    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    }