001/*
002 * Copyright (C) 2010 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkNotNull;
019import static java.util.Objects.requireNonNull;
020
021import com.google.common.annotations.GwtIncompatible;
022import com.google.errorprone.annotations.CanIgnoreReturnValue;
023import com.google.errorprone.annotations.CheckReturnValue;
024import java.lang.Thread.UncaughtExceptionHandler;
025import java.util.Locale;
026import java.util.concurrent.Executors;
027import java.util.concurrent.ThreadFactory;
028import java.util.concurrent.atomic.AtomicLong;
029import javax.annotation.CheckForNull;
030
031/**
032 * A ThreadFactory builder, providing any combination of these features:
033 *
034 * <ul>
035 *   <li>whether threads should be marked as {@linkplain Thread#setDaemon daemon} threads
036 *   <li>a {@linkplain ThreadFactoryBuilder#setNameFormat naming format}
037 *   <li>a {@linkplain Thread#setPriority thread priority}
038 *   <li>an {@linkplain Thread#setUncaughtExceptionHandler uncaught exception handler}
039 *   <li>a {@linkplain ThreadFactory#newThread backing thread factory}
040 * </ul>
041 *
042 * <p>If no backing thread factory is provided, a default backing thread factory is used as if by
043 * calling {@code setThreadFactory(}{@link Executors#defaultThreadFactory()}{@code )}.
044 *
045 * @author Kurt Alfred Kluever
046 * @since 4.0
047 */
048@CanIgnoreReturnValue
049@GwtIncompatible
050@ElementTypesAreNonnullByDefault
051public final class ThreadFactoryBuilder {
052  @CheckForNull private String nameFormat = null;
053  @CheckForNull private Boolean daemon = null;
054  @CheckForNull private Integer priority = null;
055  @CheckForNull private UncaughtExceptionHandler uncaughtExceptionHandler = null;
056  @CheckForNull private ThreadFactory backingThreadFactory = null;
057
058  /** Creates a new {@link ThreadFactory} builder. */
059  public ThreadFactoryBuilder() {}
060
061  /**
062   * Sets the naming format to use when naming threads ({@link Thread#setName}) which are created
063   * with this ThreadFactory.
064   *
065   * @param nameFormat a {@link String#format(String, Object...)}-compatible format String, to which
066   *     a unique integer (0, 1, etc.) will be supplied as the single parameter. This integer will
067   *     be unique to the built instance of the ThreadFactory and will be assigned sequentially. For
068   *     example, {@code "rpc-pool-%d"} will generate thread names like {@code "rpc-pool-0"}, {@code
069   *     "rpc-pool-1"}, {@code "rpc-pool-2"}, etc.
070   * @return this for the builder pattern
071   */
072  public ThreadFactoryBuilder setNameFormat(String nameFormat) {
073    String unused = format(nameFormat, 0); // fail fast if the format is bad or null
074    this.nameFormat = nameFormat;
075    return this;
076  }
077
078  /**
079   * Sets daemon or not for new threads created with this ThreadFactory.
080   *
081   * @param daemon whether or not new Threads created with this ThreadFactory will be daemon threads
082   * @return this for the builder pattern
083   */
084  public ThreadFactoryBuilder setDaemon(boolean daemon) {
085    this.daemon = daemon;
086    return this;
087  }
088
089  /**
090   * Sets the priority for new threads created with this ThreadFactory.
091   *
092   * @param priority the priority for new Threads created with this ThreadFactory
093   * @return this for the builder pattern
094   */
095  public ThreadFactoryBuilder setPriority(int priority) {
096    // Thread#setPriority() already checks for validity. These error messages
097    // are nicer though and will fail-fast.
098    checkArgument(
099        priority >= Thread.MIN_PRIORITY,
100        "Thread priority (%s) must be >= %s",
101        priority,
102        Thread.MIN_PRIORITY);
103    checkArgument(
104        priority <= Thread.MAX_PRIORITY,
105        "Thread priority (%s) must be <= %s",
106        priority,
107        Thread.MAX_PRIORITY);
108    this.priority = priority;
109    return this;
110  }
111
112  /**
113   * Sets the {@link UncaughtExceptionHandler} for new threads created with this ThreadFactory.
114   *
115   * @param uncaughtExceptionHandler the uncaught exception handler for new Threads created with
116   *     this ThreadFactory
117   * @return this for the builder pattern
118   */
119  public ThreadFactoryBuilder setUncaughtExceptionHandler(
120      UncaughtExceptionHandler uncaughtExceptionHandler) {
121    this.uncaughtExceptionHandler = checkNotNull(uncaughtExceptionHandler);
122    return this;
123  }
124
125  /**
126   * Sets the backing {@link ThreadFactory} for new threads created with this ThreadFactory. Threads
127   * will be created by invoking #newThread(Runnable) on this backing {@link ThreadFactory}.
128   *
129   * @param backingThreadFactory the backing {@link ThreadFactory} which will be delegated to during
130   *     thread creation.
131   * @return this for the builder pattern
132   * @see MoreExecutors
133   */
134  public ThreadFactoryBuilder setThreadFactory(ThreadFactory backingThreadFactory) {
135    this.backingThreadFactory = checkNotNull(backingThreadFactory);
136    return this;
137  }
138
139  /**
140   * Returns a new thread factory using the options supplied during the building process. After
141   * building, it is still possible to change the options used to build the ThreadFactory and/or
142   * build again. State is not shared amongst built instances.
143   *
144   * @return the fully constructed {@link ThreadFactory}
145   */
146  @CheckReturnValue
147  public ThreadFactory build() {
148    return doBuild(this);
149  }
150
151  // Split out so that the anonymous ThreadFactory can't contain a reference back to the builder.
152  // At least, I assume that's why. TODO(cpovirk): Check, and maybe add a test for this.
153  private static ThreadFactory doBuild(ThreadFactoryBuilder builder) {
154    String nameFormat = builder.nameFormat;
155    Boolean daemon = builder.daemon;
156    Integer priority = builder.priority;
157    UncaughtExceptionHandler uncaughtExceptionHandler = builder.uncaughtExceptionHandler;
158    ThreadFactory backingThreadFactory =
159        (builder.backingThreadFactory != null)
160            ? builder.backingThreadFactory
161            : Executors.defaultThreadFactory();
162    AtomicLong count = (nameFormat != null) ? new AtomicLong(0) : null;
163    return new ThreadFactory() {
164      @Override
165      public Thread newThread(Runnable runnable) {
166        Thread thread = backingThreadFactory.newThread(runnable);
167        if (nameFormat != null) {
168          // requireNonNull is safe because we create `count` if (and only if) we have a nameFormat.
169          thread.setName(format(nameFormat, requireNonNull(count).getAndIncrement()));
170        }
171        if (daemon != null) {
172          thread.setDaemon(daemon);
173        }
174        if (priority != null) {
175          thread.setPriority(priority);
176        }
177        if (uncaughtExceptionHandler != null) {
178          thread.setUncaughtExceptionHandler(uncaughtExceptionHandler);
179        }
180        return thread;
181      }
182    };
183  }
184
185  private static String format(String format, Object... args) {
186    return String.format(Locale.ROOT, format, args);
187  }
188}