashtable, illegalaccessexception, instantiationexception, invocationtargetexception, marshalledobject, net, network, nosuchmethodexception, reflection, remote, remoteexception, rmi, security, unknownobjectexception, util

The ActivationGroupImpl.java Java example source code

/*
 * Copyright (c) 1997, 2012, 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.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.net.ServerSocket;
import java.rmi.MarshalledObject;
import java.rmi.NoSuchObjectException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.activation.Activatable;
import java.rmi.activation.ActivationDesc;
import java.rmi.activation.ActivationException;
import java.rmi.activation.ActivationGroup;
import java.rmi.activation.ActivationGroupID;
import java.rmi.activation.ActivationID;
import java.rmi.activation.UnknownObjectException;
import java.rmi.server.RMIClassLoader;
import java.rmi.server.RMIServerSocketFactory;
import java.rmi.server.RMISocketFactory;
import java.rmi.server.UnicastRemoteObject;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import sun.rmi.registry.RegistryImpl;

/**
 * The default activation group implementation.
 *
 * @author      Ann Wollrath
 * @since       1.2
 * @see         java.rmi.activation.ActivationGroup
 */
public class ActivationGroupImpl extends ActivationGroup {

    // use serialVersionUID from JDK 1.2.2 for interoperability
    private static final long serialVersionUID = 5758693559430427303L;

    /** maps persistent IDs to activated remote objects */
    private final Hashtable<ActivationID,ActiveEntry> active =
        new Hashtable<>();
    private boolean groupInactive = false;
    private final ActivationGroupID groupID;
    private final List<ActivationID> lockedIDs = new ArrayList<>();

    /**
     * Creates a default activation group implementation.
     *
     * @param id the group's identifier
     * @param data ignored
     */
    public ActivationGroupImpl(ActivationGroupID id, MarshalledObject<?> data)
        throws RemoteException
    {
        super(id);
        groupID = id;

        /*
         * Unexport activation group impl and attempt to export it on
         * an unshared anonymous port.  See 4692286.
         */
        unexportObject(this, true);
        RMIServerSocketFactory ssf = new ServerSocketFactoryImpl();
        UnicastRemoteObject.exportObject(this, 0, null, ssf);

        if (System.getSecurityManager() == null) {
            try {
                // Provide a default security manager.
                System.setSecurityManager(new SecurityManager());

            } catch (Exception e) {
                throw new RemoteException("unable to set security manager", e);
            }
        }
    }

    /**
     * Trivial server socket factory used to export the activation group
     * impl on an unshared port.
     */
    private static class ServerSocketFactoryImpl
        implements RMIServerSocketFactory
    {
        public ServerSocket createServerSocket(int port) throws IOException
        {
            RMISocketFactory sf = RMISocketFactory.getSocketFactory();
            if (sf == null) {
                sf = RMISocketFactory.getDefaultSocketFactory();
            }
            return sf.createServerSocket(port);
        }
    }

    /*
     * Obtains a lock on the ActivationID id before returning. Allows only one
     * thread at a time to hold a lock on a particular id.  If the lock for id
     * is in use, all requests for an equivalent (in the Object.equals sense)
     * id will wait for the id to be notified and use the supplied id as the
     * next lock. The caller of "acquireLock" must execute the "releaseLock"
     * method" to release the lock and "notifyAll" waiters for the id lock
     * obtained from this method.  The typical usage pattern is as follows:
     *
     * try {
     *    acquireLock(id);
     *    // do stuff pertaining to id...
     * } finally {
     *    releaseLock(id);
     *    checkInactiveGroup();
     * }
     */
    private void acquireLock(ActivationID id) {

        ActivationID waitForID;

        for (;;) {

            synchronized (lockedIDs) {
                int index = lockedIDs.indexOf(id);
                if (index < 0) {
                    lockedIDs.add(id);
                    return;
                } else {
                    waitForID = lockedIDs.get(index);
                }
            }

            synchronized (waitForID) {
                synchronized (lockedIDs) {
                    int index = lockedIDs.indexOf(waitForID);
                    if (index < 0) continue;
                    ActivationID actualID = lockedIDs.get(index);
                    if (actualID != waitForID)
                        /*
                         * don't wait on an id that won't be notified.
                         */
                        continue;
                }

                try {
                    waitForID.wait();
                } catch (InterruptedException ignore) {
                }
            }
        }

    }

    /*
     * Releases the id lock obtained via the "acquireLock" method and then
     * notifies all threads waiting on the lock.
     */
    private void releaseLock(ActivationID id) {
        synchronized (lockedIDs) {
            id = lockedIDs.remove(lockedIDs.indexOf(id));
        }

        synchronized (id) {
            id.notifyAll();
        }
    }

    /**
     * Creates a new instance of an activatable remote object. The
     * <code>Activator calls this method to create an activatable
     * object in this group. This method should be idempotent; a call to
     * activate an already active object should return the previously
     * activated object.
     *
     * Note: this method assumes that the Activator will only invoke
     * newInstance for the same object in a serial fashion (i.e.,
     * the activator will not allow the group to see concurrent requests
     * to activate the same object.
     *
     * @param id the object's activation identifier
     * @param desc the object's activation descriptor
     * @return a marshalled object containing the activated object's stub
     */
    public MarshalledObject<? extends Remote>
                                      newInstance(final ActivationID id,
                                                  final ActivationDesc desc)
        throws ActivationException, RemoteException
    {
        RegistryImpl.checkAccess("ActivationInstantiator.newInstance");

        if (!groupID.equals(desc.getGroupID()))
            throw new ActivationException("newInstance in wrong group");

        try {
            acquireLock(id);
            synchronized (this) {
                if (groupInactive == true)
                    throw new InactiveGroupException("group is inactive");
            }

            ActiveEntry entry = active.get(id);
            if (entry != null)
                return entry.mobj;

            String className = desc.getClassName();

            final Class<? extends Remote> cl =
                RMIClassLoader.loadClass(desc.getLocation(), className)
                .asSubclass(Remote.class);
            Remote impl = null;

            final Thread t = Thread.currentThread();
            final ClassLoader savedCcl = t.getContextClassLoader();
            ClassLoader objcl = cl.getClassLoader();
            final ClassLoader ccl = covers(objcl, savedCcl) ? objcl : savedCcl;

            /*
             * Fix for 4164971: allow non-public activatable class
             * and/or constructor, create the activatable object in a
             * privileged block
             */
            try {
                /*
                 * The code below is in a doPrivileged block to
                 * protect against user code which code might have set
                 * a global socket factory (in which case application
                 * code would be on the stack).
                 */
                impl = AccessController.doPrivileged(
                      new PrivilegedExceptionAction<Remote>() {
                      public Remote run() throws InstantiationException,
                          NoSuchMethodException, IllegalAccessException,
                          InvocationTargetException
                      {
                          Constructor<? extends Remote> constructor =
                              cl.getDeclaredConstructor(
                                  ActivationID.class, MarshalledObject.class);
                          constructor.setAccessible(true);
                          try {
                              /*
                               * Fix for 4289544: make sure to set the
                               * context class loader to be the class
                               * loader of the impl class before
                               * constructing that class.
                               */
                              t.setContextClassLoader(ccl);
                              return constructor.newInstance(id,
                                                             desc.getData());
                          } finally {
                              t.setContextClassLoader(savedCcl);
                          }
                      }
                  });
            } catch (PrivilegedActionException pae) {
                Throwable e = pae.getException();

                // narrow the exception's type and rethrow it
                if (e instanceof InstantiationException) {
                    throw (InstantiationException) e;
                } else if (e instanceof NoSuchMethodException) {
                    throw (NoSuchMethodException) e;
                } else if (e instanceof IllegalAccessException) {
                    throw (IllegalAccessException) e;
                } else if (e instanceof InvocationTargetException) {
                    throw (InvocationTargetException) e;
                } else if (e instanceof RuntimeException) {
                    throw (RuntimeException) e;
                } else if (e instanceof Error) {
                    throw (Error) e;
                }
            }

            entry = new ActiveEntry(impl);
            active.put(id, entry);
            return entry.mobj;

        } catch (NoSuchMethodException | NoSuchMethodError e) {
            /* user forgot to provide activatable constructor?
             * or code recompiled and user forgot to provide
             *  activatable constructor?
             */
            throw new ActivationException
                ("Activatable object must provide an activation"+
                 " constructor", e );

        } catch (InvocationTargetException e) {
            throw new ActivationException("exception in object constructor",
                                          e.getTargetException());

        } catch (Exception e) {
            throw new ActivationException("unable to activate object", e);
        } finally {
            releaseLock(id);
            checkInactiveGroup();
        }
    }


   /**
    * The group's <code>inactiveObject method is called
    * indirectly via a call to the <code>Activatable.inactive
    * method. A remote object implementation must call
    * <code>Activatable's inactive method when
    * that object deactivates (the object deems that it is no longer
    * active). If the object does not call
    * <code>Activatable.inactive when it deactivates, the
    * object will never be garbage collected since the group keeps
    * strong references to the objects it creates. <p>
    *
    * The group's <code>inactiveObject method
    * unexports the remote object from the RMI runtime so that the
    * object can no longer receive incoming RMI calls. This call will
    * only succeed if the object has no pending/executing calls. If
    * the object does have pending/executing RMI calls, then false
    * will be returned.
    *
    * If the object has no pending/executing calls, the object is
    * removed from the RMI runtime and the group informs its
    * <code>ActivationMonitor (via the monitor's
    * <code>inactiveObject method) that the remote object is
    * not currently active so that the remote object will be
    * re-activated by the activator upon a subsequent activation
    * request.
    *
    * @param id the object's activation identifier
    * @returns 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 unknown (may already
    * be inactive)
    * @exception RemoteException if call informing monitor fails
    */
    public boolean inactiveObject(ActivationID id)
        throws ActivationException, UnknownObjectException, RemoteException
    {

        try {
            acquireLock(id);
            synchronized (this) {
                if (groupInactive == true)
                    throw new ActivationException("group is inactive");
            }

            ActiveEntry entry = active.get(id);
            if (entry == null) {
                // REMIND: should this be silent?
                throw new UnknownObjectException("object not active");
            }

            try {
                if (Activatable.unexportObject(entry.impl, false) == false)
                    return false;
            } catch (NoSuchObjectException allowUnexportedObjects) {
            }

            try {
                super.inactiveObject(id);
            } catch (UnknownObjectException allowUnregisteredObjects) {
            }

            active.remove(id);

        } finally {
            releaseLock(id);
            checkInactiveGroup();
        }

        return true;
    }

    /*
     * Determines if the group has become inactive and
     * marks it as such.
     */
    private void checkInactiveGroup() {
        boolean groupMarkedInactive = false;
        synchronized (this) {
            if (active.size() == 0 && lockedIDs.size() == 0 &&
                groupInactive == false)
            {
                groupInactive = true;
                groupMarkedInactive = true;
            }
        }

        if (groupMarkedInactive) {
            try {
                super.inactiveGroup();
            } catch (Exception ignoreDeactivateFailure) {
            }

            try {
                UnicastRemoteObject.unexportObject(this, true);
            } catch (NoSuchObjectException allowUnexportedGroup) {
            }
        }
    }

    /**
     * The group's <code>activeObject method is called when an
     * object is exported (either by <code>Activatable object
     * construction or an explicit call to
     * <code>Activatable.exportObject. The group must inform its
     * <code>ActivationMonitor that the object is active (via
     * the monitor's <code>activeObject method) if the group
     * hasn't already done so.
     *
     * @param id the object's identifier
     * @param obj the remote object implementation
     * @exception UnknownObjectException if object is not registered
     * @exception RemoteException if call informing monitor fails
     */
    public void activeObject(ActivationID id, Remote impl)
        throws ActivationException, UnknownObjectException, RemoteException
    {

        try {
            acquireLock(id);
            synchronized (this) {
                if (groupInactive == true)
                    throw new ActivationException("group is inactive");
            }
            if (!active.contains(id)) {
                ActiveEntry entry = new ActiveEntry(impl);
                active.put(id, entry);
                // created new entry, so inform monitor of active object
                try {
                    super.activeObject(id, entry.mobj);
                } catch (RemoteException e) {
                    // daemon can still find it by calling newInstance
                }
            }
        } finally {
            releaseLock(id);
            checkInactiveGroup();
        }
    }

    /**
     * Entry in table for active object.
     */
    private static class ActiveEntry {
        Remote impl;
        MarshalledObject<Remote> mobj;

        ActiveEntry(Remote impl) throws ActivationException {
            this.impl =  impl;
            try {
                this.mobj = new MarshalledObject<Remote>(impl);
            } catch (IOException e) {
                throw new
                    ActivationException("failed to marshal remote object", e);
            }
        }
    }

    /**
     * Returns true if the first argument is either equal to, or is a
     * descendant of, the second argument.  Null is treated as the root of
     * the tree.
     */
    private static boolean covers(ClassLoader sub, ClassLoader sup) {
        if (sup == null) {
            return true;
        } else if (sub == null) {
            return false;
        }
        do {
            if (sub == sup) {
                return true;
            }
            sub = sub.getParent();
        } while (sub != null);
        return false;
    }
}