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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.jboss.netty.util;

import org.jboss.netty.logging.InternalLogger;
import org.jboss.netty.logging.InternalLoggerFactory;


/**
 * A {@link Runnable} that changes the current thread name and reverts it back
 * when its execution ends.  To change the default thread names set by Netty,
 * use {@link #setThreadNameDeterminer(ThreadNameDeterminer)}.
 *
 * @apiviz.landmark
 * @apiviz.has org.jboss.netty.util.ThreadNameDeterminer oneway - -
 */
public class ThreadRenamingRunnable implements Runnable {

    private static final InternalLogger logger =
        InternalLoggerFactory.getInstance(ThreadRenamingRunnable.class);

    private static volatile ThreadNameDeterminer threadNameDeterminer =
        ThreadNameDeterminer.PROPOSED;
    private final ThreadNameDeterminer determiner;

    /**
     * Returns the {@link ThreadNameDeterminer} which overrides the proposed
     * new thread name.
     */
    public static ThreadNameDeterminer getThreadNameDeterminer() {
        return threadNameDeterminer;
    }

    /**
     * Sets the {@link ThreadNameDeterminer} which overrides the proposed new
     * thread name.  Please note that the specified {@link ThreadNameDeterminer}
     * affects only new {@link ThreadRenamingRunnable}s; the existing instances
     * are not affected at all.  Therefore, you should make sure to call this
     * method at the earliest possible point (i.e. before any Netty worker
     * thread starts) for consistent thread naming.  Otherwise, you might see
     * the default thread names and the new names appear at the same time in
     * the full thread dump.
     */
    public static void setThreadNameDeterminer(ThreadNameDeterminer threadNameDeterminer) {
        if (threadNameDeterminer == null) {
            throw new NullPointerException("threadNameDeterminer");
        }
        ThreadRenamingRunnable.threadNameDeterminer = threadNameDeterminer;
    }

    private final Runnable runnable;
    private final String proposedThreadName;

    /**
     * Creates a new instance which wraps the specified {@code runnable}
     * and changes the thread name to the specified thread name when the
     * specified {@code runnable} is running.
     */
    public ThreadRenamingRunnable(Runnable runnable, String proposedThreadName, ThreadNameDeterminer determiner) {
        if (runnable == null) {
            throw new NullPointerException("runnable");
        }
        if (proposedThreadName == null) {
            throw new NullPointerException("proposedThreadName");
        }
        this.runnable = runnable;
        this.determiner = determiner;
        this.proposedThreadName = proposedThreadName;
    }

    public ThreadRenamingRunnable(Runnable runnable, String proposedThreadName) {
        this(runnable, proposedThreadName, null);
    }

    public void run() {
        final Thread currentThread = Thread.currentThread();
        final String oldThreadName = currentThread.getName();
        final String newThreadName = getNewThreadName(oldThreadName);

        // Change the thread name before starting the actual runnable.
        boolean renamed = false;
        if (!oldThreadName.equals(newThreadName)) {
            try {
                currentThread.setName(newThreadName);
                renamed = true;
            } catch (SecurityException e) {
                logger.debug(
                        "Failed to rename a thread " +
                        "due to security restriction.", e);
            }
        }

        // Run the actual runnable and revert the name back when it ends.
        try {
            runnable.run();
        } finally {
            if (renamed) {
                // Revert the name back if the current thread was renamed.
                // We do not check the exception here because we know it works.
                currentThread.setName(oldThreadName);
            }
        }
    }

    private String getNewThreadName(String currentThreadName) {
        String newThreadName = null;

        try {
            ThreadNameDeterminer nameDeterminer = determiner;
            if (nameDeterminer == null) {
                nameDeterminer = getThreadNameDeterminer();
            }
            newThreadName =
                nameDeterminer.determineThreadName(
                        currentThreadName, proposedThreadName);
        } catch (Throwable t) {
            logger.warn("Failed to determine the thread name", t);
        }

        return newThreadName == null? currentThreadName : newThreadName;
    }
}