Dépôt officiel du code source de l'ERP OpenConcerto

/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

 *

 * Copyright 2011 OpenConcerto, by ILM Informatique. All rights reserved.

 *

 * The contents of this file are subject to the terms of the GNU General Public License Version 3

 * only ("GPL"). You may not use this file except in compliance with the License. You can obtain a

 * copy of the License at http://www.gnu.org/licenses/gpl-3.0.html See the License for the specific

 * language governing permissions and limitations under the License.

 *

 * When distributing the software, include this License Header Notice in each file.

 */

 package org.openconcerto.utils.cache;

import org.openconcerto.utils.IScheduledFutureTask;

import java.util.Collections;

import java.util.HashMap;

import java.util.Iterator;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Set;

import java.util.concurrent.Callable;

import java.util.concurrent.RejectedExecutionException;

import java.util.concurrent.RunnableScheduledFuture;

import java.util.concurrent.ScheduledExecutorService;

import java.util.concurrent.ScheduledThreadPoolExecutor;

import java.util.concurrent.ThreadFactory;

import java.util.concurrent.TimeUnit;

import net.jcip.annotations.GuardedBy;

/**

 * Allow to pool the timer thread and the watchers for multiple {@link ICache}. Pooling the timer

 * saves resources, but pooling the watchers makes sure no events are lost when copying a value from

 * a cache to another. E.g. a watcher listens to a data, the data changes and copies its listeners

 * and begins to notify them. If one listener (before the watcher) hangs for a while, and then a new

 * watcher listens to the same data, it will never be notified of the previous event, no matter how

 * long ago it was generated. The only other option would be to also listen to the source cache item

 * but this is complicated and would need more memory allocation for each item.

 *

 * @author Sylvain

 *

 * @param <D> source data type, e.g. SQLTable.

 */

public final class ICacheSupport<D> {

    private final String name;

    private final ScheduledThreadPoolExecutor timer;

    @GuardedBy("this")

    private CacheWatcherFactory<? super D> watcherFactory;

    @GuardedBy("this")

    private final Map<D, CacheWatcher<? super D>> watchers;

    public ICacheSupport(final String name) {

        this(name, 2, TimeUnit.MINUTES);

    }

    public ICacheSupport(final String name, final long amout, final TimeUnit unit) {

        this.name = name;

        this.timer = new ScheduledThreadPoolExecutor(1, new ThreadFactory() {

            @Override

            public Thread newThread(Runnable r) {

                final Thread res = new Thread(r, "cache timeout thread for " + getName());

                res.setDaemon(true);

                res.setPriority(Thread.MIN_PRIORITY);

                return res;

            }

        }) {

            @Override

            protected <V> RunnableScheduledFuture<V> decorateTask(Runnable runnable, RunnableScheduledFuture<V> task) {

                return new IScheduledFutureTask<V>(task).setInnerRunnable(runnable);

            }

            @Override

            protected <V> RunnableScheduledFuture<V> decorateTask(Callable<V> callable, RunnableScheduledFuture<V> task) {

                return new IScheduledFutureTask<V>(task).setInnerCallable(callable);

            }

        };

        this.timer.scheduleWithFixedDelay(new Runnable() {

            @Override

            public void run() {

                purgeWatchers();

            }

        }, amout, amout, unit);

        this.watcherFactory = null;

        this.watchers = new HashMap<D, CacheWatcher<? super D>>();

    }

    public final String getName() {

        return this.name;

    }

    public boolean die() {

        final boolean didDie;

        final List<Runnable> runnables;

        synchronized (this) {

            didDie = !this.isDying();

            if (didDie) {

                runnables = this.getTimer().shutdownNow();

            } else {

                runnables = null;

            }

        }

        if (didDie) {

            // only CacheTimeOut are in our executor (plus the runnable for trimWatchers())

            // and all items in a cache (even the running ones) have a timeout (but they don't all

            // have a watcher : watcherFactory can be null and an item can have no data)

            for (final Runnable r : runnables) {

                final IScheduledFutureTask<?> sft = (IScheduledFutureTask<?>) r;

                if (sft.getInner() instanceof CacheTimeOut) {

                    sft.getInnerRunnable().run();

                }

            }

            synchronized (this) {

                purgeWatchers();

                assert this.watchers.isEmpty() : this.watchers.size() + " item(s) were not removed : " + this.watchers.values();

            }

        }

        return didDie;

    }

    public final boolean isDying() {

        return this.getTimer().isShutdown();

    }

    final ScheduledExecutorService getTimer() {

        return this.timer;

    }

    public final void purgeTimer() {

        this.timer.purge();

    }

    public synchronized void setWatcherFactory(CacheWatcherFactory<? super D> watcherFactory) {

        if (watcherFactory == null)

            throw new NullPointerException("Null factory");

        if (this.watcherFactory != null)

            throw new IllegalStateException("Already set to " + this.watcherFactory);

        this.watcherFactory = watcherFactory;

    }

    final synchronized CacheWatcher<? super D> watch(D data, final CacheItem<?, ?, D> item) {

        if (this.watcherFactory == null)

            return null;

        if (this.isDying())

            throw new RejectedExecutionException("Dead support");

        CacheWatcher<? super D> watcher = this.watchers.get(data);

        if (watcher == null) {

            try {

                watcher = this.watcherFactory.createWatcher(data);

            } catch (Exception e) {

                throw new IllegalStateException("Couldn't create watcher for " + data, e);

            }

            this.watchers.put(data, watcher);

        }

        watcher.add(item);

        return watcher;

    }

    final synchronized Map<D, CacheWatcher<? super D>> watch(Set<? extends D> data, final CacheItem<?, ?, D> item) {

        final Map<D, CacheWatcher<? super D>> res = new LinkedHashMap<D, CacheWatcher<? super D>>(data.size(), 1.0f);

        for (final D d : data) {

            final CacheWatcher<? super D> watcher = this.watch(d, item);

            if (watcher != null)

                res.put(d, watcher);

        }

        return Collections.unmodifiableMap(res);

    }

    public final synchronized int getWatchersCount() {

        return this.watchers.size();

    }

    public final synchronized int purgeWatchers() {

        final Iterator<Entry<D, CacheWatcher<? super D>>> iter = this.watchers.entrySet().iterator();

        while (iter.hasNext()) {

            final Entry<D, CacheWatcher<? super D>> e = iter.next();

            if (e.getValue().isEmpty())

                iter.remove();

        }

        return this.getWatchersCount();

    }

    final synchronized boolean dependsOn(D data) {

        return this.watchers.containsKey(data) && !this.watchers.get(data).isEmpty();

    }

}