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Java 1.8+ Library with tons of utility classes required in all projects
There is a newer version: 11.1.10
/*
 * Copyright (C) 2014-2022 Philip Helger (www.helger.com)
 * philip[at]helger[dot]com
 *
 * Licensed 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 com.helger.commons.thirdparty;

import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.ELockType;
import com.helger.commons.annotation.MustBeLocked;
import com.helger.commons.annotation.ReturnsMutableCopy;
import com.helger.commons.annotation.Singleton;
import com.helger.commons.collection.impl.CommonsLinkedHashSet;
import com.helger.commons.collection.impl.ICommonsOrderedSet;
import com.helger.commons.concurrent.SimpleReadWriteLock;
import com.helger.commons.lang.ServiceLoaderHelper;
import com.helger.commons.state.EChange;

/**
 * This class manages all registered third party modules
 *
 * @author Philip Helger
 */
@ThreadSafe
@Singleton
public final class ThirdPartyModuleRegistry
{
  private static final class SingletonHolder
  {
    private static final ThirdPartyModuleRegistry INSTANCE = new ThirdPartyModuleRegistry ();
  }

  private static final Logger LOGGER = LoggerFactory.getLogger (ThirdPartyModuleRegistry.class);
  private static boolean s_bDefaultInstantiated = false;

  private final SimpleReadWriteLock m_aRWLock = new SimpleReadWriteLock ();
  @GuardedBy ("m_aRWLock")
  private final ICommonsOrderedSet  m_aModules = new CommonsLinkedHashSet <> ();

  private ThirdPartyModuleRegistry ()
  {
    reinitialize ();
  }

  public static boolean isInstantiated ()
  {
    return s_bDefaultInstantiated;
  }

  @Nonnull
  public static ThirdPartyModuleRegistry getInstance ()
  {
    final ThirdPartyModuleRegistry ret = SingletonHolder.INSTANCE;
    s_bDefaultInstantiated = true;
    return ret;
  }

  @Nonnull
  @MustBeLocked (ELockType.WRITE)
  private EChange _registerThirdPartyModule (@Nonnull final IThirdPartyModule aModule)
  {
    ValueEnforcer.notNull (aModule, "Module");

    return m_aModules.addObject (aModule);
  }

  @Nonnull
  public EChange registerThirdPartyModule (@Nonnull final IThirdPartyModule aModule)
  {
    return m_aRWLock.writeLockedGet ( () -> _registerThirdPartyModule (aModule));
  }

  @Nonnull
  @ReturnsMutableCopy
  public ICommonsOrderedSet  getAllRegisteredThirdPartyModules ()
  {
    return m_aRWLock.readLockedGet (m_aModules::getClone);
  }

  @Nonnegative
  public int getRegisteredThirdPartyModuleCount ()
  {
    return m_aRWLock.readLockedInt (m_aModules::size);
  }

  public void reinitialize ()
  {
    m_aRWLock.writeLocked ( () -> {
      m_aModules.clear ();

      // Load all SPI implementations
      for (final IThirdPartyModuleProviderSPI aTPM : ServiceLoaderHelper.getAllSPIImplementations (IThirdPartyModuleProviderSPI.class))
      {
        final IThirdPartyModule [] aModules = aTPM.getAllThirdPartyModules ();
        if (aModules != null)
          for (final IThirdPartyModule aModule : aModules)
            _registerThirdPartyModule (aModule);
      }
    });

    if (LOGGER.isDebugEnabled ())
      LOGGER.debug ("Reinitialized " + ThirdPartyModuleRegistry.class.getName ());
  }
}