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