org.threeten.bp.zone.ZoneRulesInitializer.scala Maven / Gradle / Ivy
/*
* 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
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package org.threeten.bp.zone
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.
*/
abstract class ZoneRulesInitializer {
/**
* 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 def initializeProviders(): Unit
}
object 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.
*/
lazy val DO_NOTHING: ZoneRulesInitializer = new DoNothingZoneRulesInitializer()
private lazy val INITIALIZED: AtomicBoolean = new AtomicBoolean(false)
private lazy val INITIALIZER: AtomicReference[ZoneRulesInitializer] =
new AtomicReference[ZoneRulesInitializer]()
// -----------------------------------------------------------------------
// initialize the providers
def initialize(): Unit = {
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()
}
/**
* 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
*/
def setInitializer(initializer: ZoneRulesInitializer): Unit = {
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"
)
}
// -----------------------------------------------------------------------
/**
* Implementation that does nothing.
*/
class DoNothingZoneRulesInitializer extends ZoneRulesInitializer {
override def initializeProviders(): Unit = {}
}
}