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/*
* Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of JSR-310 nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.threeten.bp.zone;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
/**
* Controls how the time-zone rules are initialized.
*
* The default behavior is to use {@link ServiceLoader} to find instances of {@link ZoneRulesProvider}.
* Use the {@link #setInitializer(ZoneRulesInitializer)} method to replace this behavior.
* The initializer instance must perform the work of creating the {@code ZoneRulesProvider} within
* the {@link #initializeProviders()} method to ensure that the provider is not initialized too early.
*
* The initializer must be set before class loading of any other ThreeTen-Backport class to have any effect!
*
* This class has been added primarily for the benefit of Android.
*/
public abstract class ZoneRulesInitializer {
/**
* An instance that does nothing.
* Call {@link #setInitializer(ZoneRulesInitializer)} with this instance to
* block the service loader search. This will leave the system with no providers.
*/
public static final ZoneRulesInitializer DO_NOTHING = new DoNothingZoneRulesInitializer();
private static final AtomicBoolean INITIALIZED = new AtomicBoolean(false);
private static final AtomicReference INITIALIZER = new AtomicReference();
/**
* Sets the initializer to use.
*
* This can only be invoked before the {@link ZoneRulesProvider} class is loaded.
* Invoking this method at a later point will throw an exception.
*
* @param initializer the initializer to use
* @throws IllegalStateException if initialization has already occurred or another initializer has been set
*/
public static void setInitializer(ZoneRulesInitializer initializer) {
if (INITIALIZED.get()) {
throw new IllegalStateException("Already initialized");
}
if (!INITIALIZER.compareAndSet(null, initializer)) {
throw new IllegalStateException("Initializer was already set, possibly with a default during initialization");
}
}
//-----------------------------------------------------------------------
// initialize the providers
static void initialize() {
if (INITIALIZED.getAndSet(true)) {
throw new IllegalStateException("Already initialized");
}
// Set the default initializer if none has been provided yet.
INITIALIZER.compareAndSet(null, new ServiceLoaderZoneRulesInitializer());
INITIALIZER.get().initializeProviders();
}
/**
* Initialize the providers.
*
* The implementation should perform whatever work is necessary to initialize the providers.
* This will result in one or more calls to {@link ZoneRulesProvider#registerProvider(ZoneRulesProvider)}.
*
* It is vital that the instance of {@link ZoneRulesProvider} is not created until this method is invoked.
*
* It is guaranteed that this method will be invoked once and only once.
*/
protected abstract void initializeProviders();
//-----------------------------------------------------------------------
/**
* Implementation that does nothing.
*/
static class DoNothingZoneRulesInitializer extends ZoneRulesInitializer {
@Override
protected void initializeProviders() {
}
}
/**
* Implementation that uses the service loader.
*/
static class ServiceLoaderZoneRulesInitializer extends ZoneRulesInitializer {
@Override
protected void initializeProviders() {
ServiceLoader loader = ServiceLoader.load(ZoneRulesProvider.class, ZoneRulesProvider.class.getClassLoader());
for (ZoneRulesProvider provider : loader) {
try {
ZoneRulesProvider.registerProvider(provider);
} catch (ServiceConfigurationError ex) {
if (!(ex.getCause() instanceof SecurityException)) {
throw ex;
}
}
}
}
}
}