/*

  * 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.util.concurrent.Executors;

 import java.util.concurrent.ThreadFactory;

 import java.util.concurrent.atomic.AtomicLong;

 /**

  * <p>

  * An implementation of the {@code ThreadFactory} interface that provides some

  * configuration options for the threads it creates.

  * </p>

  * <p>

  * A {@code ThreadFactory} is used for instance by an {@code ExecutorService} to

  * create the threads it uses for executing tasks. In many cases users do not

  * have to care about a {@code ThreadFactory} because the default one used by an

  * {@code ExecutorService} will do. However, if there are special requirements

  * for the threads, a custom {@code ThreadFactory} has to be created.

  * </p>

  * <p>

  * This class provides some frequently needed configuration options for the

  * threads it creates. These are the following:

  * <ul>

  * <li>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 <em>format strings</em> 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.</li>

  * <li>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.</li>

  * <li>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.</li>

  * <li>The {@code UncaughtExceptionHandler} for the thread. This handler is

  * called if an uncaught exception occurs within the thread.</li>

  * </ul>

  * </p>

  * <p>

  * {@code 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 {@code ThreadFactory} is

  * used.

  * </p>

  * <p>

  * Instances of {@code BasicThreadFactory} are not created directly, but the

  * nested {@code 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 {@code BasicThreadFactory} is created and

  * installed in an {@code ExecutorService}:

  *

  * <pre>

  * // 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);

  * </pre>

  * </p>

  *

  * @since 3.0

  * @version $Id: BasicThreadFactory.java 1436770 2013-01-22 07:09:45Z ggregory $

  */

 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 daemonFlag;

     /**

      * Creates a new instance of {@code ThreadFactoryImpl} and configures it

      * from the specified {@code Builder} object.

      *

      * @param builder the {@code Builder} object

      */

     private BasicThreadFactory(final Builder builder) {

         if (builder.wrappedFactory == null) {

             wrappedFactory = Executors.defaultThreadFactory();

         } else {

             wrappedFactory = builder.wrappedFactory;

         }

         namingPattern = builder.namingPattern;

         priority = builder.priority;

         daemonFlag = builder.daemonFlag;

         uncaughtExceptionHandler = builder.exceptionHandler;

         threadCounter = new AtomicLong();

     }

     /**

      * Returns the wrapped {@code ThreadFactory}. This factory is used for

      * actually creating threads. This method never returns <b>null</b>. If no

      * {@code ThreadFactory} was passed when this object was created, a default

      * thread factory is returned.

      *

      * @return the wrapped {@code ThreadFactory}

      */

     public final ThreadFactory getWrappedFactory() {

         return wrappedFactory;

     }

     /**

      * Returns the naming pattern for naming newly created threads. Result can

      * be <b>null</b> 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 <b>true</b>, this factory object

      * calls {@code setDaemon(true)} on the newly created threads. Result can be

      * <b>null</b> if no daemon flag was provided at creation time.

      *

      * @return the daemon flag

      */

     public final Boolean getDaemonFlag() {

         return daemonFlag;

     }

     /**

      * Returns the priority of the threads created by this factory. Result can

      * be <b>null</b> if no priority was specified.

      *

      * @return the priority for newly created threads

      */

     public final Integer getPriority() {

         return priority;

     }

     /**

      * Returns the {@code UncaughtExceptionHandler} for the threads created by

      * this factory. Result can be <b>null</b> if no handler was provided.

      *

      * @return the {@code 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 r the {@code Runnable} to be executed by the new thread

      * @return the newly created thread

      */

     @Override

     public Thread newThread(final Runnable r) {

         final Thread t = getWrappedFactory().newThread(r);

         initializeThread(t);

         return t;

     }

     /**

      * 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 t the thread to be initialized

      */

     private void initializeThread(final Thread t) {

         if (getNamingPattern() != null) {

             final Long count = Long.valueOf(threadCounter.incrementAndGet());

             t.setName(String.format(getNamingPattern(), count));

         }

         if (getUncaughtExceptionHandler() != null) {

             t.setUncaughtExceptionHandler(getUncaughtExceptionHandler());

         }

         if (getPriority() != null) {

             t.setPriority(getPriority().intValue());

         }

         if (getDaemonFlag() != null) {

             t.setDaemon(getDaemonFlag().booleanValue());

         }

     }

     /**

      * <p>

      * A <em>builder</em> class for creating instances of {@code

      * BasicThreadFactory}.

      * </p>

      * <p>

      * Using this builder class instances of {@code BasicThreadFactory} can be

      * created and initialized. The class provides methods that correspond to

      * the configuration options supported by {@code BasicThreadFactory}. Method

      * chaining is supported. Refer to the documentation of {@code

      * BasicThreadFactory} for a usage example.

      * </p>

      *

      * @version $Id: BasicThreadFactory.java 1436770 2013-01-22 07:09:45Z ggregory $

      */

     public static class Builder 

         implements org.apache.commons.lang3.builder.Builder<BasicThreadFactory> {

         /** 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 daemonFlag;

         /**

          * Sets the {@code ThreadFactory} to be wrapped by the new {@code

          * BasicThreadFactory}.

          *

          * @param factory the wrapped {@code ThreadFactory} (must not be

          * <b>null</b>)

          * @return a reference to this {@code Builder}

          * @throws NullPointerException if the passed in {@code ThreadFactory}

          * is <b>null</b>

          */

         public Builder wrappedFactory(final ThreadFactory factory) {

             if (factory == null) {

                 throw new NullPointerException(

                         "Wrapped ThreadFactory must not be null!");

             }

             wrappedFactory = factory;

             return this;

         }

         /**

          * Sets the naming pattern to be used by the new {@code

          * BasicThreadFactory}.

          *

          * @param pattern the naming pattern (must not be <b>null</b>)

          * @return a reference to this {@code Builder}

          * @throws NullPointerException if the naming pattern is <b>null</b>

          */

         public Builder namingPattern(final String pattern) {

             if (pattern == null) {

                 throw new NullPointerException(

                         "Naming pattern must not be null!");

             }

             namingPattern = pattern;

             return this;

         }

         /**

          * Sets the daemon flag for the new {@code BasicThreadFactory}. If this

          * flag is set to <b>true</b> the new thread factory will create daemon

          * threads.

          *

          * @param f the value of the daemon flag

          * @return a reference to this {@code Builder}

          */

         public Builder daemon(final boolean f) {

             daemonFlag = Boolean.valueOf(f);

             return this;

         }

         /**

          * Sets the priority for the threads created by the new {@code

          * BasicThreadFactory}.

          *

          * @param prio the priority

          * @return a reference to this {@code Builder}

          */

         public Builder priority(final int prio) {

             priority = Integer.valueOf(prio);

             return this;

         }

         /**

          * Sets the uncaught exception handler for the threads created by the

          * new {@code BasicThreadFactory}.

          *

          * @param handler the {@code UncaughtExceptionHandler} (must not be

          * <b>null</b>)

          * @return a reference to this {@code Builder}

          * @throws NullPointerException if the exception handler is <b>null</b>

          */

         public Builder uncaughtExceptionHandler(

                 final Thread.UncaughtExceptionHandler handler) {

             if (handler == null) {

                 throw new NullPointerException(

                         "Uncaught exception handler must not be null!");

             }

             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;

             daemonFlag = null;

         }

         /**

          * Creates a new {@code 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 {@code BasicThreadFactory}

          */

         @Override

         public BasicThreadFactory build() {

             final BasicThreadFactory factory = new BasicThreadFactory(this);

             reset();

             return factory;

         }

     }

 }