org.helios.apmrouter.catalog.api.impl.ThreadLocalizedMultiplexedInterceptor.java Source code

Introduction

Here is the source code for org.helios.apmrouter.catalog.api.impl.ThreadLocalizedMultiplexedInterceptor.java

Source

/**
 * Helios, OpenSource Monitoring
 * Brought to you by the Helios Development Group
 *
 * Copyright 2007, Helios Development Group and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 
 *
 */
package org.helios.apmrouter.catalog.api.impl;

import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.hibernate.EmptyInterceptor;
import org.hibernate.Interceptor;

/**
 * <p>Title: ThreadLocalizedMultiplexedInterceptor</p>
 * <p>Description: </p> 
 * <p>Company: Helios Development Group LLC</p>
 * @author Whitehead (nwhitehead AT heliosdev DOT org)
 * <p><code>org.helios.apmrouter.catalog.api.impl.ThreadLocalizedMultiplexedInterceptor</code></p>
 */

public class ThreadLocalizedMultiplexedInterceptor extends EmptyInterceptor {
    /**  */
    private static final long serialVersionUID = 978989473632853871L;
    /** A set of interceptors invoked for all calling threads */
    protected final Set<Interceptor> sharedInterceptors = Collections
            .synchronizedSet(new LinkedHashSet<Interceptor>());
    /** A set of interceptors registered by individual threads and scoped only to the registering thread */
    protected static final ThreadLocal<Set<Interceptor>> threadLocalInterceptors = new ThreadLocal<Set<Interceptor>>() {
        @Override
        protected Set<Interceptor> initialValue() {
            return new LinkedHashSet<Interceptor>(2);
        }
    };

    /** The singleton instance */
    private static volatile ThreadLocalizedMultiplexedInterceptor instance = null;
    /** The singleton instance ctor lock */
    private static final Object lock = new Object();

    /**
     * Acquires a ThreadLocalizedMultiplexedInterceptor instance.
     * If the shared version has been created, that will be returned.
     * Otherwise, a new instance is created for each call to this method.
     * @return a ThreadLocalizedMultiplexedInterceptor
     */
    public static ThreadLocalizedMultiplexedInterceptor getInstance() {
        if (instance == null) {
            synchronized (lock) {
                if (instance == null) {
                    return new ThreadLocalizedMultiplexedInterceptor();
                }
            }
        }
        return instance;
    }

    /**
     * Acquires the shared ThreadLocalizedMultiplexedInterceptor and initializes it if it has not been initialized already.
     * @param interceptors A map of interceptors keyed by an integer representing the order of execution
     * @return the shared ThreadLocalizedMultiplexedInterceptor
     */
    public static ThreadLocalizedMultiplexedInterceptor getInstance(Map<Integer, Interceptor> interceptors) {
        if (instance == null) {
            synchronized (lock) {
                if (instance == null) {
                    instance = new ThreadLocalizedMultiplexedInterceptor(interceptors);
                }
            }
        }
        return instance;
    }

    /**
     * Creates a new ThreadLocalizedMultiplexedInterceptor
     */
    private ThreadLocalizedMultiplexedInterceptor() {

    }

    /**
     * Creates a new ThreadLocalizedMultiplexedInterceptor
     * @param interceptors The shared interceptor stack
     */
    private ThreadLocalizedMultiplexedInterceptor(Map<Integer, Interceptor> interceptors) {
        if (interceptors != null) {
            TreeMap<Integer, Interceptor> sortedMap = new TreeMap<Integer, Interceptor>(interceptors);
            for (Interceptor interceptor : sortedMap.values()) {
                if (interceptor == null)
                    continue;
                sharedInterceptors.add(interceptor);
            }
        }
    }

    /**
     * Registers the passed interceptor for execution scoped to the calling thread
     * @param interceptor the interceptor to register
     */
    public void registerThreadLocalInterceptor(Interceptor interceptor) {
        if (interceptor != null) {
            threadLocalInterceptors.get().add(interceptor);
        }
    }

    /**
     * Unregisters the passed interceptor from the calling thread's scoped interceptor stack.
     * @param interceptor the interceptor to remove.
     */
    public void unregisterThreadLocalInterceptor(Interceptor interceptor) {
        if (interceptor != null) {
            threadLocalInterceptors.get().remove(interceptor);
            if (threadLocalInterceptors.get().isEmpty()) {
                threadLocalInterceptors.remove();
            }
        }
    }

}