001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
004//
005// http://www.apache.org/licenses/LICENSE-2.0
006//
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
012
013package org.apache.tapestry5.ioc.internal.services;
014
015import java.util.List;
016import java.util.Map;
017import java.util.concurrent.atomic.AtomicBoolean;
018import java.util.concurrent.atomic.AtomicInteger;
019
020import org.apache.tapestry5.ioc.Invokable;
021import org.apache.tapestry5.ioc.ObjectCreator;
022import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
023import org.apache.tapestry5.ioc.services.PerThreadValue;
024import org.apache.tapestry5.ioc.services.PerthreadManager;
025import org.apache.tapestry5.ioc.services.RegistryShutdownHub;
026import org.apache.tapestry5.ioc.services.ThreadCleanupListener;
027import org.slf4j.Logger;
028
029@SuppressWarnings("all")
030public class PerthreadManagerImpl implements PerthreadManager
031{
032    private final PerThreadValue<List<Runnable>> callbacksValue;
033
034    private static class MapHolder extends ThreadLocal<Map>
035    {
036        @Override
037        protected Map initialValue()
038        {
039            return CollectionFactory.newMap();
040        }
041    }
042
043    private final Logger logger;
044
045    private final MapHolder holder = new MapHolder();
046
047    private final AtomicInteger uuidGenerator = new AtomicInteger();
048
049    private final AtomicBoolean shutdown = new AtomicBoolean();
050
051    public PerthreadManagerImpl(Logger logger)
052    {
053        this.logger = logger;
054
055        callbacksValue = createValue();
056    }
057
058    public void registerForShutdown(RegistryShutdownHub hub)
059    {
060        hub.addRegistryShutdownListener(new Runnable()
061        {
062            @Override
063            public void run()
064            {
065                cleanup();
066                shutdown.set(true);
067            }
068        });
069    }
070
071    private Map getPerthreadMap()
072    {
073        // This is a degenerate case; it may not even exist; but if during registry shutdown somehow code executes
074        // that attempts to create new values or add new listeners, those go into a new map instance that is
075        // not referenced (and so immediately GCed).
076        if (shutdown.get())
077        {
078            return CollectionFactory.newMap();
079        }
080
081        return holder.get();
082    }
083
084    private List<Runnable> getCallbacks()
085    {
086        List<Runnable> result = callbacksValue.get();
087
088        if (result == null)
089        {
090            result = CollectionFactory.newList();
091            callbacksValue.set(result);
092        }
093
094        return result;
095    }
096
097    @Override
098    public void addThreadCleanupListener(final ThreadCleanupListener listener)
099    {
100        assert listener != null;
101
102        addThreadCleanupCallback(new Runnable()
103        {
104            @Override
105            public void run()
106            {
107                listener.threadDidCleanup();
108            }
109        });
110    }
111
112    @Override
113    public void addThreadCleanupCallback(Runnable callback)
114    {
115        assert callback != null;
116
117        getCallbacks().add(callback);
118    }
119
120    /**
121     * Instructs the hub to notify all its listeners (for the current thread).
122     * It also discards its list of listeners.
123     */
124    @Override
125    public void cleanup()
126    {
127        List<Runnable> callbacks = getCallbacks();
128
129        callbacksValue.set(null);
130
131        for (Runnable callback : callbacks)
132        {
133            try
134            {
135                callback.run();
136            } catch (Exception ex)
137            {
138                logger.warn(String.format("Error invoking callback %s: %s", callback, ex),
139                        ex);
140            }
141        }
142
143        // Listeners should not re-add themselves or store any per-thread state
144        // here, it will be lost.
145
146        // Discard the per-thread map of values, including the key that stores
147        // the listeners. This means that if a listener attempts to register
148        // new listeners, the new listeners will not be triggered and will be
149        // released to the GC.
150
151        holder.remove();
152    }
153
154    private static Object NULL_VALUE = new Object();
155
156    <T> ObjectCreator<T> createValue(final Object key, final ObjectCreator<T> delegate)
157    {
158        return new ObjectCreator<T>()
159        {
160            public T createObject()
161            {
162                Map map = getPerthreadMap();
163                T storedValue = (T) map.get(key);
164
165                if (storedValue != null)
166                {
167                    return (storedValue == NULL_VALUE) ? null : storedValue;
168                }
169
170                T newValue = delegate.createObject();
171
172                map.put(key, newValue == null ? NULL_VALUE : newValue);
173
174                return newValue;
175            }
176        };
177    }
178
179    public <T> ObjectCreator<T> createValue(ObjectCreator<T> delegate)
180    {
181        return createValue(uuidGenerator.getAndIncrement(), delegate);
182    }
183
184    <T> PerThreadValue<T> createValue(final Object key)
185    {
186        return new PerThreadValue<T>()
187        {
188            @Override
189            public T get()
190            {
191                return get(null);
192            }
193
194            @Override
195            public T get(T defaultValue)
196            {
197                Map map = getPerthreadMap();
198
199                Object storedValue = map.get(key);
200
201                if (storedValue == null)
202                {
203                    return defaultValue;
204                }
205
206                if (storedValue == NULL_VALUE)
207                {
208                    return null;
209                }
210
211                return (T) storedValue;
212            }
213
214            @Override
215            public T set(T newValue)
216            {
217                getPerthreadMap().put(key, newValue == null ? NULL_VALUE : newValue);
218
219                return newValue;
220            }
221
222            @Override
223            public boolean exists()
224            {
225                return getPerthreadMap().containsKey(key);
226            }
227        };
228    }
229
230    @Override
231    public <T> PerThreadValue<T> createValue()
232    {
233        return createValue(uuidGenerator.getAndIncrement());
234    }
235
236    @Override
237    public void run(Runnable runnable)
238    {
239        assert runnable != null;
240
241        try
242        {
243            runnable.run();
244        } finally
245        {
246            cleanup();
247        }
248    }
249
250    @Override
251    public <T> T invoke(Invokable<T> invokable)
252    {
253        try
254        {
255            return invokable.invoke();
256        } finally
257        {
258            cleanup();
259        }
260    }
261}