Tomcat example source code file (StandardThreadExecutor.java)

This example Tomcat source code file (StandardThreadExecutor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

atomicinteger, executor, lifecyclesupport, rejectedexecutionexception, standardthreadexecutor, string, string, taskqueue, taskqueue, taskthreadfactory, taskthreadfactory, thread, threading, threadpoolexecutor, threadpoolexecutor, threads, util

The Tomcat StandardThreadExecutor.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.catalina.core;

import java.util.Collection;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.catalina.Executor;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleListener;
import org.apache.catalina.util.LifecycleSupport;
import java.util.concurrent.RejectedExecutionException;

public class StandardThreadExecutor implements Executor {
    
    // ---------------------------------------------- Properties
    protected int threadPriority = Thread.NORM_PRIORITY;

    protected boolean daemon = true;
    
    protected String namePrefix = "tomcat-exec-";
    
    protected int maxThreads = 200;
    
    protected int minSpareThreads = 25;
    
    protected int maxIdleTime = 60000;
    
    protected ThreadPoolExecutor executor = null;
    
    protected String name;
    
    private LifecycleSupport lifecycle = new LifecycleSupport(this);
    // ---------------------------------------------- Constructors
    public StandardThreadExecutor() {
        //empty constructor for the digester
    }
    

    
    // ---------------------------------------------- Public Methods
    public void start() throws LifecycleException {
        lifecycle.fireLifecycleEvent(BEFORE_START_EVENT, null);
        TaskQueue taskqueue = new TaskQueue();
        TaskThreadFactory tf = new TaskThreadFactory(namePrefix);
        lifecycle.fireLifecycleEvent(START_EVENT, null);
        executor = new ThreadPoolExecutor(getMinSpareThreads(), getMaxThreads(), maxIdleTime, TimeUnit.MILLISECONDS,taskqueue, tf);
        taskqueue.setParent( (ThreadPoolExecutor) executor);
        lifecycle.fireLifecycleEvent(AFTER_START_EVENT, null);
    }
    
    public void stop() throws LifecycleException{
        lifecycle.fireLifecycleEvent(BEFORE_STOP_EVENT, null);
        lifecycle.fireLifecycleEvent(STOP_EVENT, null);
        if ( executor != null ) executor.shutdown();
        executor = null;
        lifecycle.fireLifecycleEvent(AFTER_STOP_EVENT, null);
    }
    
    public void execute(Runnable command) {
        if ( executor != null ) {
            try {
                executor.execute(command);
            } catch (RejectedExecutionException rx) {
                //there could have been contention around the queue
                if ( !( (TaskQueue) executor.getQueue()).force(command) ) throw new RejectedExecutionException();
            }
        } else throw new IllegalStateException("StandardThreadPool not started.");
    }

    public int getThreadPriority() {
        return threadPriority;
    }

    public boolean isDaemon() {

        return daemon;
    }

    public String getNamePrefix() {
        return namePrefix;
    }

    public int getMaxIdleTime() {
        return maxIdleTime;
    }

    public int getMaxThreads() {
        return maxThreads;
    }

    public int getMinSpareThreads() {
        return minSpareThreads;
    }

    public String getName() {
        return name;
    }

    public void setThreadPriority(int threadPriority) {
        this.threadPriority = threadPriority;
    }

    public void setDaemon(boolean daemon) {
        this.daemon = daemon;
    }

    public void setNamePrefix(String namePrefix) {
        this.namePrefix = namePrefix;
    }

    public void setMaxIdleTime(int maxIdleTime) {
        this.maxIdleTime = maxIdleTime;
    }

    public void setMaxThreads(int maxThreads) {
        this.maxThreads = maxThreads;
    }

    public void setMinSpareThreads(int minSpareThreads) {
        this.minSpareThreads = minSpareThreads;
    }

    public void setName(String name) {
        this.name = name;
    }
    
    /**
     * Add a LifecycleEvent listener to this component.
     *
     * @param listener The listener to add
     */
    public void addLifecycleListener(LifecycleListener listener) {
        lifecycle.addLifecycleListener(listener);
    }


    /**
     * Get the lifecycle listeners associated with this lifecycle. If this 
     * Lifecycle has no listeners registered, a zero-length array is returned.
     */
    public LifecycleListener[] findLifecycleListeners() {
        return lifecycle.findLifecycleListeners();
    }


    /**
     * Remove a LifecycleEvent listener from this component.
     *
     * @param listener The listener to remove
     */
    public void removeLifecycleListener(LifecycleListener listener) {
        lifecycle.removeLifecycleListener(listener);
    }

    // Statistics from the thread pool
    public int getActiveCount() {
        return (executor != null) ? executor.getActiveCount() : 0;
    }

    public long getCompletedTaskCount() {
        return (executor != null) ? executor.getCompletedTaskCount() : 0;
    }

    public int getCorePoolSize() {
        return (executor != null) ? executor.getCorePoolSize() : 0;
    }

    public int getLargestPoolSize() {
        return (executor != null) ? executor.getLargestPoolSize() : 0;
    }

    public int getPoolSize() {
        return (executor != null) ? executor.getPoolSize() : 0;
    }

    // ---------------------------------------------- TaskQueue Inner Class
    class TaskQueue extends LinkedBlockingQueue<Runnable> {
        ThreadPoolExecutor parent = null;

        public TaskQueue() {
            super();
        }

        public TaskQueue(int initialCapacity) {
            super(initialCapacity);
        }

        public TaskQueue(Collection<? extends Runnable> c) {
            super(c);
        }

        public void setParent(ThreadPoolExecutor tp) {
            parent = tp;
        }
        
        public boolean force(Runnable o) {
            if ( parent.isShutdown() ) throw new RejectedExecutionException("Executor not running, can't force a command into the queue");
            return super.offer(o); //forces the item onto the queue, to be used if the task is rejected
        }

        public boolean offer(Runnable o) {
            //we can't do any checks
            if (parent==null) return super.offer(o);
            //we are maxed out on threads, simply queue the object
            if (parent.getPoolSize() == parent.getMaximumPoolSize()) return super.offer(o);
            //we have idle threads, just add it to the queue
            //this is an approximation, so it could use some tuning
            if (parent.getActiveCount()<(parent.getPoolSize())) return super.offer(o);
            //if we have less threads than maximum force creation of a new thread
            if (parent.getPoolSize()<parent.getMaximumPoolSize()) return false;
            //if we reached here, we need to add it to the queue
            return super.offer(o);
        }
    }

    // ---------------------------------------------- ThreadFactory Inner Class
    class TaskThreadFactory implements ThreadFactory {
        final ThreadGroup group;
        final AtomicInteger threadNumber = new AtomicInteger(1);
        final String namePrefix;

        TaskThreadFactory(String namePrefix) {
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
            this.namePrefix = namePrefix;
        }

        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement());
            t.setDaemon(daemon);
            t.setPriority(getThreadPriority());
            return t;
        }
    }


}