Java example source code file (Session.java)

This example Java source code file (Session.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

atomicinteger, comparable, internal, max_idle_time, phantomreference, pkcs11exception, providerexception, referencequeue, security, sessionref, token, treeset, util

The Session.java Java example source code

/*
 * Copyright (c) 2003, 2011, 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.security.pkcs11;

import java.lang.ref.*;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;

import java.security.*;

import sun.security.pkcs11.wrapper.*;

/**
 * A session object. Sessions are obtained via the SessionManager,
 * see there for details. Most code will only ever need one method in
 * this class, the id() method to obtain the session id.
 *
 * @author  Andreas Sterbenz
 * @since   1.5
 */
final class Session implements Comparable<Session> {

    // time after which to close idle sessions, in milliseconds (3 minutes)
    private final static long MAX_IDLE_TIME = 3 * 60 * 1000;

    // token instance
    final Token token;

    // session id
    private final long id;

    // number of objects created within this session
    private final AtomicInteger createdObjects;

    // time this session was last used
    // not synchronized/volatile for performance, so may be unreliable
    // this could lead to idle sessions being closed early, but that is harmless
    private long lastAccess;

    private final SessionRef sessionRef;

    Session(Token token, long id) {
        this.token = token;
        this.id = id;
        createdObjects = new AtomicInteger();
        id();
        sessionRef = new SessionRef(this, id, token);
    }

    public int compareTo(Session other) {
        if (this.lastAccess == other.lastAccess) {
            return 0;
        } else {
            return (this.lastAccess < other.lastAccess) ? -1 : 1;
        }
    }

    boolean isLive(long currentTime) {
        return currentTime - lastAccess < MAX_IDLE_TIME;
    }

    long idInternal() {
        return id;
    }

    long id() {
        if (token.isPresent(this.id) == false) {
            throw new ProviderException("Token has been removed");
        }
        lastAccess = System.currentTimeMillis();
        return id;
    }

    void addObject() {
        int n = createdObjects.incrementAndGet();
        // XXX update statistics in session manager if n == 1
    }

    void removeObject() {
        int n = createdObjects.decrementAndGet();
        if (n == 0) {
            token.sessionManager.demoteObjSession(this);
        } else if (n < 0) {
            throw new ProviderException("Internal error: objects created " + n);
        }
    }

    boolean hasObjects() {
        return createdObjects.get() != 0;
    }

    void close() {
        if (hasObjects()) {
            throw new ProviderException(
                "Internal error: close session with active objects");
        }
        sessionRef.dispose();
    }
}

/*
 * NOTE: Use PhantomReference here and not WeakReference
 * otherwise the sessions maybe closed before other objects
 * which are still being finalized.
 */
final class SessionRef extends PhantomReference<Session>
        implements Comparable<SessionRef> {

    private static ReferenceQueue<Session> refQueue =
        new ReferenceQueue<Session>();

    private static Set<SessionRef> refList =
        Collections.synchronizedSortedSet(new TreeSet<SessionRef>());

    static ReferenceQueue<Session> referenceQueue() {
        return refQueue;
    }

    static int totalCount() {
        return refList.size();
    }

    private static void drainRefQueueBounded() {
        while (true) {
            SessionRef next = (SessionRef) refQueue.poll();
            if (next == null) break;
            next.dispose();
        }
    }

    // handle to the native session
    private long id;
    private Token token;

    SessionRef(Session session, long id, Token token) {
        super(session, refQueue);
        this.id = id;
        this.token = token;
        refList.add(this);
        // TBD: run at some interval and not every time?
        drainRefQueueBounded();
    }

    void dispose() {
        refList.remove(this);
        try {
            if (token.isPresent(id)) {
                token.p11.C_CloseSession(id);
            }
        } catch (PKCS11Exception e1) {
            // ignore
        } catch (ProviderException e2) {
            // ignore
        } finally {
            this.clear();
        }
    }

    public int compareTo(SessionRef other) {
        if (this.id == other.id) {
            return 0;
        } else {
            return (this.id < other.id) ? -1 : 1;
        }
    }
}