abstractexecutorservice.java

来自「SRI international 发布的OAA框架软件」· Java 代码 · 共 232 行

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package edu.emory.mathcs.backport.java.util.concurrent;

import java.util.*;

import edu.emory.mathcs.backport.java.util.Assert;
import edu.emory.mathcs.backport.java.util.concurrent.helpers.*;

/**
 * Provides default implementation of {@link ExecutorService}
 * execution methods. This class implements the <tt>submit</tt>,
 * <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using the default
 * {@link FutureTask} class provided in this package.  For example,
 * the implementation of <tt>submit(Runnable)</tt> creates an
 * associated <tt>FutureTask</tt> that is executed and
 * returned. Subclasses overriding these methods to use different
 * {@link Future} implementations should do so consistently for each
 * of these methods.
 *
 * @since 1.5
 * @author Doug Lea
 */
public abstract class AbstractExecutorService implements ExecutorService {

    public Future submit(Runnable task) {
        if (task == null) throw new NullPointerException();
        FutureTask ftask = new FutureTask(task, null);
        execute(ftask);
        return ftask;
    }

    public Future submit(Runnable task, Object result) {
        if (task == null) throw new NullPointerException();
        FutureTask ftask = new FutureTask(task, result);
        execute(ftask);
        return ftask;
    }

    public Future submit(Callable task) {
        if (task == null) throw new NullPointerException();
        FutureTask ftask = new FutureTask(task);
        execute(ftask);
        return ftask;
    }

    /**
     * the main mechanics of invokeAny.
     */
    private Object doInvokeAny(Collection tasks,
                               boolean timed, long nanos)
        throws InterruptedException, ExecutionException, TimeoutException {
        if (tasks == null)
            throw new NullPointerException();
        int ntasks = tasks.size();
        if (ntasks == 0)
            throw new IllegalArgumentException();
        List futures= new ArrayList(ntasks);
        ExecutorCompletionService ecs =
            new ExecutorCompletionService(this);

        // For efficiency, especially in executors with limited
        // parallelism, check to see if previously submitted tasks are
        // done before submitting more of them. This interleaving
        // plus the exception mechanics account for messiness of main
        // loop.

        try {
            // Record exceptions so that if we fail to obtain any
            // result, we can throw the last exception we got.
            ExecutionException ee = null;
            long lastTime = (timed)? Utils.nanoTime() : 0;
            Iterator it = tasks.iterator();

            // Start one task for sure; the rest incrementally
            futures.add(ecs.submit((Callable)it.next()));
            --ntasks;
            int active = 1;

            for (;;) {
                Future f = ecs.poll();
                if (f == null) {
                    if (ntasks > 0) {
                        --ntasks;
                        futures.add(ecs.submit((Callable)it.next()));
                        ++active;
                    }
                    else if (active == 0)
                        break;
                    else if (timed) {
                        f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
                        if (f == null)
                            throw new TimeoutException();
                        long now = Utils.nanoTime();
                        nanos -= now - lastTime;
                        lastTime = now;
                    }
                    else
                        f = ecs.take();
                }
                if (f != null) {
                    --active;
                    try {
                        return f.get();
                    } catch(InterruptedException ie) {
                        throw ie;
                    } catch(ExecutionException eex) {
                        ee = eex;
                    } catch(RuntimeException rex) {
                        ee = new ExecutionException(rex);
                    }
                }
            }

            if (ee == null)
                ee = new ExecutionException();
            throw ee;

        } finally {
            for (Iterator f = futures.iterator(); f.hasNext();)
                ((Future)f.next()).cancel(true);
        }
    }

    public Object invokeAny(Collection tasks)
        throws InterruptedException, ExecutionException {
        try {
            return doInvokeAny(tasks, false, 0);
        } catch (TimeoutException cannotHappen) {
            Assert.assert_(false);
            return null;
        }
    }

    public Object invokeAny(Collection tasks,
                            long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException {
        return doInvokeAny(tasks, true, unit.toNanos(timeout));
    }

    public List invokeAll(Collection tasks) throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        List futures = new ArrayList(tasks.size());
        boolean done = false;
        try {
            for (Iterator t = tasks.iterator(); t.hasNext();) {
                FutureTask f = new FutureTask((Callable)t.next());
                futures.add(f);
                execute(f);
            }
            for (Iterator i = futures.iterator(); i.hasNext();) {
                Future f = (Future) i.next();
                if (!f.isDone()) {
                    try {
                        f.get();
                    } catch(CancellationException ignore) {
                    } catch(ExecutionException ignore) {
                    }
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (Iterator i = futures.iterator(); i.hasNext();) {
                    Future f = (Future) i.next();
                    f.cancel(true);
                }
        }
    }

    public List invokeAll(Collection tasks,
                          long timeout, TimeUnit unit)
        throws InterruptedException {
        if (tasks == null || unit == null)
            throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        List futures = new ArrayList(tasks.size());
        boolean done = false;
        try {
            for (Iterator t = tasks.iterator(); t.hasNext();)
                futures.add(new FutureTask((Callable)t.next()));

            long lastTime = Utils.nanoTime();

            // Interleave time checks and calls to execute in case
            // executor doesn't have any/much parallelism.
            Iterator it = futures.iterator();
            while (it.hasNext()) {
                execute((Runnable)(it.next()));
                long now = Utils.nanoTime();
                nanos -= (now - lastTime);
                lastTime = now;
                if (nanos <= 0)
                    return futures;
            }

            for (Iterator i = futures.iterator(); i.hasNext();) {
                Future f = (Future)i.next();
                if (!f.isDone()) {
                    if (nanos <= 0)
                        return futures;
                    try {
                        f.get(nanos, TimeUnit.NANOSECONDS);
                    } catch(CancellationException ignore) {
                    } catch(ExecutionException ignore) {
                    } catch(TimeoutException toe) {
                        return futures;
                    }
                    long now = Utils.nanoTime();
                    nanos -= now - lastTime;
                    lastTime = now;
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (Iterator i = futures.iterator(); i.hasNext();) {
                    Future f = (Future) i.next();
                    f.cancel(true);
                }
        }
    }

}