001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.lang3.concurrent;
018    
019    import java.util.concurrent.Executors;
020    import java.util.concurrent.ThreadFactory;
021    import java.util.concurrent.atomic.AtomicLong;
022    
023    /**
024     * <p>
025     * An implementation of the {@code ThreadFactory} interface that provides some
026     * configuration options for the threads it creates.
027     * </p>
028     * <p>
029     * A {@code ThreadFactory} is used for instance by an {@code ExecutorService} to
030     * create the threads it uses for executing tasks. In many cases users do not
031     * have to care about a {@code ThreadFactory} because the default one used by an
032     * {@code ExecutorService} will do. However, if there are special requirements
033     * for the threads, a custom {@code ThreadFactory} has to be created.
034     * </p>
035     * <p>
036     * This class provides some frequently needed configuration options for the
037     * threads it creates. These are the following:
038     * <ul>
039     * <li>A name pattern for the threads created by this factory can be specified.
040     * This is often useful if an application uses multiple executor services for
041     * different purposes. If the names of the threads used by these services have
042     * meaningful names, log output or exception traces can be much easier to read.
043     * Naming patterns are <em>format strings</em> as used by the {@code
044     * String.format()} method. The string can contain the place holder {@code %d}
045     * which will be replaced by the number of the current thread ({@code
046     * ThreadFactoryImpl} keeps a counter of the threads it has already created).
047     * For instance, the naming pattern {@code "My %d. worker thread"} will result
048     * in thread names like {@code "My 1. worker thread"}, {@code
049     * "My 2. worker thread"} and so on.</li>
050     * <li>A flag whether the threads created by this factory should be daemon
051     * threads. This can impact the exit behavior of the current Java application
052     * because the JVM shuts down if there are only daemon threads running.</li>
053     * <li>The priority of the thread. Here an integer value can be provided. The
054     * {@code java.lang.Thread} class defines constants for valid ranges of priority
055     * values.</li>
056     * <li>The {@code UncaughtExceptionHandler} for the thread. This handler is
057     * called if an uncaught exception occurs within the thread.</li>
058     * </ul>
059     * </p>
060     * <p>
061     * {@code BasicThreadFactory} wraps another thread factory which actually
062     * creates new threads. The configuration options are set on the threads created
063     * by the wrapped thread factory. On construction time the factory to be wrapped
064     * can be specified. If none is provided, a default {@code ThreadFactory} is
065     * used.
066     * </p>
067     * <p>
068     * Instances of {@code BasicThreadFactory} are not created directly, but the
069     * nested {@code Builder} class is used for this purpose. Using the builder only
070     * the configuration options an application is interested in need to be set. The
071     * following example shows how a {@code BasicThreadFactory} is created and
072     * installed in an {@code ExecutorService}:
073     *
074     * <pre>
075     * // Create a factory that produces daemon threads with a naming pattern and
076     * // a priority
077     * BasicThreadFactory factory = new BasicThreadFactory.Builder()
078     *     .namingPattern(&quot;workerthread-%d&quot;)
079     *     .daemon(true)
080     *     .priority(Thread.MAX_PRIORITY)
081     *     .build();
082     * // Create an executor service for single-threaded execution
083     * ExecutorService exec = Executors.newSingleThreadExecutor(factory);
084     * </pre>
085     * </p>
086     *
087     * @since 3.0
088     * @version $Id: BasicThreadFactory.java 1079423 2011-03-08 16:38:09Z sebb $
089     */
090    public class BasicThreadFactory implements ThreadFactory {
091        /** A counter for the threads created by this factory. */
092        private final AtomicLong threadCounter;
093    
094        /** Stores the wrapped factory. */
095        private final ThreadFactory wrappedFactory;
096    
097        /** Stores the uncaught exception handler. */
098        private final Thread.UncaughtExceptionHandler uncaughtExceptionHandler;
099    
100        /** Stores the naming pattern for newly created threads. */
101        private final String namingPattern;
102    
103        /** Stores the priority. */
104        private final Integer priority;
105    
106        /** Stores the daemon status flag. */
107        private final Boolean daemonFlag;
108    
109        /**
110         * Creates a new instance of {@code ThreadFactoryImpl} and configures it
111         * from the specified {@code Builder} object.
112         *
113         * @param builder the {@code Builder} object
114         */
115        private BasicThreadFactory(Builder builder) {
116            if (builder.wrappedFactory == null) {
117                wrappedFactory = Executors.defaultThreadFactory();
118            } else {
119                wrappedFactory = builder.wrappedFactory;
120            }
121    
122            namingPattern = builder.namingPattern;
123            priority = builder.priority;
124            daemonFlag = builder.daemonFlag;
125            uncaughtExceptionHandler = builder.exceptionHandler;
126    
127            threadCounter = new AtomicLong();
128        }
129    
130        /**
131         * Returns the wrapped {@code ThreadFactory}. This factory is used for
132         * actually creating threads. This method never returns <b>null</b>. If no
133         * {@code ThreadFactory} was passed when this object was created, a default
134         * thread factory is returned.
135         *
136         * @return the wrapped {@code ThreadFactory}
137         */
138        public final ThreadFactory getWrappedFactory() {
139            return wrappedFactory;
140        }
141    
142        /**
143         * Returns the naming pattern for naming newly created threads. Result can
144         * be <b>null</b> if no naming pattern was provided.
145         *
146         * @return the naming pattern
147         */
148        public final String getNamingPattern() {
149            return namingPattern;
150        }
151    
152        /**
153         * Returns the daemon flag. This flag determines whether newly created
154         * threads should be daemon threads. If <b>true</b>, this factory object
155         * calls {@code setDaemon(true)} on the newly created threads. Result can be
156         * <b>null</b> if no daemon flag was provided at creation time.
157         *
158         * @return the daemon flag
159         */
160        public final Boolean getDaemonFlag() {
161            return daemonFlag;
162        }
163    
164        /**
165         * Returns the priority of the threads created by this factory. Result can
166         * be <b>null</b> if no priority was specified.
167         *
168         * @return the priority for newly created threads
169         */
170        public final Integer getPriority() {
171            return priority;
172        }
173    
174        /**
175         * Returns the {@code UncaughtExceptionHandler} for the threads created by
176         * this factory. Result can be <b>null</b> if no handler was provided.
177         *
178         * @return the {@code UncaughtExceptionHandler}
179         */
180        public final Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
181            return uncaughtExceptionHandler;
182        }
183    
184        /**
185         * Returns the number of threads this factory has already created. This
186         * class maintains an internal counter that is incremented each time the
187         * {@link #newThread(Runnable)} method is invoked.
188         *
189         * @return the number of threads created by this factory
190         */
191        public long getThreadCount() {
192            return threadCounter.get();
193        }
194    
195        /**
196         * Creates a new thread. This implementation delegates to the wrapped
197         * factory for creating the thread. Then, on the newly created thread the
198         * corresponding configuration options are set.
199         *
200         * @param r the {@code Runnable} to be executed by the new thread
201         * @return the newly created thread
202         */
203        public Thread newThread(Runnable r) {
204            Thread t = getWrappedFactory().newThread(r);
205            initializeThread(t);
206    
207            return t;
208        }
209    
210        /**
211         * Initializes the specified thread. This method is called by
212         * {@link #newThread(Runnable)} after a new thread has been obtained from
213         * the wrapped thread factory. It initializes the thread according to the
214         * options set for this factory.
215         *
216         * @param t the thread to be initialized
217         */
218        private void initializeThread(Thread t) {
219    
220            if (getNamingPattern() != null) {
221                Long count = Long.valueOf(threadCounter.incrementAndGet());
222                t.setName(String.format(getNamingPattern(), count));
223            }
224    
225            if (getUncaughtExceptionHandler() != null) {
226                t.setUncaughtExceptionHandler(getUncaughtExceptionHandler());
227            }
228    
229            if (getPriority() != null) {
230                t.setPriority(getPriority().intValue());
231            }
232    
233            if (getDaemonFlag() != null) {
234                t.setDaemon(getDaemonFlag().booleanValue());
235            }
236        }
237    
238        /**
239         * <p>
240         * A <em>builder</em> class for creating instances of {@code
241         * BasicThreadFactory}.
242         * </p>
243         * <p>
244         * Using this builder class instances of {@code BasicThreadFactory} can be
245         * created and initialized. The class provides methods that correspond to
246         * the configuration options supported by {@code BasicThreadFactory}. Method
247         * chaining is supported. Refer to the documentation of {@code
248         * BasicThreadFactory} for a usage example.
249         * </p>
250         *
251         * @version $Id: BasicThreadFactory.java 1079423 2011-03-08 16:38:09Z sebb $
252         */
253        public static class Builder 
254            implements org.apache.commons.lang3.builder.Builder<BasicThreadFactory> {
255            
256            /** The wrapped factory. */
257            private ThreadFactory wrappedFactory;
258    
259            /** The uncaught exception handler. */
260            private Thread.UncaughtExceptionHandler exceptionHandler;
261    
262            /** The naming pattern. */
263            private String namingPattern;
264    
265            /** The priority. */
266            private Integer priority;
267    
268            /** The daemon flag. */
269            private Boolean daemonFlag;
270    
271            /**
272             * Sets the {@code ThreadFactory} to be wrapped by the new {@code
273             * BasicThreadFactory}.
274             *
275             * @param factory the wrapped {@code ThreadFactory} (must not be
276             * <b>null</b>)
277             * @return a reference to this {@code Builder}
278             * @throws NullPointerException if the passed in {@code ThreadFactory}
279             * is <b>null</b>
280             */
281            public Builder wrappedFactory(ThreadFactory factory) {
282                if (factory == null) {
283                    throw new NullPointerException(
284                            "Wrapped ThreadFactory must not be null!");
285                }
286    
287                wrappedFactory = factory;
288                return this;
289            }
290    
291            /**
292             * Sets the naming pattern to be used by the new {@code
293             * BasicThreadFactory}.
294             *
295             * @param pattern the naming pattern (must not be <b>null</b>)
296             * @return a reference to this {@code Builder}
297             * @throws NullPointerException if the naming pattern is <b>null</b>
298             */
299            public Builder namingPattern(String pattern) {
300                if (pattern == null) {
301                    throw new NullPointerException(
302                            "Naming pattern must not be null!");
303                }
304    
305                namingPattern = pattern;
306                return this;
307            }
308    
309            /**
310             * Sets the daemon flag for the new {@code BasicThreadFactory}. If this
311             * flag is set to <b>true</b> the new thread factory will create daemon
312             * threads.
313             *
314             * @param f the value of the daemon flag
315             * @return a reference to this {@code Builder}
316             */
317            public Builder daemon(boolean f) {
318                daemonFlag = Boolean.valueOf(f);
319                return this;
320            }
321    
322            /**
323             * Sets the priority for the threads created by the new {@code
324             * BasicThreadFactory}.
325             *
326             * @param prio the priority
327             * @return a reference to this {@code Builder}
328             */
329            public Builder priority(int prio) {
330                priority = Integer.valueOf(prio);
331                return this;
332            }
333    
334            /**
335             * Sets the uncaught exception handler for the threads created by the
336             * new {@code BasicThreadFactory}.
337             *
338             * @param handler the {@code UncaughtExceptionHandler} (must not be
339             * <b>null</b>)
340             * @return a reference to this {@code Builder}
341             * @throws NullPointerException if the exception handler is <b>null</b>
342             */
343            public Builder uncaughtExceptionHandler(
344                    Thread.UncaughtExceptionHandler handler) {
345                if (handler == null) {
346                    throw new NullPointerException(
347                            "Uncaught exception handler must not be null!");
348                }
349    
350                exceptionHandler = handler;
351                return this;
352            }
353    
354            /**
355             * Resets this builder. All configuration options are set to default
356             * values. Note: If the {@link #build()} method was called, it is not
357             * necessary to call {@code reset()} explicitly because this is done
358             * automatically.
359             */
360            public void reset() {
361                wrappedFactory = null;
362                exceptionHandler = null;
363                namingPattern = null;
364                priority = null;
365                daemonFlag = null;
366            }
367    
368            /**
369             * Creates a new {@code BasicThreadFactory} with all configuration
370             * options that have been specified by calling methods on this builder.
371             * After creating the factory {@link #reset()} is called.
372             *
373             * @return the new {@code BasicThreadFactory}
374             */
375            public BasicThreadFactory build() {
376                BasicThreadFactory factory = new BasicThreadFactory(this);
377                reset();
378                return factory;
379            }
380        }
381    }