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Apache Commons Lang, a package of Java utility classes for the
classes that are in java.lang's hierarchy, or are considered to be so
standard as to justify existence in java.lang.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.lang3.concurrent;
import java.lang.Thread.UncaughtExceptionHandler;
import java.util.Objects;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicLong;
/**
* An implementation of the {@link ThreadFactory} interface that provides some
* configuration options for the threads it creates.
*
*
* A {@link ThreadFactory} is used for instance by an {@link ExecutorService} to
* create the threads it uses for executing tasks. In many cases users do not
* have to care about a {@link ThreadFactory} because the default one used by an
* {@link ExecutorService} will do. However, if there are special requirements
* for the threads, a custom {@link ThreadFactory} has to be created.
*
*
* This class provides some frequently needed configuration options for the
* threads it creates. These are the following:
*
*
* - A name pattern for the threads created by this factory can be specified.
* This is often useful if an application uses multiple executor services for
* different purposes. If the names of the threads used by these services have
* meaningful names, log output or exception traces can be much easier to read.
* Naming patterns are format strings as used by the {@code
* String.format()} method. The string can contain the place holder {@code %d}
* which will be replaced by the number of the current thread ({@code
* ThreadFactoryImpl} keeps a counter of the threads it has already created).
* For instance, the naming pattern {@code "My %d. worker thread"} will result
* in thread names like {@code "My 1. worker thread"}, {@code
* "My 2. worker thread"} and so on.
* - A flag whether the threads created by this factory should be daemon
* threads. This can impact the exit behavior of the current Java application
* because the JVM shuts down if there are only daemon threads running.
* - The priority of the thread. Here an integer value can be provided. The
* {@code java.lang.Thread} class defines constants for valid ranges of priority
* values.
* - The {@link UncaughtExceptionHandler} for the thread. This handler is
* called if an uncaught exception occurs within the thread.
*
*
* {@link BasicThreadFactory} wraps another thread factory which actually
* creates new threads. The configuration options are set on the threads created
* by the wrapped thread factory. On construction time the factory to be wrapped
* can be specified. If none is provided, a default {@link ThreadFactory} is
* used.
*
*
* Instances of {@link BasicThreadFactory} are not created directly, but the
* nested {@link Builder} class is used for this purpose. Using the builder only
* the configuration options an application is interested in need to be set. The
* following example shows how a {@link BasicThreadFactory} is created and
* installed in an {@link ExecutorService}:
*
*
*
* // Create a factory that produces daemon threads with a naming pattern and
* // a priority
* BasicThreadFactory factory = new BasicThreadFactory.Builder()
* .namingPattern("workerthread-%d")
* .daemon(true)
* .priority(Thread.MAX_PRIORITY)
* .build();
* // Create an executor service for single-threaded execution
* ExecutorService exec = Executors.newSingleThreadExecutor(factory);
*
*
* @since 3.0
*/
public class BasicThreadFactory implements ThreadFactory {
/** A counter for the threads created by this factory. */
private final AtomicLong threadCounter;
/** Stores the wrapped factory. */
private final ThreadFactory wrappedFactory;
/** Stores the uncaught exception handler. */
private final Thread.UncaughtExceptionHandler uncaughtExceptionHandler;
/** Stores the naming pattern for newly created threads. */
private final String namingPattern;
/** Stores the priority. */
private final Integer priority;
/** Stores the daemon status flag. */
private final Boolean daemon;
/**
* Creates a new instance of {@link ThreadFactory} and configures it
* from the specified {@link Builder} object.
*
* @param builder the {@link Builder} object
*/
private BasicThreadFactory(final Builder builder) {
if (builder.wrappedFactory == null) {
wrappedFactory = Executors.defaultThreadFactory();
} else {
wrappedFactory = builder.wrappedFactory;
}
namingPattern = builder.namingPattern;
priority = builder.priority;
daemon = builder.daemon;
uncaughtExceptionHandler = builder.exceptionHandler;
threadCounter = new AtomicLong();
}
/**
* Returns the wrapped {@link ThreadFactory}. This factory is used for
* actually creating threads. This method never returns null. If no
* {@link ThreadFactory} was passed when this object was created, a default
* thread factory is returned.
*
* @return the wrapped {@link ThreadFactory}
*/
public final ThreadFactory getWrappedFactory() {
return wrappedFactory;
}
/**
* Returns the naming pattern for naming newly created threads. Result can
* be null if no naming pattern was provided.
*
* @return the naming pattern
*/
public final String getNamingPattern() {
return namingPattern;
}
/**
* Returns the daemon flag. This flag determines whether newly created
* threads should be daemon threads. If true, this factory object
* calls {@code setDaemon(true)} on the newly created threads. Result can be
* null if no daemon flag was provided at creation time.
*
* @return the daemon flag
*/
public final Boolean getDaemonFlag() {
return daemon;
}
/**
* Returns the priority of the threads created by this factory. Result can
* be null if no priority was specified.
*
* @return the priority for newly created threads
*/
public final Integer getPriority() {
return priority;
}
/**
* Returns the {@link UncaughtExceptionHandler} for the threads created by
* this factory. Result can be null if no handler was provided.
*
* @return the {@link UncaughtExceptionHandler}
*/
public final Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
return uncaughtExceptionHandler;
}
/**
* Returns the number of threads this factory has already created. This
* class maintains an internal counter that is incremented each time the
* {@link #newThread(Runnable)} method is invoked.
*
* @return the number of threads created by this factory
*/
public long getThreadCount() {
return threadCounter.get();
}
/**
* Creates a new thread. This implementation delegates to the wrapped
* factory for creating the thread. Then, on the newly created thread the
* corresponding configuration options are set.
*
* @param runnable the {@link Runnable} to be executed by the new thread
* @return the newly created thread
*/
@Override
public Thread newThread(final Runnable runnable) {
final Thread thread = getWrappedFactory().newThread(runnable);
initializeThread(thread);
return thread;
}
/**
* Initializes the specified thread. This method is called by
* {@link #newThread(Runnable)} after a new thread has been obtained from
* the wrapped thread factory. It initializes the thread according to the
* options set for this factory.
*
* @param thread the thread to be initialized
*/
private void initializeThread(final Thread thread) {
if (getNamingPattern() != null) {
final Long count = Long.valueOf(threadCounter.incrementAndGet());
thread.setName(String.format(getNamingPattern(), count));
}
if (getUncaughtExceptionHandler() != null) {
thread.setUncaughtExceptionHandler(getUncaughtExceptionHandler());
}
if (getPriority() != null) {
thread.setPriority(getPriority().intValue());
}
if (getDaemonFlag() != null) {
thread.setDaemon(getDaemonFlag().booleanValue());
}
}
/**
* A builder class for creating instances of {@code
* BasicThreadFactory}.
*
*
* Using this builder class instances of {@link BasicThreadFactory} can be
* created and initialized. The class provides methods that correspond to
* the configuration options supported by {@link BasicThreadFactory}. Method
* chaining is supported. Refer to the documentation of {@code
* BasicThreadFactory} for a usage example.
*
*
*/
public static class Builder
implements org.apache.commons.lang3.builder.Builder {
/** The wrapped factory. */
private ThreadFactory wrappedFactory;
/** The uncaught exception handler. */
private Thread.UncaughtExceptionHandler exceptionHandler;
/** The naming pattern. */
private String namingPattern;
/** The priority. */
private Integer priority;
/** The daemon flag. */
private Boolean daemon;
/**
* Sets the {@link ThreadFactory} to be wrapped by the new {@code
* BasicThreadFactory}.
*
* @param factory the wrapped {@link ThreadFactory} (must not be
* null)
* @return a reference to this {@link Builder}
* @throws NullPointerException if the passed in {@link ThreadFactory}
* is null
*/
public Builder wrappedFactory(final ThreadFactory factory) {
Objects.requireNonNull(factory, "factory");
wrappedFactory = factory;
return this;
}
/**
* Sets the naming pattern to be used by the new {@code
* BasicThreadFactory}.
*
* @param pattern the naming pattern (must not be null)
* @return a reference to this {@link Builder}
* @throws NullPointerException if the naming pattern is null
*/
public Builder namingPattern(final String pattern) {
Objects.requireNonNull(pattern, "pattern");
namingPattern = pattern;
return this;
}
/**
* Sets the daemon flag for the new {@link BasicThreadFactory}. If this
* flag is set to true the new thread factory will create daemon
* threads.
*
* @param daemon the value of the daemon flag
* @return a reference to this {@link Builder}
*/
public Builder daemon(final boolean daemon) {
this.daemon = Boolean.valueOf(daemon);
return this;
}
/**
* Sets the priority for the threads created by the new {@code
* BasicThreadFactory}.
*
* @param priority the priority
* @return a reference to this {@link Builder}
*/
public Builder priority(final int priority) {
this.priority = Integer.valueOf(priority);
return this;
}
/**
* Sets the uncaught exception handler for the threads created by the
* new {@link BasicThreadFactory}.
*
* @param handler the {@link UncaughtExceptionHandler} (must not be
* null)
* @return a reference to this {@link Builder}
* @throws NullPointerException if the exception handler is null
*/
public Builder uncaughtExceptionHandler(
final Thread.UncaughtExceptionHandler handler) {
Objects.requireNonNull(handler, "handler");
exceptionHandler = handler;
return this;
}
/**
* Resets this builder. All configuration options are set to default
* values. Note: If the {@link #build()} method was called, it is not
* necessary to call {@code reset()} explicitly because this is done
* automatically.
*/
public void reset() {
wrappedFactory = null;
exceptionHandler = null;
namingPattern = null;
priority = null;
daemon = null;
}
/**
* Creates a new {@link BasicThreadFactory} with all configuration
* options that have been specified by calling methods on this builder.
* After creating the factory {@link #reset()} is called.
*
* @return the new {@link BasicThreadFactory}
*/
@Override
public BasicThreadFactory build() {
final BasicThreadFactory factory = new BasicThreadFactory(this);
reset();
return factory;
}
}
}